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Although chimeric antigen receptor T (CART)–cell therapy has been successful in treating certain hematologic malignancies, wider adoption of CART-cell therapy is limited because of minimal activity in solid tumors and development of life-threatening toxicities, including cytokine release syndrome (CRS). There is a lack of a robust, clinically relevant imaging platform to monitor in vivo expansion and trafficking to tumor sites. To address this, we utilized the sodium iodide symporter (NIS) as a platform to image and track CART cells. We engineered CD19-directed and B-cell maturation antigen (BCMA)–directed CART cells to express NIS (NIS+CART19 and NIS+BCMA-CART, respectively) and tested the sensitivity of 18F-TFB-PET to detect trafficking and expansion in systemic and localized tumor models and in a CART-cell toxicity model. NIS+CART19 and NIS+BCMA-CART cells were generated through dual transduction with two vectors and demonstrated exclusive 125I uptake in vitro. 18F-TFB-PET detected NIS+CART cells in vivo to a sensitivity level of 40,000 cells. 18F-TFB-PET confirmed NIS+BCMA-CART-cell trafficking to the tumor sites in localized and systemic tumor models. In a xenograft model for CART-cell toxicity, 18F-TFB-PET revealed significant systemic uptake, correlating with CART-cell in vivo expansion, cytokine production, and development of CRS-associated clinical symptoms. NIS provides a sensitive, clinically applicable platform for CART-cell imaging with PET scan. 18F-TFB-PET detected CART-cell trafficking to tumor sites and in vivo expansion, correlating with the development of clinical and laboratory markers of CRS. These studies demonstrate a noninvasive, clinically relevant method to assess CART-cell functions in vivo.

Through our involvement in KEYNOTE-059, we unexpectedly observed durable responses in two patients with metastatic gastroesophageal adenocarcinoma (mGEA) who received ramucirumab (anti-VEGFR-2)/paclitaxel after immune checkpoint inhibition (ICI). To assess the reproducibility of this observation, we piloted an approach to administer ramucirumab/ paclitaxel after ICI in more patients, and explored changes in the immune microenvironment. Nineteen consecutive patients with mGEA received ICI followed by ramucirumab/paclitaxel. Most (95%) did not respond to ICI, yet after irRECIST-defined progression on ICI, all patients experienced tumor size reduction on ramucirumab/paclitaxel. The objective response rate (ORR) and progression-free survival (PFS) on ramucirumab/paclitaxel after ICI were higher than on the last chemotherapy before ICI in the same group of patients (ORR, 58.8% vs 11.8%; PFS 12.2 vs 3.0 months; respectively). Paired tumor biopsies examined by imaging mass cytometry showed a median 5.5-fold (range 4–121) lower frequency of immunosuppressive forkhead box P3+ regulatory T cells with relatively preserved CD8+ T cells, post-treatment versus pre-treatment (n = 5 pairs). We then compared the outcomes of these 19 patients with a separate group who received ramucirumab/paclitaxel without preceding ICI (n = 68). Median overall survival on ramucirumab/paclitaxel was longer with (vs without) immediately preceding ICI (14.8 vs 7.4 months) including after multivariate analysis, as was PFS. In our small clinical series, outcomes appeared improved on anti-VEGFR-2/paclitaxel treatment when preceded by ICI, in association with alterations in the immune microenvironment. However, further investigation is needed to determine the generalizability of these data. Prospective clinical trials to evaluate sequential treatment with ICI followed by anti-VEGF(R)/taxane are underway.

Chimeric antigen receptor (CAR) T cell therapy has yielded unprecedented outcomes in some patients with hematological malignancies; however, inhibition by the tumor microenvironment has prevented the broader success of CART cell therapy. We used chronic lymphocytic leukemia (CLL) as a model to investigate the interactions between the tumor microenvironment and CART cells. CLL is characterized by an immunosuppressive microenvironment, an abundance of systemic extracellular vesicles (EVs), and a relatively lower durable response rate to CART cell therapy. In this study, we characterized plasma EVs from untreated CLL patients and identified their leukemic cell origin. CLL-derived EVs were able to induce a state of CART cell dysfunction characterized by phenotypical, functional, and transcriptional changes of exhaustion. We demonstrate that, specifically, PD-L1(+) CLL-derived EVs induce CART cell exhaustion. In conclusion, we identify an important mechanism of CART cell exhaustion induced by EVs from CLL patients.

In patients with metastatic melanoma, high blood levels of galectin-9 are correlated with worse overall survival and a bias towards a Th2 inflammatory state supportive of tumor growth. Although galectin-9 signaling through TIM3 on T cells has been described, less is known about the interaction of galectin-9 with macrophages. We aimed to determine whether galectin-9 is a binding partner of CD206 on macrophages and whether the result of this interaction is tumor-supportive. It was determined that incubation of CD68+ macrophages with galectin-9 or anti-CD206 blocked target binding and that both CD206 and galectin-9 were detected by immunoprecipitation of cell lysates. CD206 and galectin-9 had a binding affinity of 2.8 × 10-7 m. Galectin-9 causes CD206+ macrophages to make significantly more FGF2 and monocyte chemoattractant protein (MCP-1), but less macrophage-derived chemokine (MDC). Galectin-9 had no effect on classical monocyte subsets, but caused expansion of the non-classical populations. Lastly, there was a positive correlation between increasing numbers of CD206 macrophages and galectin-9 expression in tumors, and high levels of CD206 macrophages correlated negatively with melanoma survival. These results indicate that galectin-9 binds to CD206 on M2 macrophages, which appear to drive angiogenesis and the production of chemokines that support tumor growth and poor patient prognoses. Targeting this interaction systemically through circulating monocytes may therefore be a novel way to improve local anti-tumor effects by macrophages. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

In the original version of [this article][1] ([1][2]), the test groups in Fig. 3B were incorrectly listed. The error has been corrected in the latest online HTML and PDF versions of the article. The authors regret this error. 1. 1.[↵][3]1. Nevala WK, 2. Buhrow SA, 3. Knauer DJ

Galectin-9, a β-galactoside-binding protein, is defined as a negative regulator of T helper 1 (Th1) immune responses, favoring Th2 bias. Systemic immunity in patients with metastatic melanoma is predominantly Th2 biased. We hypothesized that galectin-9 can modulate systemic immunity toward Th2 polarization in patients with advanced melanoma. The presence or concentration of galectin-9 was assessed in tumors and plasma, in patients with metastatic melanoma. The immunomodulatory function of galectin-9 was determined by exposing human peripheral blood mononuclear cells to galectin-9 in vitro. Galectin-9 was expressed in 57% of tumors and was significantly (3.6-fold) increased in the plasma of patients with advanced melanoma compared with healthy controls (P

Chimeric antigen receptor T (CAR-T) cell therapy is a new pillar in cancer therapeutics; however, its application is limited by the associated toxicities. These include cytokine release syndrome (CRS) and neurotoxicity. Although the IL-6R antagonist tocilizumab is approved for treatment of CRS, there is no approved treatment of neurotoxicity associated with CD19-targeted CAR-T (CART19) cell therapy. Recent data suggest that monocytes and macrophages contribute to the development of CRS and neurotoxicity after CAR-T cell therapy. Therefore, we investigated neutralizing granulocyte-macrophage colony-stimulating factor (GM-CSF) as a potential strategy to manage CART19 cell–associated toxicities. In this study, we show that GM-CSF neutralization with lenzilumab does not inhibit CART19 cell function in vitro or in vivo. Moreover, CART19 cell proliferation was enhanced and durable control of leukemic disease was maintained better in patient-derived xenografts after GM-CSF neutralization with lenzilumab. In a patient acute lymphoblastic leukemia xenograft model of CRS and neuroinflammation (NI), GM-CSF neutralization resulted in a reduction of myeloid and T cell infiltration in the central nervous system and a significant reduction in NI and prevention of CRS. Finally, we generated GM-CSF–deficient CART19 cells through CRISPR/Cas9 disruption of GM-CSF during CAR-T cell manufacturing. These GM-CSFk/o CAR-T cells maintained normal functions and had enhanced antitumor activity in vivo, as well as improved overall survival, compared with CART19 cells. Together, these studies illuminate a novel approach to abrogate NI and CRS through GM-CSF neutralization, which may potentially enhance CAR-T cell function. Phase 2 studies with lenzilumab in combination with CART19 cell therapy are planned.

e15184 Background: Clinical responses to anti-PD1 immunotherapy in patients with metastatic melanoma (MM) remain challenging to predict. This clinical heterogeneity is also reflected in the tumor-immune microenvironment among patients and within a single tumor lesion. With the emergence of multiplex imaging platforms, defining complex phenotypes at single cell resolution has become possible. Here, we sought to objectively quantify paracrine tumor-immune interactions contributing to the variable clinical responses observed in patients receiving anti-PD1 therapy. Methods: Excisional lymph node (LN) biopsies were obtained from treatment-naïve patients with MM who underwent subsequent anti-PD1 therapy. A single 5µm section of LN tissue was used to assess a 42 analyte panel by multiplex immunofluorescence. From 30 LN samples, 418 fields of view (FOVs) were selected resulting in 14,360 high-resolution images of 4 anatomical subregions: tumor core, tumor-immune interface, tumor infiltrate and adjacent immune stroma. Following image processing, we developed an adaptive classification for tumor-centric cellular neighborhoods (TCCN) to identify and quantify critical paracrine interactions within the tumor-immune microenvironment. Results: Stratification based on responsiveness to anti-PD1 therapy resulted in 4 complete responders (CR) and 12 non-responders (NR) at 12-week follow-up. From 126 FOVs, we defined the cellular composition of 197,865 TCCN across patients based on clinical response and LN subregions. Overall, the percentage of TCCN devoid of any T cells, B cells or macrophages was significantly higher in NR compared to CR irrespective of subregion. However, other markers differentiated TCCN based on subregion. Specifically in CR, tumor core regions were enriched for CD8 T cells, while enrichment for B cells and endothelial cells was demonstrated at the tumor-immune interface. Strikingly, tumor infiltrate regions demonstrate robust immune reactivity with enrichment for M1 polarized macrophages, NK cells and B cells in CR compared to NR. Complete data from the 30 patient cohort across 418 FOVs will be presented. Conclusions: Taken together, this data suggests cellular composition of TCCN across subregions of the LN is dynamic within a single metastatic site. In this small cohort, we introduce a formalized stratification to quantify and classify critical paracrine interactions within the immune-tumor microenvironment with the potential to inform clinical responsiveness to therapy.

e18097 Background: AB160 is a 160 nm nano-immunoconjugate consisting of nab-paclitaxel (NP) nanoparticles non-covalently coated with bevacizumab (BEV) for targeted delivery into tissues expressing high levels of vascular-endothelial growth factor (VEGF). Both taxanes (GOG-0129C, GOG-0126R, GOG-0127V) and BEV (GOG-0229E, AURELIA, GOG-0227C) have demonstrated clinical activity in previously treated metastatic endometrial cancer (EC), ovarian cancer (OC), and cervical cancer (CC), respectively. Methods: A 3+3 phase I trial was conducted in patients with EC, platinum-resistant OC and CC who had prior systemic treatment for metastatic disease to determine the maximum tolerated dose of AB160 administered intravenously on days 1, 8 and 15 of a 28-day cycle. The starting dose level (DL1) was NP at 125 mg/m2 with BEV at 50 mg/m2. There were 2 higher dose levels: DL2 (NP at 150 mg/m2 with BEV at 60 mg/m2) and DL3 (NP at 175 mg/m2 with BEV at 70 mg/m2). Dose limiting toxicities (DLT) included grade (G) 4 neutropenia or anemia, PLT < 25,000, serum creatinine ≥2 times baseline, G2-4 neurologic toxicity or G3-4 non-hematologic toxicities. Disease evaluations were conducted after every 2 treatment cycles using RECIST criteria. Patients were treated until disease progression or intolerability. Samples were collected for pharmacokinetic (PK) studies. Results: Nine women 41 – 74 years of age (median 57) have enrolled (5 with EC and 4 with OC); data are available for the first 8. No DLTs have been observed among the 3 women enrolled on DL1, 3 women on DL2, and 2 women on DL3. All 3 patients on DL3 continue on treatment. The other 6 patients have discontinued due to adverse reactions (3), progression (2), and patient choice (1). The median number of cycles administered is 6 (4-14). The most common severe (G3/4) toxicities include neutropenia (37.5%) and leukopenia (25%). There have been 5 partial responses (62.5%): 1 on DL1 and 2 each on DL2 and DL3. PK evaluation is pending. Conclusions: AB160 therapy is safe and demonstrates promising clinical activity in patients with previously treated metastatic gynecologic malignancies. Further clinical testing is being pursued in this patient population. Clinical trial information: NCT02020707.

Malignant melanoma is the most aggressive form of skin cancer, accounting for 10,000 deaths annually. Largely resistant to conventional cytotoxic chemotherapy and radiation, immune checkpoint blockade (ICB) therapies have revolutionized patient care, accounting for partial or complete responses in up to 70% of patients. An important aspect of cancer elimination is activation of the cytotoxic T lymphocyte (CTL) response. Recent data suggest that ICB mediated broadening of the peripheral blood CTL repertoire correlates with good clinical outcomes. Thus, recent studies in cancer immunotherapy have focused on targeting tumor neoantigens (tNeoAg) with cancer vaccines for use in combination with ICB. Computational algorithm-driven predictions of immunogenic tNeoAgs yield vast numbers of potential peptide targets, only a fraction of which may be immunogenic in patients. This likely contributed to the modest success of cancer vaccines targeting predicted, high-avidity tNeoAgs, emphasizing the importance of identifying true tumor rejection antigens, including sub-dominant antigens, outside the scope of predictive models. In addition to promoting T cell-mediated tumor rejection, ICB often comes at the expense of treatment-induced immune-related adverse effects (irAE) that frequently require discontinuation of treatment. Modulation of ICB towards antitumor immunity and away from autoimmunity may dramatically improve the therapeutic index of modern cancer therapy. This appears feasible considering the clinical observation that antitumor efficacy does not correlate with type/severity of irAE, suggesting that the mechanisms of both processes, though likely related (CTL mediated), may not be identical. We aim to identify and separate non-cross-reacting antigenic targets mediating tumor rejection from those mediating irAEs to enable therapeutic interventions that maximize the efficacy of ICB, expanding tumor-specific CTLs with vaccines while minimizing irAEs through desensitization. We have access to samples from responding/nonresponding melanoma patients subjected to ICB with varying degrees of irAEs. We have designed an experimental approach that combines established mass spectrometry and sequencing techniques to identify peptides and matching TCR clones with a novel strategy that targets the TCR-associated CD3 complex to allow inclusion of subdominant antigens in our studies. T-cell “co-potentiation” is achieved when anti-CD3 monovalent Fabs induce a conformational change in the CD3 complex that sustains the T-cell response to weak antigenic stimulation. We have successfully used anti-human CD3 Fabs to co-potentiate in vitro the activation and subsequent response to weak peptide-HLA/TCR interactions of human T cells found in PBMCs isolated from healthy donors. Our preliminary data suggest T-cell co-potentiation may allow identification of ICB-induced CTL clones specific for subdominant tNeoAgs and irAE targets in patients with melanoma undergoing active immunotherapy. Citation Format: Laura Elsbernd, Alfreda Nelson, Hien Huynh, Michele Hoffmann, Christopher Parks, Wendy Nevala, Shari Sutor, Larry Pease, Adam Schrum, Diana Gil, Svetomir N. Markovic. Co-potentiation of human T cells to identify subdominant tumor neoantigens from melanoma patients responding to immune checkpoint blockade [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B78.

A vaccine that could expand melanoma-specific T cells might reduce the risk of recurrence of resected melanoma and could provide an alternative or adjunct to standard immunotherapy options. We tested the safety and immunogenicity of a vaccine coupling a melanoma-associated peptide with a xenogenic peptide (to promote epitope spreading) and/or resiquimod (to activate antigen-presenting cells). HLA-A2-positive patients with resected stage II, III, and IV melanoma were assigned to treatment on one of three schedules. All patients received three subcutaneous doses of the peptide MART-1a mixed with Montanide. In addition, patients on schedule 1 received the xenoantigen peptide Gag267-274, patients on schedule 2 received topical resiquimod, and patients on schedule 3 received both Gag267-274 and resiquimod. Blood samples were tested for the frequency of antigen-specific T cells by tetramer assay, as well as immune cell subtypes and plasma cytokine levels. Patients enrolled from October 2012 to December 2014, with 10 patients enrolling to each schedule. The most common adverse events were injection site reaction (26 patients) and fatigue (15 patients). Tetramer analysis revealed antigen-specific responses (defined as doubling of MART-1a-specific T cells from pretreatment to post-treatment) in 20, 60, and 40% of patients treated on schedules 1, 2, and 3, respectively. Vaccine treatment consisting of MART-1a peptide, Gag267-274, Montanide, and topical resiquimod was well-tolerated. The addition of the Gag267-274 xenoantigen was not associated with an increase in the response to MART-1a, whereas use of topical resiquimod was associated with a higher frequency of MART-1a-specific T-cell responses that did not meet statistical significance.

Introduction Malignant pleural mesothelioma is a disease primarily associated with exposure to the carcinogen asbestos. Whereas other carcinogen-related tumors are associated with a high tumor mutation burden, mesothelioma is not. We sought to resolve this discrepancy. Methods We used mate-pair (n = 22), RNA (n = 28), and T cell receptor sequencing along with in silico predictions and immunologic assays to understand how structural variants of chromosomes affect the transcriptome. Results We observed that inter- or intrachromosomal rearrangements were present in every specimen and were frequently in a pattern of chromoanagenesis such as chromoplexy or chromothripsis. Transcription of rearrangement-related junctions was predicted to result in many potential neoantigens, some of which were proven to bind patient-specific major histocompatibility complex molecules and to expand intratumoral T cell clones. T cells responsive to these predicted neoantigens were also present in a patient's circulating T cell repertoire. Analysis of genomic array data from the mesothelioma cohort in The Cancer Genome Atlas suggested that multiple chromothriptic-like events negatively impact survival. Conclusions Our findings represent the discovery of potential neoantigen expression driven by structural chromosomal rearrangements. These results may have implications for the development of novel immunotherapeutic strategies and the selection of patients to receive immunotherapies.

We developed a nano-antibody targeted chemotherapy (nATC) delivery strategy in which tumor specific and clinically relevant antibodies (rituximab, anti-CD20) are non-covalently bound to the albumin scaffold of nab-paclitaxel (ABX). We define the nanoparticle formed when the 2 drugs are bound (AR160). The newly created nATC retains the cytotoxicity of ABX and CD20 affinity of rituximab in vitro. We describe the binding characteristics of the ABX and rituximab in AR160 using peptide mapping/Biacore approach. Flow-based methods, including ImageStream and nanoparticle tracking, were used to characterize the AR160 particles in vitro. A mouse model of human B-cell lymphoma was utilized to test in vivo efficacy of AR160 therapy, which suggested improved tumor targeting (biodistribution) as the most likely mechanism of AR160 therapeutic superiority over ABX or rituximab alone. These data suggest a novel platform for nATC delivery using a slight modification of existing cancer drugs with significantly improved treatment efficacy.

Evolution of melanoma from a primary tumor to widespread metastasis is crucially dependent on lymphatic spread. The mechanisms regulating the initial step in metastatic dissemination via regional lymph nodes remain largely unknown however evidence supporting the establishment of a pre-metastatic niche is evolving. We have previously described a dysfunctional immune profile including reduced expression of DC maturation markers in the first node draining from the primary tumor, the sentinel lymph node (SLN). Importantly, this phenotype is present prior to evidence of nodal metastasis. Herein, we evaluate melanoma-derived extracellular vesicles (EVs) as potential mediators of the pre-metastatic niche through cargo-specific polarization of dendritic cells (DCs). Matured in vitro in the presence of melanoma EVs, DCs show significantly impaired expression of co-stimulatory markers CD83 and CD86 compared to liposome treated DCs as well as decreased expression of Th1 polarizing cytokines Flt3L and IL15 and migration chemokines MIP1α and MIP1β. Profiling of melanoma EV cargo identified shared proteomic and RNA signatures including S100A8 and S100A9 protein cargo which in vitro compromised DC maturation similar to melanoma EVs. Early evidence demonstrates similar EVs can be isolated from human afferent lymphatic fluid ex vivo. Taken together, here we propose melanoma EV cargo as a mechanism by which DC maturation is compromised warranting further study to consider this as a potential mechanism enabled by the primary tumor to establish the pre-metastatic niche in tumor-draining SLNs of patients.

The management of patients with metastatic melanoma remains a difficult problem. Although potentially curable when diagnosed early, the median survival of patients with metastatic disease is generally

Monocytes may contribute to tumor progression in part by mediating tumor-induced immunosuppression. Alterations to the monocyte populations and functions in untreated patients with late-stage melanoma are not fully understood. To characterize these alterations, we compared the frequency, phenotype, and functional capacity of peripheral blood monocytes and other myeloid cells in untreated, newly diagnosed stage IV melanoma patients (n = 18) with those in healthy volunteers. Stage IV untreated melanoma patients exhibited a sizeable decrease in the percentage of monocytes (P < 0.0001) that included a drop in the percentage of the CD14+CD16− classical monocyte pool (P = 0.006). Although there was not a significant difference in the CD14+HLA-DRlow/− monocyte population between the patients with melanoma and the healthy volunteers, the HLA-DR levels were considerably lower in the patients' CD14+CD16+ intermediate (P < 0.0001) and CD14lowCD16+ nonclassical monocyte populations (P = 0.001). Decreased surface expression of CD86 (P = 0.0006) and TNFRII (P = 0.0001) and increased expression of tissue factor and PD-L1 (P = 0.003) were identified on monocytes from patients with melanoma. Furthermore, these monocytes had decreased ability to upregulate CD80 expression and cytokine production following stimulation with agonist of Toll-like receptor 3 (TLR3). Peripheral blood dendritic cell subsets were decreased in untreated stage IV melanoma patients. Our study demonstrates that untreated late-stage melanoma patients exhibit monocytopenia in addition to phenotypic and functional deficiencies that may negatively affect their immune function. These findings open new avenues into examining the role of monocyte populations in melanoma development. Cancer Immunol Res; 2(3); 241–8. ©2013 AACR.

A systemic analysis of the tumor-immune interactions within the heterogeneous tumor microenvironment is of particular importance for understanding the antitumor immune response. We used multiplexed immunofluorescence to elucidate cellular spatial interactions and T-cell infiltrations in metastatic melanoma tumor microenvironment. We developed two novel computational approaches that enable infiltration clustering and single cell analysis-cell aggregate algorithm and cell neighborhood analysis algorithm-to reveal and to compare the spatial distribution of various immune cells relative to tumor cell in sub-anatomic tumor microenvironment areas. We showed that the heterogeneous tumor human leukocyte antigen-1 expressions differently affect the magnitude of cytotoxic T-cell infiltration and the distributions of CD20+ B cells and CD4+FOXP3+ regulatory T cells within and outside of T-cell infiltrated tumor areas. In a cohort of 166 stage III melanoma samples, high tumor human leukocyte antigen-1 expression is required but not sufficient for high T-cell infiltration, with significantly improved overall survival. Our results demonstrate that tumor cells with heterogeneous properties are associated with differential but predictable distributions of immune cells within heterogeneous tumor microenvironment with various biological features and impacts on clinical outcomes. It establishes tools necessary for systematic analysis of the tumor microenvironment, allowing the elucidation of the "homogeneous patterns" within the heterogeneous tumor microenvironment.

e21058 Background: Recent clinical advances in cancer immuno-therapeutics underscore the need for improved understanding of the complex relationship between cancer and the multiple, multi-functional, inter-dependent, cellular and humoral mediators/regulators of the human immune system. This will lead to improvements in the efficacy of existing immune therapies (patient selection; drug combinations) and insight into new therapeutic targets that may significantly reduce the time to new therapeutics discoveries capable of meaningful clinical impacts. Methods: A systems analysis approach (Cancer Immune Control Dynamics, CICD) attempts to identify the differences between systemic immune homeostasis of healthy volunteers versus patients with metastatic malignant melanoma based on serial measurements of a set of conventional peripheral blood biomarkers of immune function (15 cell subsets and 35 cytokines) assessed daily over 7-10 days. The modeling strategy takes aerospace engineering control theory and system identification algorithms to analyze the state of an individual’s immune system based on the biomarkers’ dynamic non-linear oscillatory behaviors. The analysis framework builds on the classical predator-prey equations commonly used to model biological system dynamics. Tens of thousands of biologically possible biomarker interactions are modeled by a set of matrix equations that creates a system interaction model. CICD quantifies the system equations with biomarker values and solves it to measure the interactions. Results: Quantification of thousands of unique biomarker relationships per participant enables classification based on their immune profile rather than their clinical diagnosis and a basis for a visualization of a person’s immunity state. Conclusions: Results provide initial evidence that a model-based analysis of serially collected biomarker data can lead to biological insights into human immunity, of potential benefit in clinical decisions. It is anticipated that CICD-based capabilities will provide tools to specifically address cancer and treatment modulated (immune checkpoint inhibitors) parameters of human immunity, revealing clinically relevant biological interactions.

Chimeric antigen receptor T-cell therapy (CART) is limited by the development of cytokine release syndrome (CRS) and neurotoxicity (NT). CRS is related to extreme elevation of cytokines and massive T cell expansion. Preliminary studies suggest that NT might be mediated by myeloid cells that cross the blood brain barrier. This is supported by correlative analysis from CART19 pivotal trials where CD14+ cell numbers were increased in the cerebrospinal fluid of patients that developed severe NT (Locke et al, ASH 2017). Thus, we aimed to investigate the role of GM-CSF neutralization in preventing CRS and NT after CART cell therapy via monocyte control. The human GM-CSF neutralizing antibody lenzilumab (Humanigen, Burlingame, California), which has been shown to be safe in phase II clinical trials, does not impair CART cell function in vitro (10 ug/mL) when CART19 cells are stimulated with the CD19+ Luciferase+ acute lymphoblastic leukemia (ALL) cell line NALM6. Lenzilumab results in enhanced CART cell antigen specific proliferation in the presence of monocytes. In vivo, NOD-SCID-g−/− mice were engrafted with high disease burdens of NALM6 and treated with low doses of CART19 or control T cells, in combination with lenzilumab or isotype control antibody. The combination of CART19 and lenzilumab does not impair CART cell activity in vivo (Fig 1A). The impact of GM-CSF neutralization on CART toxicities in a novel patient derived xenograft model was explored. NOD-SCID-g−/− mice were engrafted with primary ALL blasts (1-3 × 106 cells). Mice were treated with high doses of CART19 cells (2-5 × 106 iv) and developed CART cell related toxicities. The combination of CART19, lenzilumab (to neutralize human GM-CSF), and murine GM-CSF blocking antibody (to neutralize mouse GM-CSF) resulted in prevention of weight loss (Fig 1B), decrease in critical myeloid cytokines (Fig 1C-D), reduction of cerebral edema (Fig 1E), enhanced leukemic disease control in the brain (Fig 1F), and reduction in brain macrophages (Fig 1G). As CRISPR/Cas9 gene editing of the GM-CSF gene during the process of CART cell manufacturing would result in CART cells with innately reduced secretion of GM-CSF, we designed guide RNA targeting exon 3 of the GM-CSF gene to generate GM-CSFk/o CART19 cells. These CARTs produce significantly less GM-CSF upon activation but other T cell cytokine production is not inhibited (Fig 1H). Using the NALM6 high tumor burden relapse xenograft model as described above, GM-CSFk/o CART19 cells resulted in slightly enhanced disease control compared to CART19 cells (Fig 1I). These studies illuminate a novel approach to abrogate NT and CRS through GM-CSF blockade that also potentially enhances CART cell functions. Based on these results, we have designed a phase II clinical trial using lenzilumab as a modality to prevent CART related toxicities in patients with diffuse large B cell lymphoma.

Introduction Malignant pleural effusions (MPEs) are a significant source of cancer morbidity and mortality. Currently there is no cure for MPEs and treatments only palliate the symptoms. The purpose of this study was to determine if there are differences in markers of angiogenesis and immune phenotypes between adenocarcinoma-induced MPEs and benign pleural effusions (BPEs). Methods Pleural effusions were collected from patients with MPEs and BPEs. Cells were isolated from effusions and characterized using fluorescent cell sorting (FACS). Pleural effusions were evaluated by ELISA for VEGF-A. An angiogenesis protein array was completed to compare protein expression in malignant and non-malignant effusions. Results FACS analysis demonstrated lower accumulation of cytotoxic T-cells and significantly higher accumulation of monocytes, dendritic cells, mesothelial and tumor cells in MPEs compared to benign pleural effusions. MPEs were found to have 77-fold higher VEGF-A levels compared to BPEs. The angiogenesis protein array demonstrated elevated levels of pro-angiogenic factors VEGF-A, CXCL4 and MMP-8, and low levels of pro-inflammatory cytokines IL-8, MCP-1, and TGF-β1 in MPEs. Conclusions MPE is biased toward a Th2 dominant state. There is an increase in expression of VEGF-A and other pro-angiogenic factors in MPE. These data suggest there is a role for anti-angiogenesis therapy in patients with MPEs.

Skin cancer affects more individuals in the USA than any other malignancy and malignant melanoma is particularly deadly because of its metastatic potential. Melanoma has been recognized as one of the most immunogenic malignancies; therefore, understanding the mechanisms of tumor-immune interaction is key for developing more efficient treatments. As the tumor microenvironment shows an immunosuppressive action, immunotherapeutic agents promoting endogenous immune response to cancer have been tested (interleukin-2, anticytotoxic-T-lymphocyte-associated antigen 4, and antiprogrammed cell death protein 1 monoclonal antibodies) as well as combinations of cytotoxic chemotherapy agents and inhibitors of angiogenesis (taxol/carboplatin/avastin). However, clinical outcomes are variable, with only a minority of patients achieving durable complete responses. The variability of immune homeostasis, which may be more active or more tolerant at any given time, in cancer patients and the interaction of the immune system with the tumor could explain the inconsistency in clinical outcomes among these patients. Recently, the role of the lymphocyte-to-monocyte-ratio (LMR) in the peripheral blood has been investigated and has been proven to be an independent predictor of survival in different hematological malignancies and in solid tumors. In melanoma, our group has validated the significance of LMR as a predictor of relapse after resection of advanced melanoma. In this study, we examined the dynamics in the immune system of patients with advanced melanoma by performing serial multiday concentration measurements of cytokines and immune cell subsets in the peripheral blood. The analysis of outcomes of chemotherapy administration as related to LMR on the day of treatment initiation showed that progression-free survival was improved in the patients who received chemotherapy on the day when LMR was elevated.

Immune checkpoint therapy with PD-1 blockade has emerged as an effective therapy for many advanced cancers; however, only a small fraction of patients achieve durable responses. To date, there is no validated blood-based means of predicting the response to PD-1 blockade. We report that Bim is a downstream signaling molecule of the PD-1 pathway, and its detection in T cells is significantly associated with expression of PD-1 and effector T cell markers. High levels of Bim in circulating tumor-reactive (PD-1+CD11ahiCD8+) T cells were prognostic of poor survival in patients with metastatic melanoma who did not receive anti–PD-1 therapy and were also predictive of clinical benefit in patients with metastatic melanoma who were treated with anti–PD-1 therapy. Moreover, this circulating tumor-reactive T cell population significantly decreased after successful anti–PD-1 therapy. Our study supports a crucial role of Bim in both T cell activation and apoptosis as regulated by PD-1 and PD-L1 interactions in effector CD8+ T cells. Measurement of Bim levels in circulating T cells of patients with cancer may provide a less invasive strategy to predict and monitor responses to anti–PD-1 therapy, although future prospective analyses are needed to validate its utility.

Thus far, peptide vaccines used to stimulate tumor-specific immune responses in patients with melanoma have been largely unsuccessful. Granulocyte-macrophage colony-stimulating factor and interleukin-2 are immune-potentiating cytokines that have improved vaccine responses in preclinical models. We hypothesized that higher doses of granulocyte-macrophage colony-stimulating factor and addition of low-dose interleukin-2 might augment responses to vaccine antigens. Patients with resected stage II, III, or IV melanoma were treated with vaccines containing three melanoma-associated peptides [MART-1a, gp100(207-217), and survivin], along with 300 or 500 mcg granulocyte-macrophage colony-stimulating factor in Montanide ISA. Cohorts of patients received low-dose subcutaneous interleukin-2 on days 7-20 after vaccination. Induction of a response was defined as either doubling of cytotoxic T lymphocyte frequency from baseline or increase in frequency from undetectable (

Purpose: Metastatic cancer patients exhibit systemic dysregulation of immune polarity and are biased toward Th-2 immune responses. This is due, at least in part, to effects of VEGF on antigen presenting cell (APC) function. We therefore compared immune polarity changes in mouse models of cancer with those seen in human patients. Experimental Design: We measured plasma levels of vascular growth factors and multiple cytokines via ELISA and multiplex analysis in mice with transplantable and spontaneous tumors. We compared immune cell subsets in naive and vaccinated mice with and without tumors. We assessed cytokine immune responses by multiplex analysis. Finally, we assessed gene expression and receptor surface expression in response to VEGF in mouse and human APCs. Results: Although human patients have elevated plasma cytokines and altered immune polarity in response to antigen, mice have minimal immune abnormalities. Mouse VEGF does not mediate immune repolarization in vitro. Human but not mouse APCs upregulate VEGFR2 and downregulate interleukin (IL)-12β in response to VEGF. Conclusions: Whereas humans with metastatic cancer demonstrate dysregulated immune polarity in response to excess plasma VEGF, tumor mice do not. This appears to be due to differences in APC responses to VEGF stimulation. Differential immune effects of VEGF may represent a key species difference in the context of translation of preclinical cancer immunotherapeutics into early clinical testing. Clin Cancer Res; 17(7); 1776–83. ©2011 AACR.

Despite its efficacy, chimeric antigen receptor T-cell therapy (CART) is limited by the development of cytokine release syndrome (CRS) and neurotoxicity (NT). While CRS is related to extreme elevation of cytokines and massive T cell expansion, the exact mechanisms for NT have not yet been elucidated. Preliminary studies suggest that NT might be mediated by myeloid cells that cross the blood brain barrier. This is supported by correlative analysis from CART19 pivotal trials where CD14+ cell numbers were increased in the cerebrospinal fluid of patients that developed severe NT (Locke et al, ASH 2017). Therefore, we aimed to investigate the role of GM-CSF neutralization in preventing CRS and NT after CART cell therapy via monocyte control. First, we investigated the effect of GM-CSF blockade on CART cell effector functions. Here, we used the human GM-CSF neutralizing antibody (lenzilumab, Humanigen, Burlingame, California) that has been shown to be safe in phase II clinical trials. Lenzilumab (10 ug/kg) neutralizes GM-CSF when CART19 cells are stimulated with the CD19+ Luciferase+ acute lymphoblastic leukemia (ALL) cell line NALM6, but does not impair CART cell function in vitro. We have found that malignancy associated macrophages reduce CART proliferation. GM-CSF neutralization with lenzilumab results in enhanced CART cell antigen specific proliferation in the presence of monocytes. To confirm this in vivo, NOD-SCID-g-/- mice were engrafted with high disease burdens of NALM6 and treated with low doses of CART19 or control T cells (to induce tumor relapse), in combination with lenzilumab or isotype control antibody. The combination of CART19 and lenzilumab resulted in significant anti-tumor activity and overall survival benefit compared to control T cells (Fig 1A), similar to mice treated with CART19 combined with isotype control antibody, indicating that GM-CSF neutralization does not impair CART cell activity in vivo. This anti-tumor activity was validated in an ALL patient derived xenograft model. Next, we explored the impact of GM-CSF neutralization on CART cell related toxicities in a novel patient derived xenograft model. Here, NOD-SCID-g-/- mice were engrafted with leukemic blasts (1-3x106 cells) derived from patients with high risk ALL. Mice were then treated with high doses of CART19 cells (2-5x106 intravenously). Five days after CART19 treatment, mice began to develop progressive motor weakness, hunched bodies, and weight loss that correlated with massive elevation of circulating human cytokine levels. Magnetic Resonance Imaging (MRI) of the brain during this syndrome showed diffuse enhancement and edema, associated with central nervous system (CNS) infiltration of CART cells and murine activated myeloid cells. This is similar to what has been reported in CART19 clinical trials in patients with severe NT. The combination of CART19, lenzilumab (to neutralize human GM-CSF) and murine GM-CSF blocking antibody (to neutralize mouse GM-CSF) resulted in prevention of weight loss (Fig 1B), decrease in critical myeloid cytokines (Fig 1C-D), reduction of cerebral edema (Fig 1E), enhanced leukemic disease control in the brain (Fig 1F), and reduction in brain macrophages (Fig 1G). Finally, we hypothesized that disrupting GM-CSF through CRISPR/Cas9 gene editing during the process of CART cell manufacturing would result in functional CART cells with reduced secretion of GM-CSF. We designed guide RNA targeting exon 3 of the GM-CSF gene and generated GM-CSFk/o CART19 cells. Our preliminary data suggest that these CARTs produce significantly less GM-CSF upon activation but continue to exhibit similar production of other cytokines and exhibit normal effector functions in vitro (Fig 1H). Using the NALM6 high tumor burden relapse xenograft model as described above, GM-CSFk/o CART19 cells resulted in slightly enhanced disease control compared to CART19 cells (Fig 1I). Thus, modulating myeloid cell behavior through GM-CSF blockade can help control CART mediated toxicities and may reduce their immunosuppressive features to improve leukemic control. These studies illuminate a novel approach to abrogate NT and CRS through GM-CSF neutralization that also potentially enhances CART cell functions. Based on these results, we have designed a phase II clinical trial using lenzilumab as a modality to prevent CART related toxicities in patients with diffuse large B cell lymphoma. Disclosures Ahmed: Humanigen: Employment. Sahmoud:Humanigen: Employment. Durrant:Humanigen: Employment. Russell:Vyriad: Equity Ownership. Kay:Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolero Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees; Cytomx Therapeutics: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Infinity Pharm: Membership on an entity's Board of Directors or advisory committees; Acerta: Research Funding. Kenderian:Novartis: Patents & Royalties; Tolero Pharmaceuticals: Research Funding; Humanigen: Research Funding.

Despite unprecedented successes with immune checkpoint blockade in advanced cancers, these agents provide durable clinical benefit in only a subset of patients. In addition, the clinical management of patients receiving immune checkpoint blockade remains quite challenging due to the unpredictable and kinetically heterogeneous responses which can manifest as late responses, pseudoprogression, or hyperprogression in subsets of patients. The dynamics and heterogeneity of programmed cell death protein ligand 1 (PD-L1, aka B7-H1) expression confound its use as a predictive biomarker in cancer immunotherapy, but blood-based biomarkers have the potential to predict responders and detect mechanisms of resistance to immunotherapy. We previously reported that Bim (BH3-only protein) is a downstream signaling molecule of the PD-1 pathway, and that Bim levels in circulating tumor-reactive T-cells reflected patient responses to anti-PD-1 therapy in melanoma. We also discovered the existence of soluble PD-L1 (sPD-L1) in the plasma of cancer patients and showed a correlation of sPD-L1 with cancer stages in renal cell carcinoma and with prognosis in metastatic melanoma. Here we evaluated the frequency of tumor-reactive T cells with Bim expression along with effector memory profile and sPD-L1 as biomarkers of response in a new cohort of patients with metastatic melanoma and lung cancer undergoing anti-PD-1 therapy. We recruited 100 cancer patients treated with anti-PD-1 therapy who had peripheral blood collected at baseline and at each subsequent radiographic tumor evaluation. Frequencies of Bim+ and effector memory CD8+ T cells were measured by flow cytometry in gated tumor-reactive CD11a high PD1+ CD8+ T cells. We also measured levels of sPD-L1 in plasma at baseline and serially during treatment with ELISA. Baseline T cell markers and sPD-L1 levels and their percent changes in patients who had a radiographic response were compared to those who had progressive disease (PD). We found that patients with objective response after 4 cycles of anti-PD-1 therapy had higher frequency of Bim+ CD8+ T cells at baseline compared to patients with PD (mean 43% vs. 30%, P=0.0484). The frequencies of Bim+ T cells decreased significantly after the first 3 months of treatment in responders compared with progressors (mean -16% vs. + 40% P=0.0111). The frequency of effector memory CD8+ T cells also dramatically increased in responders in 3-6 months after anti-PD-1 therapy (mean 89% vs. 9.56%, p=0.002). High baseline sPD-L1 was associated with progression on anti-PD-1 therapy (mean 2.8 ng/mL vs. 0.7 ng/mL, p=0.07) or development of immune-related toxicities and the levels increased by 12 weeks in patients progressing on therapy. Conclusion: Measurements of T cell biomarkers (Bim and effector memory) and sPD-L1 levels provide a new noninvasive way to predict and monitor patient responses to anti-PD-1 monotherapy in melanoma and lung cancers. Note: This abstract was not presented at the conference. Citation Format: Roxana S. Dronca, Aaron Mansfield, Xin Liu, Susan Harrington, Elizabeth Enninga, Svetomir Markovic, Lisa Kottschade, Rob Mcwilliams, Matthew Block, Wendy Nevala, Michael Thompson, Haidong Dong. Blood-based T cell biomarkers and soluble PD-L1 predict responses and immune-related toxicity to PD-1 blockade in melanoma and lung cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A38.

Malignant pleural mesothelioma is a disease primarily associated with exposure to the carcinogen asbestos. Consistent with this carcinogenic exposure, cytogenetic analyses have identified multiple recurrent structural chromosomal abnormalities in this malignancy, but more recent high-throughput sequencing evaluations of point mutations suggest that there is a low mutational burden in mesothelioma. Since tumor mutational burden has been correlated with responses to treatment with immune checkpoint inhibitors such as nivolumab, it was not consistent that patients with mesothelioma and low mutation burdens would have similar response rates in clinical trials with immune checkpoint inhibitors as patients with non-small cell lung cancer which is associated with a high mutation burden. In order to reconcile these differences, and given the potential for an improved understanding of the molecular pathogenesis of mesothelioma to improve therapeutic options, we used mate-pair sequencing (MPseq) and RNA sequencing (RNAseq) to understand how structural variants affect the transcriptome. MPseq differs from standard next generation sequencing approaches by tiling the whole genome with larger fragments (2-5kb) to reliably detect structural variants such as insertions, deletions and rearrangements. Amongst 22 mesothelioma specimens there were 1535 chromosomal rearrangements (median 41, range 3-298 per specimen), that resulted in junctions or novel fusions of non-coding DNA or genes. Six-hundred thirty-seven of these rearrangements (median 22, range 5-103 range per specimen) resulted in novel fusions of genes. Many of these inter- or intra-chromosomal rearrangements were consistent with a pattern of chromoanagesis such as chromoplexy or chromothripsis. Chromosomal rearrangements detected by MPseq were used to guide analysis of RNAseq data and revealed that these chromosomal junctions resulted in the expression of 179 novel amino acid sequences (median 5, 0-51 range per specimen). To determine whether transcription of chromosomal rearrangement-related junctions have neoantigenic potential, we used in silico tools to determine whether any of the expressed junctions contained peptides that could be presented by patient-specific HLA molecules. The top candidate rearrangement-related peptides with neoantigenic potential bound patient-specific HLA molecules nearly as well or as well as a positive control in competitive binding assays. Our findings represent the discovery of potential neoantigen expression driven by structural chromosomal rearrangements. These results may have implications for the development of novel therapeutic strategies, the selection of patients to receive immunotherapy, and blood-based treatment monitoring strategies. Citation Format: Aaron S. Mansfield, Tobias Peikert, James B. Smadbeck, Julia B. Udell, Farhad Kosari, Stephen J. Murphy, Hongzheng Ren, Vishnu V. Serla, Janet L. Schaefer Klein, Giannoula Karagouga, Faye R. Harris, Carlos Sosa, Sarah H. Johnson, Wendy Nevala, Svetomir N. Markovic, Aaron O. Bungum, Eric S. Edell, Haidong Dong, John C. Cheville, Marie Christine Aubry, Jin Jen, George Vasmatzis. Rearrangement-related peptides with neoantigenic potential in malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5726.

Early testing of aerosolized sargramostim therapy demonstrated anecdotal clinical responses in patients with metastatic melanoma associated with emergence of systemic antitumor immunity. To improve the clinical and immunologic efficacy of therapy without compromising patient safety, we performed a further dose escalation trial in patients with metastatic melanoma.We conducted a dose-escalation clinical trial of HLA-A2 patients with metastatic melanoma to the lung treated with aerosolized granulocyte macrophage colony stimulating factor (GM-CSF) (500-2000 microg/dose, with increments of 250 microg/dose/cohort) twice/d on days 1 to 7 and 15 to 21 every 28 days until progression or severe toxicity to find a dose where a majority of patients develop antitumor immunity. Five patients were treated per each dose level. Clinical, immune, and safety parameters were examined.The study accrued 40 patients. Toxicity was acceptable. All doses levels were exhausted without identifying a dose of GM-CSF at which a majority of patients (or =3 of 5) demonstrated significant up-regulation of antitumor immunity. Three of 16 patients who were tetramer positive for at least one melanoma antigen (eg, MART-1) pretreatment developed an immune response (IR) to different tumor antigens. Two of 9 patients who were tetramer negative to all melanoma antigens pretreatment developed an IR against gp100. The greatest changes in antitumor immunity occurred at the highest dose levels.A dose of aerosolized GM-CSF capable of inducing antitumor immunity in the majority of patients was not reached. All tested doses were well tolerated. The greatest increase in antitumor T cell IRs was achieved at the highest doses of GM-CSF.

Thrombospondins are natural inhibitors of angiogenesis, tumor metastases, and tumor growth (melanoma). ABT-510 is a synthetic analog of thrombospondin-1, well tolerated in phase I studies. We conducted a phase II trial evaluating the clinical efficacy of ABT-510 and its effects on biomarkers of angiogenesis and immunity in patients with metastatic melanoma (MM).A 2-stage phase II clinical trial was conducted to assess the clinical efficacy, safety, and pharmacodynamic effects (angiogenesis and immunity) of ABT-510 in patients with stage IV melanoma. The primary endpoint was 18-week treatment failure rate. Patients self-administered 100 mg of ABT-510 subcutaneously twice daily. Blood samples were collected at baseline and every 3 weeks while on therapy. Eligible patients demonstrated measurable disease, good performance status and no evidence of intracranial metastases. Correlative laboratory studies evaluated biomarkers of angiogenesis and immunity.Twenty-one patients were enrolled. Most patients were stage M1c (71%) and all had prior therapy for MM. Only 3 of the first 20 patients enrolled were progression free and on treatment at 18 weeks resulting in early termination of the study. Decreases in peripheral blood VEGF-A levels and VEGF-C levels, and CD146 and CD34/133 counts relative to pretreatment were detected. Limited changes in antitumor T cell immunity were observed.ABT-510 therapy administered at 100 mg twice/day in patients with MM did not demonstrate definite clinical efficacy. Further dose escalation or combination with cytotoxic therapy may be more effective therapeutically.

Antibody-directed chemotherapy (ADC) offers an advantage over conventional chemotherapy because it provides antibody-directed targeting, with resultant improvement in therapeutic efficacy and reduced toxicity. Despite extensive research, with notable exceptions, broad clinical application of ADC remains elusive; major hurdles include the instability of antibody–chemotherapy linkers and reduced tumor toxicity of the chemotherapy when bound to the antibody. To address these challenges, we have developed a platform technology that utilizes the nab-paclitaxel formulation of paclitaxel, Abraxane, in which hydrophobic paclitaxel is suspended in 130-nm albumin nanoparticles and thus made water-soluble. We have developed a method to noncovalently coat the Abraxane nanoparticle with recombinant mAbs (anti-VEGF, bevacizumab) and guide Abraxane delivery into tumors in a preclinical model of human A375 melanoma. Here, we define the binding characteristics of bevacizumab and Abraxane, demonstrate that the chemotherapy agent retains its cytotoxic effect, while the antibody maintains the ability to bind its ligand when the two are present in a single nanoparticle (AB160), and show that the nanoparticle yields improved antitumor efficacy in a preclinical human melanoma xenograft model. Further data suggest that numerous therapeutic monoclonal IgG1 antibodies may be utilized in this platform, which has implications for many solid and hematologic malignancies. Cancer Res; 76(13); 3954–64. ©2016 AACR.

Melanoma has a propensity for lymphatogenous metastasis. Improved understanding of the sentinel lymph node (SLN) immunological environment may improve outcomes. The immune phenotype of fresh melanoma SLNs (n = 13) were compared to fresh control lymph nodes (n = 13) using flow cytometry. RNA was isolated from CD4+ T cells of the SLN and control lymph node and assessed for Th1/Th2 gene expression pathways using qRT-PCR. In addition, VEGF expression was compared between primary melanoma (n = 6) and benign nevi (n = 6) using immunohistochemistry. Melanoma SLNs had fewer CD8+ T cells compared to controls (9.2% vs. 19.5%, p = 0.0005). The CD8+ T cells within the SLN appeared to have an exhausted phenotype demonstrated by increased PD-1 mRNA expression (2.2% vs. 0.8%, p = 0.004) and a five-fold increase in CTLA-4 mRNA expression. The SLN also contained an increased number of CD14 (22.7% vs. 7.7%, p = 0.009) and CD68 (9.3% vs. 2.7%, p = 0.001) macrophages, and CD20 B cells (31.1% vs. 20.7%, p = 0.008), suggesting chronic inflammation. RT-PCR demonstrated a significant Th2 bias within the SLN. In vitro studies demonstrated a similar Th2 polarization with VEGF treatment of control lymph nodes. The primary melanoma demonstrated strong VEGF expression and an increase in VEGFR1 within the SLN. Melanoma is associated with Th2-mediated “chronic inflammation,” fewer cytotoxic T cells, and an exhausted T cell phenotype within the SLN combined with VEGF overproduction by the primary melanoma. These immunologic changes precede nodal metastasis and suggests consideration of VEGF inhibitors in future immunotherapy studies.

Lessons Learned Percutaneous thermal ablation combined with in situ granulocyte-macrophage colony-stimulating factor cytokine therapy was technically feasible and well tolerated. No significant clinical or immunologic responses were seen. Background Melanoma tumor-derived heat-shock proteins (HSPs) and HSP-peptide complexes can elicit protective antitumor responses. The granulocyte-macrophage colony-stimulating factor (GM-CSF) chemokine can also promote uptake and processing by professional antigen presenting cells (APCs). On this basis, we designed a pilot study of percutaneous thermal ablation as a means to induce heat-shock protein vaccination plus GM-CSF to determine safety and preliminary antitumor activity of this combination. Materials and Methods This study was designed to assess overall safety of percutaneous ablation combined with GM-CSF for unresectable, metastatic melanoma including uveal and mucosal types. All patients received heat-shock therapy (42°C for 30 minutes), then received one of three treatments: (a) intralesional GM-CSF (500 mcg standard dose); (b) radiofrequency ablation (RFA) + GM-CSF; or (c) cryoablation plus GM-CSF. The primary endpoint of the study was the induction of endogenous HSP70 and melanoma-specific cytotoxic T lymphocytes (CTL). Results Nine patients (three per study arm) were enrolled. No dose-limiting toxicity was observed as specified per protocol. All patients developed progressive disease and went on to receive alternative therapy. Median overall survival (OS) was 8.2 months (95% confidence interval [CI] 2–17.2). The study was not powered to detect a difference in clinical outcome among treatment groups. Conclusion Percutaneous thermal ablation plus GM-CSF was well tolerated, technically feasible, and demonstrated an acceptable adverse event profile comparable to conventional RFA and cryoablation. While HSP70 was induced following therapy, the degree of HSP70 elevation was not associated with clinical outcome or induced CTL responses. While percutaneous thermal ablation plus GM-CSF combinations including checkpoint inhibitors could be considered in future studies, the use of GM-CSF remains experimental and for use in the context of clinical trials.

e21054 Background: Up to 50% of patients undergoing resection for advanced melanoma experience recurrence. Identification of preoperative prognostic biomarkers is needed to ascertain risk of relapse and guide postoperative management. Lactate dehydrogenase (LDH) represents a strong prognostic factor in unresectable metastatic (stage IV) melanoma, but its relevance in patients with resected stage III or IV disease remains unknown. Methods: We retrospectively analyzed data from patients with stage III and IV melanoma who had undergone complete resection of disease and received follow-up treatment at Mayo Clinic, Rochester between January 1, 2000 and January 31, 2012. Clinical data were collected from electronic records. Survival data were estimated using the Kaplan-Meier method. Associations of preoperative LDH with time to relapse and death were evaluated using Cox proportional hazards regression models and summarized with hazard ratios and 95% confidence intervals. Results: A total of 154 subjects with resectable stage III or IV melanoma were included in the study. Median age at the time of resection was 58; 54 (35.1%) were female. One-hundred sixteen (75.3%) patients were classified as stage III and 38 (24.7%) stage IV. Adjuvant systemic treatment was administered in 75 (48.7%) patients and adjuvant radiation in 32 (20.7%). Median duration of follow-up was 4.0 years. Sixteen (10.3%) patients had preoperative LDH above the upper limit of normal. Each 50-unit increase in LDH was associated with a 15% increased risk of relapse (HR 1.15; p = 0.040) and 23% increased risk of death (HR 1.23; p = 0.001). After adjusting for age, gender, stage, number of sites, adjuvant systemic treatment, and adjuvant radiation, preoperative LDH remained associated with time to death (HR 1.25; p = 0.002). Preoperative LDH greater than the upper limit of normal was associated with increased hazard of death, both with univariate (HR 2.44; p = 0.005) and multivariate (HR 2.17; p = 0.017) analyses. Conclusions: This study supports the role of elevated preoperative LDH as a predictor of inferior outcomes in patients with advanced melanoma. Further study to correlate LDH to outcomes in the era of adjuvant immunotherapy is required.

3034 Background: Unique to modern immune therapy for cancer is that early in the course of treatment, patients frequently exhibit transient tumor enlargement (pseudo-progression, pPROG) due to tumor infiltration by lymphocytes (TIL). Currently, pPROG cannot be reliably distinguished from true tumor progression (PROG). There is a need for biomarker techniques to discriminate pPROG (effect of therapy) and PROG (therapy failure). Nuclear medicine offers radiopharmaceuticals capable of imaging immune cells; images can be fused to evaluate functional and anatomic characteristics of tumors, and potentially discriminate pPROG from PROG. Methods: In our study of metastatic melanoma patients, SPECT/CT imaging with 99mTc-interleukin-2 (99mTc-IL2) was performed to visualize TIL. Images were collected before/after 12 weeks of ipilimumab (IPI) or pembrolizomab (PEMBRO) therapy. The 99mTc-IL2 tracer was synthesized by conjugating succinimidyl-6-hydrazinopyridine-3-carboxylate (HYNIC-NHS) with commercial interleukin-2 (Aldesleukin). HYNIC-IL2 was incubated with tricine, 99mTcO4- (370-740 MBq) and SnCl2. After labelling 99mTc-IL2 was purified by reverse-phase chromatography and diluted in 5% glucose with 0.1% human albumin before injection. Five patients were enrolled in this study. Two patients failed to complete the 12 week 99mTc-IL2 scan due to discontinuation of IPI after: 1) grade 3 colitis and 2) patient refusal for adverse events attributed to IPI. No adverse events attributable to the tracer infusion were reported. Results: Metastatic lesions could be visualized by the tracer. Some lesions decreased in size, while others increased. A positive correlation was found between size and 99mTc-IL2 uptake, before and after therapy, suggesting the potential discrimination of tumor PROG (no 99mTc-IL2 uptake) from pPROG (high 99mTc-IL2 uptake). Immunohistochemical staining for TIL of 99mTc-IL2 positive and negative lesions are illustrated. Conclusions: The results demonstrate feasibility of 99mTc-IL2 imaging as a clinically useful tool capable of discriminating tumor PROG from pPROG. A clinical validation study is in progress. Clinical trial information: NCT01789827.

11534 Background: To date, there are no validated blood-based biomarkers of predicting response to PD-1 blockade. We previously reported that Bim is a downstream signaling molecule of the PD-1 pathway, and that measurement of Bim levels in circulating T-cells may predict and monitor responses to anti–PD-1 therapy in melanoma. We have identified the existence of sPD-L1 in cancer patients and showed that the sPD-L1 is biologically active and capable of triggering apoptosis in activated T-cells. Here we evaluated T cell Bim and sPD-L1 in the peripheral blood (PB) as biomarkers of response in a cohort of patients with metastatic melanoma and lung cancer undergoing anti-PD1 therapy. Methods: 60 pts treated with anti-PD-1 had PB collected at baseline and at radiographic tumor evaluation. Frequencies of Bim+ T cells and Bim median fluorescence intensity (MFI) were measured by flow cytometry in gated tumor-reactive CD11ahighPD1+ CD8+ T cells. We also measured levels of sPD-L1 at baseline and serially during treatment with sPD-L1 ELISA. Baseline Bim and sPD-L1 levels and percent change in Bim levels in patients (pts) who had a radiographic response (CR/PR) were compared to those who had progressive disease (PD) at 12 wks. Results: Similarly to previously reported preliminary data, pts with objective response (CR/PR, 15/60) after 4 cycles of anti-PD1 therapy had higher frequency of Bim T cells at baseline compared to pts with PD (16/60) (mean 43% vs. 30%, P = 0.0484). The frequencies of Bim+ T cells decreased significantly after the first 3 months of treatment in responders compared with progressors (mean -16% vs. + 40% P = 0.0111). High baseline sPD-L1 were associated with progression on anti-PD1 therapy (mean 2.8 ng/mL vs. 0.7 ng/mL, p = 0.07, n = 13) and the levels increased by the first tumor assessment in patients resistant to anti-PD-1. Conclusions: Measurements of Bim and sPD-L1 levels may help to select patients who are likely to benefit from anti-PD1 monotherapy versus combinatorial strategies, and provide a new non-invasive way to monitor response to anti-PD-1 blockade. A larger validation study is underway.

4 Background: Membrane expression of PD-L1 on tumor cells is associated with poor survival in patients with advanced malignancies including metastatic melanoma (MM). In addition, tumor-associated PD-L1 has been proposed as a predictor of response to anti-PD-1 therapy, although responses are observed in some cases of PD-L1 negative MM. We hypothesize that tumor-derived PD-L1 has additional systemic effects through the release of biologically active soluble forms of PD-L1 (sPD-L1) into the circulation, which further impedes the anti-tumor immune response and contributes to poor clinical outcomes in MM. Methods: We developed a sPD-L1 ELISA and biochemically confirmed the identity of the detected protein. We measured the levels of sPD-L1 in 276 patients with MM enrolled on 3 clinical trials who had stored pre-treatment plasma samples and 37 healthy volunteers (HV) undergoing blood donation at Mayo Clinic. We also measured sPD-L1 in baseline samples from 38 MM patients treated with anti-PD1 (pembrolizumab) 2 mg/kg every 3 weeks. ROC analysis was used to compute sPD-L1 concentration cut-off value and Wald test was used to asses the difference of overall survival (OS) in patients with low versus high sPD-L1 concentration. Results: We found that sPD-L1 levels were significantly elevated in MM patients compared with HV (p=0.0011). Mean sPD-L1 level in MM was 1.73 ng/mL (range: 0.13-18.29) compared with 0.77 ng/mL (range: 0.11–6.02) for HV. Patients with higher levels (>0.293 ng/mL) had a median OS of 11.3 months compared to 14.8 months for patients with sPD-L1 level ≤ 0.293 ng/mL (p=0.040). Similarly to tumor-related PD-L1 findings, patients who had clinical benefit (OR/PR/SD) after 4 cycles of anti-PD1 had higher sPD-L1 levels at baseline (2.1 vs. 1.1 ng/mL). Conclusions: To our knowledge, our study is the first to report a correlation of sPD-L1 with MM patient outcome, although a larger study is needed to establish the utility of sPD-L1 as an independent prognostic and possibly predictive biomarker.

There is ample evidence that immune-related processes in humans are under temporal regulation. The circadian variation of humoral and cellular immunity is well documented and appears to be hormonally modulated via the hypothalamic–pituitary–adrenal axis. In advanced melanoma, it has recently been demonstrated that systemic immunity is repolarized toward a global state of chronic inflammation (Th2 dominance) and appears to be governed by infradian biorhythms of cytokines and immune cell subsets, which extend beyond the 24-h circadian variability reported in healthy volunteers. It is suggested that synchronizing administration of lymphodepleting chemotherapy (temozolomide) with these endogenous (individualized) immune dynamics (biorhythms) in patients with advanced/metastatic melanoma improves clinical outcomes compared with temozolomide used in a conventional ‘random delivery’ fashion.

Purpose: Immunotherapeutic modalities are commonly used for treatment of patients with melanoma. The therapeutic success in preclinical models has not yielded the expected clinical results. To understand this discrepancy, we attempted to define immune homeostasis of 209 patients with melanoma across stages of disease relative to normal controls.Experimental Design: Peripheral blood mononuclear cells (PBMC) and plasma were collected from patients and healthy donors. PBMC were analyzed for frequencies of natural killer, dendritic, and T cells and their functional status. Matched plasma samples were analyzed for the concentrations of 27 cytokines, chemokines, and growth factors. RNA was isolated from 24 metastatic melanoma tumor biopsies and profiled by microarray analysis.Results: The frequency of natural killer, T, and dendritic cells in patients does not significantly change across stages of melanoma. However, plasma concentrations of Th2 cytokines [interleukin (IL)-4, IL-5, IL-10, and IL-13] in tumor-bearing patients were significantly higher than those with resected melanoma. Expression array analysis of metastatic melanoma revealed that the malignant melanocytes were not the source of the Th2 cytokines but did highly up-regulate vascular endothelial growth factor (VEGF) transcripts, consistent with plasma VEGF concentrations. In vitro VEGF exposure of normal PBMC lead to repolarization from Th1 to Th2 emulating the state of metastatic melanoma.Conclusions: Patients with metastatic melanoma exist in a state of Th2-mediated “chronic inflammation” as a result of at least VEGF overproduction by malignant tumors. These data support prior observations regarding the effect of VEGF on immune cell function and suggests consideration of VEGF inhibitors in future cancer immunotherapy clinical studies in metastatic melanoma.

Background: The metastatic advancement of melanoma is largely dependent on its ability to evade immunity and gain access to the lymphatics. Characterization of tumor-draining, sentinel lymph nodes in patients has identified the nodes to express an immunosuppressed, Th2-dominant immune profile. Importantly, this profile is observed in sentinel lymph nodes even prior to evidence of metastasis supporting a model in which melanoma-derived factors prime tumor-draining, sentinel lymph nodes for tumor progression. Recent work in our lab has characterized the cellular interactions and the contribution of soluble factors in facilitating this immunosuppressive immune profile in fresh sentinel lymph nodes of patients; however, an appreciation for the role of subcellular counterparts remains to be explored. In this study, we considered a novel role for melanoma-derived, membrane-bound nanoparticles as drivers in polarizing immunity towards an immunosuppressive, tumor-promoting state. Methods and Results: Utilizing recent technology advances in Nanoparticle Tracking Analysis (NTA), characterization of melanoma derived vesicles from human melanoma cell lines showed a size distribution of particles ranging from 30nm to 1um, representing both exosomes and microvesicles. Following hypoxic culture, vesicle production was amplified, suggesting the increasingly hypoxic tumor microenvironment may trigger vesicle secretion. To evaluate the immune regulating potential of melanoma-derived vesicles, proteomic analysis of vesicle cargo by mass spectrometry identified over 100 proteins including known immune regulators Galectin 3, MHC I, ICAM1 and MIF. Functional assessment revealed that dendritic cells matured in vitro in the presence of melanoma-derived vesicles have significantly reduced surface marker expression of co-stimulatory markers CD80 and CD86 compared to controls. In addition to an activation defect, microarray analysis of dendritic cells matured in the presence of melanoma vesicles displayed a unique RNA expression profile. Pathway analysis of the expression arrays identified numerous overlapping signaling pathways involving proteins present in the melanoma-derived vesicles by mass spectrometry suggesting tumor-derived vesicle cargo has the ability to modulate dendritic cell function. Conclusion: Taken together, this study demonstrates a critical function for melanoma-derived vesicles in driving immunosuppression by characterizing their generation, protein cargo and immune regulating properties. The enrichment of melanoma-derived vesicles for immune mediators and ability of the vesicles to suppress dendritic cell function suggests a mechanism by which regional immunosuppression precedes nodal involvement and may foster an environment for metastasis to occur. Moving forward, we are currently translating these findings into fresh sentinel lymph nodes obtained from patients in order to elucidate the role of melanoma-derived vesicles in metastasis. Understanding this mechanism may yield valuable insight as we seek to develop efficacious immunotherapies targeting nodal metastasis. Citation Format: Rachel Goldenstein, Wendy Nevala, Svetomir N. Markovic. Melanoma-derived nanovesicles as drivers of immunosuppression. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A70.

Introduction: Galectin-9 (Gal-9) is a carbohydrate-binding protein that interacts with T-cell immunoglobulin mucin 3 (TIM3) to modulate immune homeostasis. The Gal-9/TIM3 interaction down regulates activated T cells which promotes tumor growth, much like program death 1 (PD-1) and its ligand (PD-L1). Still, the effect Gal-9 has on the immune environment of melanoma patients is weakly understood. This study focuses on the role of Gal-9 in immunoregulation of healthy persons and metastatic melanoma patients. Methods: Soluble Gal-9 levels were determined from plasma collected from patients and healthy persons using standard ELISA methods. Proliferation and apoptosis of cells in the presence and absence of Gal-9 was determined by mixed lymphocyte reactions and Tunnel staining. Supernatants from these reactions were collected and run using a cytokine bead assay to determine changes in immune parameters with and without Gal-9. Results: Soluble Gal-9 was significantly higher in metastatic melanoma patients compared to healthy controls (3929 vs. 877 pg/mL, p=0.0003 respectively). In the presence of Gal-9, the proliferative effect of an allostimulus could be overridden until the level of responder cells to stimulator cells was 4:1. Using an apoptosis assay, Gal-9 was found to increase the level of cellular apoptosis; however, apoptosis was decreased as the allostimulus increased. Healthy cells incubated with Gal-9 were found to increase secretion of growth factors (EGF and FGF-2), chemokines (CXCL1, CXCL8, CCL2 and CCL3), T helper 1 cytokines (IFN-g and IL-7) which have shown tumor promoting affects and T helper 2 cytokines (IL-13 and IL-4). Conclusions: Gal-9 may potentially play a role in suppressing anti-tumor immunity. This suggests the use of a Gal-9 neutralizing antibody for therapeutic benefit in melanoma. Citation Format: Elizabeth Ann L. Enninga, Wendy K. Nevala, Svetomir N. Markovic. Galectin-9 has tumor promoting properties that may be targetable in metastatic melanoma. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A41.

Background: Phase 3 clinical results demonstrate that nab-paclitaxel (ABX) exhibits single agent activity in patients with metastatic melanoma relative to dacarbazine. Additionally, phase 2 clinical data suggest that ABX combined with bevacizumab (BEV) with/without carboplatin exhibits greater clinical efficacy than ABX alone. We hypothesized that the latter may be due to a pharmacokinetic, non-covalent interaction between bevacizumab (BEV) and nab-paclitaxel (ABX) allowing for greater localization of ABX to sites of VEGF overproduction (metastases). Herein we present pre-clinical data describing the utility of experimentally created ABX/BEV complex nanoparticles used to deliver ABX to VEGF producing cancer targets. Methods and Results: To test whether BEV binds to ABX we employed flow cytometry and discovered that the BEV does bind to ABX while preserving the ability of BEV to bind its ligand, VEGF. To measure binding affinity we used Biolayer Interferometry (BLItz) to measure association and dissociation constants. Results of BLItz experiments demonstrate that the binding affinity of BEV to ABX is pH and temperature dependent. The size and stability of the nanoparticle formed by binding BEV and ABX was determined using light refraction (Mastersizer) and Brownian motion (Nanosight). Results of these experiments suggest that a range of nanoparticles can be produced and stability of the BEV particle is increased relative to ABX particles alone. Finally the tumor efficacy of the BEV/ABX complex relative to ABX and BEV as well as sequential administration of the two drugs was tested in a xenograft model of A375 human melanoma cell line. Pharmacokinetic studies in these mice suggest that more ABX is deposited in the tumor site when treated with the complexes relative to ABX alone. Conclusions: The therapeutic antibody BEV has the capability to bind to the chemotherapy drug ABX while still binding its ligand, VEGF. The resulting nanoparticle is more stable than the original ABX particle. In a preclinical model of human A375 xenografts in nude mice, AB160 treatment offers significantly improved antitumor activity beyond that of ABX, BEV or ABX+BEV with no additional toxicity. Initial results indicate that the improved efficacy of the ABX/BEV nanoparticle relative to ABX alone is primarily due to the ability of the anti-VEGF antibody (BEV) to target the chemotherapy agent to the tumor where local VEGF concentration is very high. Clinical translation of the safety of a 160nm AB particle (AB160) in patients with metastatic melanoma is in progress. Citation Format: Wendy K. Nevala, Svetomir N. Markovic. Targeted nano-immune conjugates to melanoma: Preclinical testing of bevacizumab targeted nab-paclitaxel. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B77.

9013 Background: Given the variability in response to novel immunotherapeutic agents such as anti-PD1/PD-L1 therapies and the desire to extend their long-term benefit to more patients (pts), there is an increased need for the development of biomarkers that can help predict treatment outcomes and ensure that these treatments, which may have significant toxicities, are offered to pts more likely to benefit. We evaluated Bim (BCL-2-interacting mediator of cell death) in peripheral blood (PB) tumor-reactive CD11ahighPD-1+CD8+cytotoxic T lymphocytes (CTL) as a marker of the status of PD-1 engagement and T-cell reversibility to identify pts with MM who are more likely to benefit from anti-PD-1. Methods: MM patients treated with Pembrolizumab (pembro) 2 mg/kg every 3 weeks through an Expanded Access Program (EAP) had PB collected at baseline and at radiographic tumor evaluation through a separate biomarker sub-study. Frequencies of Bim+ T cells and Bim median fluorescence intensity (MFI) were measured by flow cy...

9512 Background: In 2012, 1.5-1.6 million patients received hospice care in United States. The majority received care at home. Unfortunately caregiving has been reported as an independent risk fact...

Therapeutic peptide vaccines for melanoma continue to only demonstrate anecdotal success. We set out to evaluate the impact of low-dose GM-CSF emulsified in Montanide ISA-51 on the immunogenicity of HLA-A2 restricted melanoma differentiation antigen peptide vaccines (MART-1, gp100 and tyrosinase) administered in separate subcutaneous injections.We conducted a randomized phase II clinical trial of HLA-A2+ patients with metastatic melanoma that were immunized every 3 weeks with one of the following vaccine preparations: (A) peptides + Montanide ISA-51; (B) peptides + Montanide ISA-51 + GM-CSF (10 microg); (C) peptides + Montanide ISA-51 + GM-CSF (50 microg). Immunization efficacy was determined by quantification of vaccine specific tetramer positive cytotoxic T cells in peripheral blood. Global assessment of immune competence was ascertained using DTH testing to common recall antigens as well as peripheral blood immunophenotyping.Twenty-five eligible patients were equally distributed across all 3 treatment groups. Only 9 patients demonstrated evidence of immunization. Most commonly, immune response was achieved to the gp100 peptide. The addition of low-dose GM-CSF did not impact immunization efficacy. DTH reactivity to Candida appeared predictive of successful immunization. Successful immunization with the peptide vaccines was associated with improved clinical outcomes.The addition of low dose GM-CSF to peptide vaccines did not enhance immunogenicity. Higher doses of GM-CSF may be needed to achieve this effect and this is a testable hypothesis. Likewise, better patient selection based on immunologic status (DTH reactivity) may be helpful to better understand the clinical impact of therapeutic cancer vaccines.

e20046 Background: The immune system and VEGF may play a role in melanoma behavior. We prospectively collected data in 10 stage III and 22 stage IV melanoma patients to observe factors influencing outcomes. Methods: We assessed median survival (MS), LDH, BRAF, VEGF, Th1/Th2 ratio, regulatory T cells (Tregs) and CD4/CD8 ratio, which were measured upon enrollment. LDH and BRAF were measured in standard commercial labs; VEGF via ELISA at LVHN; Th1/Th2 ratio and CD4/CD8 ratio via flow cytometry at Mayo Clinic. Stage III patients were treated with resection and interferon or observation. Stage IV patients were treated with some or all of the following: resection +/- GM-CSF, IL-2, ipilimumab, vemurafenib, carboplatin/paclitaxel/bevacizumab and temazolamide. Results: MS for stage IV patients was 48 months using a Kaplan-Meier survival curve. The only variable associated with survival was LDH, (HR=1.0017, 95%CI: 1.0003-1.0032, p=0.02). In stage IV patients, there was a positive correlation between VEGF and Tregs (r=.485, n=22 p=0.022) and a negative correlation between Tregs and Th1/Th2 (r=-.470, n=22, p=0.027). In stage III/IV patients who were alive at study completion, there was a positive correlation between CD4/CD8 and VEGF (r=.792, n=10, p=0.006). In patients who died, there was a negative correlation between Tregs and Th1/Th2 (r=-.660, n=12, p=0.02). 7 of the stage IV patients are currently disease free, including 5 of the 10 who received IL-2 +/- metastectomy. Conclusions: While a median survival of 48 months was provocative for stage IV patients, it may reflect referral selection at an IL-2 center. Recent advances such as ipilimumab (which lowers Tregs), BRAF inhibitors, and immunotherapy/aggressive resection as initial therapy may have impacted survival. The literature suggests that an elevated CD4/CD8 ratio predicts better outcomes. Higher VEGF levels have also been associated with lower overall survival in patients treated with IL-2. We found an association between higher VEGF levels and increased Tregs in deceased patients but not in living patients. In patients still alive, higher VEGF was balanced by a higher CD4/CD8 ratio. We did not find a correlation between baseline VEGF and survival.

82 Background: Metastatic malignant melanoma is a nearly uniformly fatal disease. Systemic therapy has notable but limited success. Novel therapeutic strategies are urgently needed. To that end, we’ve pursued combinatorial therapeutics using conventional chemotherapy added to an inhibitor of angiogenesis (bevacizumab) with some evidence of clinical benefit. Preliminary analysis of one of our trials suggested a previously unrecognized immunomodulatory effect of bevacizumab when added to chemotherapy in patients with metastatic melanoma, and this may have a potential impact on clinical outcome. Herein we evaluate the immunomodulatory effect of bevacizumab when added to chemotherapy in patients with metastatic melanoma. Methods: We measured levels of peripheral blood mononuclear cell phenotypes in addition to 42 cytokines, chemokines and growth factors in plasma of 55 patients who received albumin-bound paclitaxel and carboplatin (AC) and of 73 patients who received AC with bevacizumab (ACB) on clinical trials N057e and N0775 respectively. The relative percent change in PBMC cell counts and cytokine levels were determined from baseline at their restaging evaluation after two cycles of therapy. The Mann Whitney U test was used to compare responses between the groups. Results: There was a significant increase in CD197+type 1 macrophages in the group that received ACB (35.3%, -11.8-142.7%) compared to AC (-11.6%, -45.9-38.3%; p=0.004). There was a significant decrease in IL-6 in the group that received ACB (-42.4%, -87.7-0.0%) compared to AC (28.4%, -37.4-480%; p=0.0018). Conclusions: The addition of bevacizumab to chemotherapy for the treatment of metastatic melanoma modulates cellular immunity and a pro-inflammatory cytokine. Patients who received bevacizumab had a significant increase in CD197+ type 1 macrophages and a significant decrease in IL-6. Clinical significance of these findings is the subject of ongoing work.

8599 Background: Chemotherapy resistance is a common, difficult problem for melanoma patients needing long term care and those suffering from recurrence. Neural growth factor receptor (NGFR), also known as CD271, is commonly expressed on mesenchymal stem cells and is important for development, survival and differentiation of cells. This has previously shown to be expressed on melanoma stem cells. We hypothesized that treatment with carboplatin enriches the population of tumor cells for cancer stem cells (CSC) as a mechanism of chemotherapy resistance. Methods: Core tumor samples from 118 patients with metastatic melanoma were obtained from formalin-fixed paraffin embedded specimens. Slides were stained using an anti-CD271 antibody for IHC. A375 melanoma cells were treated with increasing concentrations of carboplatin for approximately 1 year. WT, 6 mg/mL and 10 mg/mL resistant cells were tagged with CD271-PE antibody and run on a flow cytometer. These cells were then tested for gene expression by microarray using an Affymetrix human 133 plus 2.0 chip, and analyzed on Partek software. Pathway analysis of these carboplatin resistant cells was preformed using Ingenuity. Results: Virtually all melanoma tumor samples stained positively for CD271 by IHC, with a median of 50% cells within tumor samples expressing the cytoplasmic marker. Flow cytometry demonstrated an increase in the percentage of cells expressing CD271 as resistance to carboplatin increased. Wild type A375 cells contained 30% positive CD271, A375 6mg/mL resistant contained 42% positive and A375 10mg/mL resistant showed 66% positive. Microarray also exhibited a direct correlation between CD271 gene expression with increasing carboplatin resistance. Functional ontology enrichment revealed development and regulation of the EMT pathway as an important process impacted by our resistant cell line. Conclusions: The data suggests that as melanoma cells become resistant to certain chemotherapy drugs they essentially loose their differentiated phenotype and become more stem cell-like. Monitoring melanoma expression of CD271 could help individualize therapy and anticipate chemotherapeutic resistance in this high-risk group of patients.

e21112 Background: Metastatic malignant melanoma is difficult to treat and has a poor prognosis. Systemic therapy for metastatic melanoma has had limited success and novel drug combinations need to be tested. To that end, we have combined anti-angiogenic therapy (bevacizumab) with chemotherapy in clinical trials and have shown some clinical efficacy. Vascular endothelial growth factor (VEGF) is increasingly seen as an immunosuppressive factor that hampers dendritic cell maturation and reduces antigen presentation. We have recently shown that tumor-derived VEGF plays a role in Th-2 driven systemic chronic inflammation seen in advanced melanoma patients. Therefore, our data suggest that blocking tumor derived VEGF with the monoclonal antibody bevacizumab may impact immunity in such a way that augments anti-tumor immunity enhancing clinical efficacy. Methods: In order to understand the immune status in metastatic melanoma patients on chemotherapy (n=55) or chemotherapy plus bevacizumab (n=73), we measured levels of 42 cytokines, chemokines and growth factors in plasma by a mulit-plex bead assay. Matched pairs analysis was performed to determine if the average responses of the measured cytokines were different between the patients that received chemotherapy with bevacizumab or chemotherapy alone. The pre-treatment levels were compared with levels drawn four weeks after the first treatment. Results: There were significant differences in IL-1a, IL-1ra, IL-6, IL-8 and IP-10 between patients treated with chemotherapy alone relative to patients treated with chemotherapy plus bevacizumab. In all cases of patients treated with chemotherapy plus bevacizumab, the levels of these cytokines all decreased relative to pre-treatment samples. In patients treated with chemotherapy alone the levels of these cytokines increased relative to pre-treatment samples. Conclusions: Our data suggest that treating patients with the anti-angiogenic drug bevacizumab may affect the plasma cytokine milieu by reducing the level of many key inflammatory cytokines. Therefore, the use of bevacizumab in combination with chemotherapy may augment host immunity and elicit a more effective anti-tumor immune response.

8593 Background: Heat shock proteins (HSP) can be heat induced and when released into the extracellular environment, act as immunomodulatory molecules attracting antigen-presenting cells to the sit...

TPS175 Background: Heat shock proteins (hsp) are a family of molecules critical for normal cell survival. HSP can be induced at elevated temperatures and when released into the extracellular enviro...