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The pathogenesis of autoimmune thyroid diseases (AITD) is poorly understood and the association between different immune features and the germline variants involved in AITD are yet unclear. We previously observed systemic depletion of IgG core fucosylation and antennary &alpha, 1,2 fucosylation in peripheral blood mononuclear cells in AITD, correlated with anti-thyroid peroxidase antibody (TPOAb) levels. Fucose depletion is known to potentiate strong antibody-mediated NK cell activation and enhanced target antigen-expressing cell killing. In autoimmunity, this may translate to autoantibody-mediated immune cell recruitment and attack of self-antigen expressing normal tissues. Hence, we investigated the crosstalk between immune cell traits, secreted proteins, genetic variants and the glycosylation patterns of serum IgG, in a multi-omic and cross-sectional study of 622 individuals from the TwinsUK cohort, 172 of whom were diagnosed with AITD. We observed associations between two genetic variants (rs505922 and rs687621), AITD status, the secretion of Desmoglein-2 protein, and the profile of two IgG N-glycan traits in AITD, but further studies need to be performed to better understand their crosstalk in AITD. On the other side, enhanced afucosylated IgG was positively associated with activatory CD335- CD314+ CD158b+ NK cell subsets. Increased levels of the apoptosis and inflammation markers Caspase-2 and Interleukin-1&alpha, positively associated with AITD. Two genetic variants associated with AITD, rs1521 and rs3094228, were also associated with altered expression of the thyrocyte-expressed ligands known to recognize the NK cell immunoreceptors CD314 and CD158b. Our analyses reveal a combination of heightened Fc-active IgG antibodies, effector cells, cytokines and apoptotic signals in AITD, and AITD genetic variants associated with altered expression of thyrocyte-expressed ligands to NK cell immunoreceptors. Together, TPOAb responses, dysregulated immune features, germline variants associated with immunoactivity profiles, are consistent with a positive autoreactive antibody-dependent NK cell-mediated immune response likely drawn to the thyroid gland in AITD.

IgE monoclonal antibodies hold great potential for cancer therapy. Preclinical in vivo systems, particularly those in which the antibody recognizes the host species target antigen and binds to cognate Fc receptors, are often the closest approximation to human exposure and represent a key challenge for evaluating the safety of antibody-based therapies. We sought to develop an immunocompetent rat system to assess the safety of a rodent anti-tumor IgE, as a surrogate for the human therapeutic candidate. We generated a rat IgE against the human tumor-associated antigen chondroitin sulfate proteoglycan 4 (CSPG4) and cross-reactive for the rat antigen. We analyzed CSPG4 distribution in normal rat and human tissues and investigated the in vivo safety of the antibody by monitoring clinical signs and molecular biomarkers after systemic administration to immunocompetent rats. Human and rat CSPG4 expression in normal tissues were comparable. Animals receiving antibody exhibited transient mild to moderate adverse events accompanied by mild elevation of serum tryptase, but not of angiotensin II or cytokines implicated in allergic reactions or cytokine storm. In the long term, repeated antibody administration was well tolerated, with no changes in animal body weight, liver and kidney functions or blood cell counts. This model provides preclinical support for the safety profiling of IgE therapeutic antibodies. Due to the comparable antigen tissue distribution in human and rat, this model may also comprise an appropriate tool for proof-of-concept safety evaluations of different treatment approaches targeting CSPG4.

Intratumoral adenosine is a key immunosuppressive factor linked to poor prognosis and reduced efficacy of T cell checkpoint inhibitors. CD73 is an ectoenzyme and key node in the catabolic pathway responsible for sequential hydrolysis of extracellular ATP to adenosine. ATP is released from necrotic and damaged tumor cells; a phenomenon enhanced as consequence of cytotoxic chemotherapy or radiotherapy. A CD73 inhibiting human monoclonal IgG1-TM antibody, Oleclumab, is currently in phase 2 clinical development for treatment of patients with various solid tumors. The combination of CD73 inhibition with chemotherapy and T cell checkpoint inhibition was tested using two murine cancer models, CT26 (colorectal) or MCA205 (fibrosarcoma) implanted subcutaneously in BALB/c mice or C57BL/6 mice, respectively. Tumor bearing mice were treated with combinations of oxaliplatin and 5-fluorouracil and murine surrogate monoclonal antibodies for Oleclumab and Durvalumab (anti-PD-L1). CT26 implanted mice were also treated with the murine surrogate antibodies in the presence and absence of Docetaxel. In an attempt to define contribution of components, comparator groups received monotherapies and other iterations of the combination. Treatment with anti-CD73 and anti-PD-L1 antibodies, concomitantly with chemotherapy, resulted in improved tumor growth inhibition, plus increased proportions of complete tumor regression (P Citation Format: Jim Eyles, Amanda Watkins, Kristina Ilieva, Stef Mullins, Jude Anderton, Elena Galvani, Fabien Garcon, Kelli Ryan, Brajesh P. Kaistha, Andreas Dannhorn, Stephanie Ling, Tim Slidel, Gozde Kar, Alwin Schuller, Zachary A. Cooper, Kris Sachsenmeier, Nadia Luheshi, Rakesh Kumar, Robert W. Wilkinson. Efficacy and pharmacodynamic effect of anti-CD73/PD-L1 monoclonal antibodies in combination with chemotherapy: Observations from mouse tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1584.

Purpose: Highly aggressive triple-negative breast cancers (TNBCs) lack validated therapeutic targets and have high risk of metastatic disease. Folate receptor alpha (FRα) is a central mediator of cell growth regulation that could serve as an important target for cancer therapy. Experimental Design: We evaluated FRα expression in breast cancers by genomic (n = 3,414) and IHC (n = 323) analyses and its association with clinical parameters and outcomes. We measured the functional contributions of FRα in TNBC biology by RNA interference and the antitumor functions of an antibody recognizing FRα (MOv18-IgG1), in vitro, and in human TNBC xenograft models. Results: FRα is overexpressed in significant proportions of aggressive basal like/TNBC tumors, and in postneoadjuvant chemotherapy–residual disease associated with a high risk of relapse. Expression is associated with worse overall survival. TNBCs show dysregulated expression of thymidylate synthase, folate hydrolase 1, and methylenetetrahydrofolate reductase, involved in folate metabolism. RNA interference to deplete FRα decreased Src and ERK signaling and resulted in reduction of cell growth. An anti-FRα antibody (MOv18-IgG1) conjugated with a Src inhibitor significantly restricted TNBC xenograft growth. Moreover, MOv18-IgG1 triggered immune-dependent cancer cell death in vitro by human volunteer and breast cancer patient immune cells, and significantly restricted orthotopic and patient-derived xenograft growth. Conclusions: FRα is overexpressed in high-grade TNBC and postchemotherapy residual tumors. It participates in cancer cell signaling and presents a promising target for therapeutic strategies such as ADCs, or passive immunotherapy priming Fc-mediated antitumor immune cell responses. Clin Cancer Res; 24(20); 5098–111. ©2018 AACR.

The tumor microenvironment (TME) has multiple mechanisms of immune-suppression, one being recruitment of arginase (ARG) expressing myeloid cells. ARG is an enzyme that catalyzes hydrolysis of L-arginine into urea and L-ornithine. L-arginine is a semi-essential amino acid required for optimal function of T cells and natural killer (NK) cells. Arginine depletion in the TME inhibits T cell and NK cell function. Therefore, inhibition of ARG can reverse immune-suppression and optimize anti-tumor immunity. To determine the dependence to arginine, we cultured human T- and NK cells in arginine concentrations ranging from 0 to 150 µM. Both human CD8+ T cells and NK cells showed decreased proliferation with decreased L-arginine concentration, and a complete proliferation arrest in the absence of L-arginine. L-arginine threshold for optimal proliferation was determined to be ~30 µM for CD8+ T cells and ~ 9 µM for NK cells. Furthermore, both CD8+ T cells and NK cells showed decreases in cytotoxic molecules (e.g. granzyme A, granzyme B, perforin) when cultured under reduced arginine conditions. In addition, NK cells showed a decreased ability to kill target cells in low arginine conditions. We next explored whether arginase inhibition could reverse the immune-suppressive environment in vivo. Administration of arginase inhibitor to tumor bearing mice resulted in a dose dependent increase in both plasma (up to 4 fold) and tumor arginine (up to 12 fold) in all models tested including MC38-ova, CT26, and Lewis Lung. In addition, ARG inhibitor showed signs of in vivo immune cell activation including ~doubling of the number of CD8+ T cells, NK cells, and CD103+ dendritic cells in the tumor microenvironment. Combining with anti PD-L1 further increased the number of CD8+ T cells to ~4-fold of control levels. Arginase inhibitor also increased the activation state of CD8 T cell as determined by percent of granzyme, IFNg, and Ki67 positivity. Moreover, ARG inhibitor resulted in an increase of IFNg and TNFa producing CD8+ T cells in tumor draining lymph nodes. Treatment of tumor bearing mice with ARG inhibitor as monotherapy resulted in modest, but consistent, tumor growth inhibition (TGI) of ~30% in multiple syngeneic models (LL, MC38-ova, CT26). Combining ARG inhibitor with anti-PDL1 significantly improved efficacy reaching ~87% TGI in the MCA38-ova model, with 7/10 mice showing tumor regression. In summary, our pre-clinical data demonstrates that an ARG inhibitor in combination with a checkpoint inhibitor can increase plasma and tumor arginine levels and reverse tumor immune-suppression leading to strong immune activation and anti-tumor responses, suggesting arginase inhibitors could provide an opportunity to increase activity of checkpoint inhibitors clinically. Citation Format: Alwin Schuller, Aatman Doshi, Susan Cantin, Michael Secinaro, Yanjun Wang, Laura Prickett, Sharon Tentarelli, Eric Gangl, Horma Ghadially, Kristina Ilieva, Theresa Proia, Scott Mlynarski, Ray Finlay, Wenlin Shao. Inhibition of arginase in combination with anti-PDL1 leads to increased infiltration and activation of CD8+ T cells, NK cells, and CD103+ dendritic cells in mouse syngeneic tumor models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4523.

Background: All antibodies approved for the treatment of cancer are monoclonal IgGs, and no IgE therapy has yet been tested in humans. The biology of IgE, compared with IgG, offers potential for enhanced immune surveillance and superior effector cell potency against tumor cells. IgE antibodies in preclinical cancer models are not associated with allergic toxicity even in immunocompetent animals, and in vivo efficacy compares favorably with equivalent IgGs. Methods: We conducted a first-in-human first-in-class trial of MOv18, a chimeric monoclonal IgE, in patients with solid tumors expressing folate receptor-alpha, the antigen recognized by this antibody. Antigen expression was deemed positive in the presence of >5% membrane staining of any intensity using the mouse clone BN3.2. Intravenous treatment was administered weekly for 6 weeks, then two-weekly. The trial incorporated pre-treatment skin prick testing with MOv18 IgE, and an ex vivo basophil activation test (BAT) using patient whole blood, with the aim of predicting systemic allergic toxicity and excluding patients at potential risk. Safety, efficacy, markers of immune response, and pharmacokinetics have been evaluated in 24 patients to date, at total doses ranging from 0.07 to 3.0mg. Results: Treatment was well tolerated in almost all patients. The most common toxicity was readily manageable urticaria, without systemic symptoms, signs or tryptase elevation. One patient treated at the 0.5mg dose experienced anaphylaxis, with tryptase elevation, despite a negative pre-dose skin prick test. This was the only patient in the trial with baseline circulating basophils that could be activated by ex vivo exposure to MOv18 IgE. This BAT assay was subsequently used to ensure no further patient with reactive basophils was exposed. Maximum tolerated dose has not yet been reached. Dose-dependent increases in Cmax were observed, and plasma concentrations of 70-100ng/mL achieved at the 1.5mg dose are comparable to typical levels of endogenous IgE. No consistent anti-drug antibody response has been detected. Preliminary evidence of anti-tumor activity was seen in a patient with ovarian cancer at a total MOv18 IgE dose of 0.7mg. Shrinkage of peritoneal metastases was accompanied by a tumor marker reduction meeting Gynecologic Cancer InterGroup criteria for response. Conclusions: These results support for the first time the safety of IgE as a treatment for cancer, and provide preliminary evidence for anti-tumor efficacy of this new therapeutic class. The mechanism of cutaneous toxicity is being investigated. Clinical testing of class-switched IgE versions of approved IgG-based therapeutic antibodies is warranted. Citation Format: James Spicer, Bristi Basu, Ana Montes, Udai Banerji, Rebecca Kristeleit, Gareth J. Veal, Christopher Corrigan, Stephen Till, George Nintos, Timothy Brier, Ionut G. Funingana, Joo Ern Ang, Kam Zaki, Annie Griffin, Claire Barton, Paul Jones, Sarah Mellor, Susan Brook, Katie Stoddart, Christopher Selkirk, Simon Carroll, Heike Lentfer, Natalie Woodman, Amy Pope, Giulia Pellizzari, Mano Nakamura, Kristina M. Ilieva, Atousa Khiabany, Chara Stavraka, Hannah Gould, Jitesh Chauhan, Heather Bax, Sarah Pinder, Debra Josephs, Sophia Karagiannis. Phase 1 trial of MOv18, a first-in-class IgE antibody therapy for cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT141.

Basophils are involved in manifestations of hypersensitivity, however, the current understanding of their propensity for activation and their prognostic value in cancer patients remains unclear. As in healthy and atopic individuals, basophil populations were identified in blood from ovarian cancer patients (n = 53) with diverse tumor histologies and treatment histories. Ex vivo basophil activation was measured by CD63 expression using the basophil activation test (BAT). Irrespective of prior treatment, basophils could be activated by stimulation with IgE- (anti-Fc&epsilon, RI and anti-IgE) and non-IgE (fMLP) mediated triggers. Basophil activation was detected by ex vivo exposure to paclitaxel, but not to other anti-cancer therapies, in agreement with a clinical history of systemic hypersensitivity reactions to paclitaxel. Protein and gene expression analyses support the presence of basophils (CCR3, CD123, Fc&epsilon, RI) and activated basophils (CD63, CD203c, tryptase) in ovarian tumors. Greater numbers of circulating basophils, cells with greater capacity for ex vivo stimulation (n = 35), and gene signatures indicating the presence of activated basophils in tumors (n = 439) were each associated with improved survival in ovarian cancer. Circulating basophils in cancer patients respond to IgE- and non-IgE-mediated signals and could help identify hypersensitivity to therapeutic agents. Activated circulating and tumor-infiltrating basophils may be potential biomarkers in oncology.

Selection of single antigen-specific B cells to identify their expressed antibodies is of considerable interest for evaluating human immune responses. Here, we present a method to identify single antibody-expressing cells using antigen-conjugated fluorescent beads. To establish this, we selected Folate Receptor alpha (FRα) as a model antigen and a mouse B cell line, expressing both the soluble and the membrane-bound forms of a human/mouse chimeric antibody (MOv18 IgG1) specific for FRα, as test antibody-expressing cells. Beads were conjugated to FRα using streptavidin/avidin-biotin bridges and used to select single cells expressing the membrane-bound form of anti-FRα. Bead-bound cells were single cell-sorted and processed for single cell RNA retrotranscription and PCR to isolate antibody heavy and light chain variable regions. Variable regions were then cloned and expressed as human IgG1/k antibodies. Like the original clone, engineered antibodies from single cells recognized native FRα. To evaluate whether antigen-coated beads could identify specific antibody-expressing cells in mixed immune cell populations, human peripheral blood mononuclear cells (PBMCs) were spiked with test antibody-expressing cells. Antigen-specific cells could comprise up to 75% of cells selected with antigen-conjugated beads when the frequency of the antigen-positive cells was 1:100 or higher. In PBMC pools, beads conjugated to recombinant antigens FRα and HER2 bound antigen-specific anti-FRα MOv18 and anti-HER2 Trastuzumab antibody-expressing cells, respectively. From melanoma patient-derived B cells selected with melanoma cell line-derived protein-coated fluorescent beads, we generated a monoclonal antibody that recognized melanoma antigen-coated beads. This approach may be further developed to facilitate analysis of B cells and their antibody profiles at the single cell level and to help unravel humoral immune repertoires.

Malignant melanoma is associated with poor clinical prognosis; however, novel molecular and immune therapies are now improving patient outcomes. Almost 50% of melanomas harbor targetable activating mutations of BRAF that promote RAS–RAF–MEK–ERK pathway activation and melanoma proliferation. Recent evidence also indicates that melanomas bearing mutant BRAF may also have altered immune responses, suggesting additional avenues for treatment of this patient group. The small molecule inhibitors selective for mutant BRAF induce significant but short-lived clinical responses in a proportion of patients, but also lead to immune stimulatory bystander events, which then subside with the emergence of resistance to inhibition. Simultaneous BRAF and MEK inhibition, and especially combination of BRAF inhibitors with new immunotherapies such as checkpoint blockade antibodies, may further enhance immune activation, or counteract immunosuppressive signals. Preclinical evaluation and ongoing clinical trials should provide novel insights into the role of immunity in the therapy of BRAF-mutant melanoma. Mol Cancer Ther; 13(12); 2769–83. ©2014 AACR.

The increasing biotechnological interest in human IgE antibodies demands advanced systems which allow their proper expression. However, this is still a challenge due to the complexity of the molecule, particularly regarding the diverse N-glycosylation pattern. Here, we present the expression of recombinant IgE in wild type and glycan-engineered Nicotiana benthamiana plants and in-depth N-glycosylation analyses. Mass spectrometric profiling revealed that plant IgE has a site occupancy rate that ranges from non-occupied at glycosite 6 (GS6) to 100% occupancy at GS1 and 2. Similarly to human cell-derived IgE, plant versions carry complex N-glycans at GS1–5 and oligomannosidic structures at GS7. Computational modelling suggests that spatial position (or orientation) of glycans can impair processing or site occupancy on adjacent glycosites. IgE expressed in glycoengineered and wild type plants carry, respectively, GnGn and plant-typical GnGnXF structures at large homogeneity. This contrasts with the glycan diversity of HEK cell-derived IgE, carrying at least 20 different glycoforms. Importantly, IgE glycoengineering allows the control of its glycosylation, a so far unmet need when using well-established expression systems. This enables the elucidation of possible carbohydrate-dependent IgE functions. Significance Targeted glycosylation of recombinant proteins may provide an advantage in therapeutic applications. Despite increasing biotechnological interest in IgE antibodies, knowledge and impact of glycosylation on this antibody class are scarce. With the ability to glyco-engineer recombinant IgE, we provide an important step towards the generation of IgE with other targeted N-glycans. This will facilitate detailed structure–function studies and may lead to the production of IgE with optimized activities.

IgE antibodies are key mediators of antiparasitic immune responses, but their potential for cancer treatment via antibody-dependent cell-mediated cytotoxicity (ADCC) has been little studied. Recently, tumor antigen–specific IgEs were reported to restrict cancer cell growth by engaging high-affinity Fc receptors on monocytes and macrophages; however, the underlying therapeutic mechanisms were undefined and in vivo proof of concept was limited. Here, an immunocompetent rat model was designed to recapitulate the human IgE-Fcϵ receptor system for cancer studies. We also generated rat IgE and IgG mAbs specific for the folate receptor (FRα), which is expressed widely on human ovarian tumors, along with a syngeneic rat tumor model expressing human FRα. Compared with IgG, anti-FRα IgE reduced lung metastases. This effect was associated with increased intratumoral infiltration by TNFα+ and CD80+ macrophages plus elevated TNFα and the macrophage chemoattractant MCP-1 in lung bronchoalveolar lavage fluid. Increased levels of TNFα and MCP-1 correlated with IgE-mediated tumor cytotoxicity by human monocytes and with longer patient survival in clinical specimens of ovarian cancer. Monocytes responded to IgE but not IgG exposure by upregulating TNFα, which in turn induced MCP-1 production by monocytes and tumor cells to promote a monocyte chemotactic response. Conversely, blocking TNFα receptor signaling abrogated induction of MCP-1, implicating it in the antitumor effects of IgE. Overall, these findings show how antitumor IgE reprograms monocytes and macrophages in the tumor microenvironment, encouraging the clinical use of IgE antibody technology to attack cancer beyond the present exclusive reliance on IgG. Cancer Res; 77(5); 1127–41. ©2017 AACR.

ER stress is activated in a number of important diseases such as diabetes, cancer, and neurodegeneration, but the molecular interactions governing the response are still being elucidated. In the absence of stress, protein complexes exist between the ER-resident chaperone BiP and three transmembrane signalling molecules which are responsible for signal transmission. Previous results suggested that cofactors might participate in these interactions, but the molecular details are not well understood. We coexpressed BiP and the lumenal domains of each of the three ER stress transducers and copurified the complexes in the presence of ATP and ADP in order to better understand how the complex is formed. ATP, but not ADP, was required to isolate the BiP-IRE1 and the BiP-PERK complexes, but the BiP-ATF6 complex was purified in all conditions tested. Based on the results, we hypothesize that in contrast to its mode of binding ATF6 and unfolded proteins, BiP binds to IRE1 and PERK in a different manner.

Antibodies have been detected against known melanoma-associated antigens in patients with malignant disease. While much is known about cancer-specific T cell responses, the nature of cancer-specific B cells and their antibody repertoires are less well understood. We investigated circulating skin-homing B cells (CD19+CD22+CLA+) in healthy volunteers (n = 24) and melanoma patients (n = 49) and examined the presence of CD22+ B cells in melanoma lesions (n = 173) and normal skins tissue (n = 16). We detected mature IgG mRNA in 13 of 27 normal skin and 9 of 21 cutaneous melanoma samples and we detected mRNA for the enzyme Activation-induced cytidine deaminase (AID). IgG variable heavy chain sequences from melanomas (n = 51) and normal skins (n = 29) featured lower IgG1/IgGtotal subclass representation compared with circulating B cell antibody sequences (n = 36). The presence of affinity-matured cutaneous antibody repertoires in malignant skin was supported by evidence of somatic hypermutation, class-switching and B cell clonal family trees in melanoma lesions and a subset of melanoma-associated clones featuring shorter CDR3 region lengths relative to circulating B cell sequences. Homology modelling also indicated differential putative binding site patterns in melanoma compared to normal skin-resident antibodies, suggesting distinct melanoma-associated repertoires and potentially, antigen recognition profiles. These findings support the presence of a mature tumor-resident B cell compartment with characteristics distinct to that of B cells in normal skin and the circulation. Citation Format: Louise Saul, Kristina M. Ilieva, Heather J. Bax, Panagiotis Karagiannis, Isabel Correa, Irene Rodriguez-Hernandez, Debra H. Josephs, Isabella Tosi, Isioma U. Egbuniwe, Sara Lombardi, Silvia Crescioli, Carl Hobbs, Federica Villanova, Anthony Cheung, Jenny LC Geh, Ciaran Healy, Mark Harries, Victoria Sanz-Moreno, David Fear, James F. Spicer, Katie E. Lacy, Frank O. Nestle, Sophia N. Karagiannis. IgG antibody switching and clonal expansion in melanoma and normal skin microenvironments [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A116.

Purpose: Novel findings point to a pathological and immunoregulatory function of IgG4 antibodies and IgG4+ B cells in inflammatory diseases and malignancies. It has been reported that IgG4 antibodies impair humoral responses and restrict activation of immune effector cells in melanoma and cholangiocarcinomas. Thus the biological function of IgG4 may also be accompanied with predictive potential. Experimental Design: We investigated IgG4 as a potential indicator of the risk of disease progression in human sera (n=271: 167 melanoma patients; 104 healthy volunteers) and peripheral blood B cells (n=71: 47 melanoma patients; 24 healthy volunteers). Results: The serum levels of IgG4 (IgG4/IgGtotal) were elevated in melanoma samples and high IgG4 levels correlated negatively with progression-free survival (hazard ratio (HR) 2.01, 95% confidence interval ([CI]) 1.34-3.35; P=0.0016) and overall survival (HR 1.90 95%[CI] 1.17-3.29; P=0.0116). IgG4 was an independently negative prognostic marker for progression-free survival (PFS; HR 2.46, 95%[CI] 1.01-6.02) in patients with stage I-II disease. Moreover in a similar cohort elevation of IgG4+ circulating B cells (CD45+CD22+CD19+CD3-CD14-) (P=0.014) was also negatively prognostic for progression-free survival. The marker LDH, which is already used in clinical practice, is associated with PFS in melanoma, especially in advanced stages. We found that by combining LDH and IgG4 the prognostic value was improved (AUC:0.67; P=0.0002) than either serum indicator alone. In tissues (n=256; 108 cutaneous melanomas; 56 involved lymph nodes; 60 distant metastases; 32 normal skin samples) we found IgG4+ cell infiltrates in 42.6% of melanomas, 21.4% of involved lymph nodes and 30% of metastases. These findings suggest biological involvement of IgG4 in Th2 tumour environments at the metastatic and local levels. Conclusion: Our data are consistent with emerging evidence for immunosuppressive roles for IgG4, further supporting prognostic utility in melanoma and potential to facilitate patient stratification. Citation Format: Panagiotis Karagiannis, Federica Villanova, Debra H. Josephs, Isabel Correa, Mieke Van Hemelrijck, Carl Hobbs, Louise Saul, Isioma U. Egbuniwe, Isabella Tosi, Kristina M. Ilieva, Emma Kent, Eduardo Calonje, Mark Harries, Ian Fentiman, Joyce Taylor-Papadimitriou, Joy Burchel, James F. Spicer, Katie E. Lacy, Frank O. Nestle, Sophia N. Karagiannis. IgG4: a new tool to predict the risk of disease progression in melanoma. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A009.

Background: Folate receptor α is a GPI-anchored cell surface protein that mediates the intracellular transport of folates. It is over-expressed in a number of malignancies, including ovarian carcinoma and mesothelioma and has limited normal tissue expression. More recently it has been found to be over-expressed in breast cancer, and particularly a less favourable prognostic form, known as ‘triple-negative’ breast cancer (TNBC). We examined a therapeutic antibody candidate recognising FRα; which we are preparing for Phase 1 clinical trials for its potential to target human immune effector cells against breast cancer cells. As part of this effort, we endeavoured to identify a breast cancer cell line model in which the ability for this antibody to induce Antibody-dependent Cell-mediated breast tumour cell death could be evaluated in vitro. Methods: Twenty-two breast cancer cell lines were evaluated by flow cytometry for surface expression of FRα using the anti-FRα antibody compared with IGROV1, a well characterised ovarian cancer cell line used as a positive control. We confirmed these findings with mRNA levels for cell lines available from the publically accessible Cancer Cell Line Encyclopaedia (CCLE). The two highest expressing breast cancer cell lines, T47D and CAL51 were then studied in a functional flow cytometric assay which can simultaneously measure antibody-dependent cell-mediated cytotoxicity (ADCC) and phagocytosis (ADCP). The human monocytic U937 cells which express Fc receptors for IgG and IgE antibodies, served as effectors. We compared the capacity of the the anti-FRα antibodies (IgG1 and IgE isotypes) to activate monocytic cells against the FRα-expressing ovarian carcinoma IGROV1 cells, the breast carcinoma T47D and CAL51 cells and the FRα non-expressing breast cancer cell line, HCC1428. Results: There was wide variety in the levels of cell surface expression of FRα; by breast cancer cell lines, expressed as Mean Fluorescent Intensity (>than an isotype control). The highest expressing breast cancer cell lines, T47D and CAL51 had values of 1273 (SEM 13.6) and 1638 (SEM 24.7) respectively in comparison with the non-expressing cell line, HCC1428 with a value of 8 (SEM 0.54). Expression levels in the ovarian cancer cell line, IGROV1 were 16580 (SEM 2534). These values correlated well with mRNA levels from the CCLE database (Spearman's rank, r=0.6011, p=0.0065) which varied from 1x104-1x1011 amongst breast cancer cell lines but were still below those detected with IGROV1 ovarian cancer cells with an mRNA level of 7x1012. We detected no clear evidence of expressing/non-expressing cell lines clustering amongst any known molecular subtype of TNBC. In vitro functional assay assessments of breast carcinoma cell killing in the non-FRα expressing cell line, HCC1428, revealed that neither IgG nor IgE induced breast cancer cell cytotoxicity above that induced by a non-targeting isotype antibody control. In contrast anti-FRα IgG1 and IgE antibodies could induce 20-30% more ADCP and ADCC, respectively, of the FRα+ IGROV1 tumour cells than the isotype control. The breast carcinoma T47D cells, likewise, were killed by ADCP when exposed to anti-FRα IgG, while the anti-FRα IgE antibody induced high levels of ADCC of ~40% above isotype control. Furthermore, treatment of breast carcinoma cells with anti-FRα antibodies induced direct signalling effects that may lead to reduced growth and survival cascades. Conclusions: We have identified two breast cancer cell line models which could be candidates for further in vitro and in vivo assessment of the efficacy and mechanisms of the novel anti-FRα; IgE against breast carcinomas. We have demonstrated similar levels of human immune effector cell-mediated breast cancer cell killing in one of these cell lines, T47D, to a well characterised ovarian cancer cell line, IGROV1, not seen in the FRα; non-expressing cell line, HCC1428. This tumour antigen warrants further characterisation as a potential new immune therapy in TNBC, where immune infiltration is already known to be favourably prognostic. Citation Format: Matthew W. Fittall, Anthony Cheung, Gyula M. Petranyi, Diana Rodriguez-Dominguez, Heather J. Bax, Panagiotis Karagiannis, Kristina M. Ilieva, Andrew Tutt, Sophia N. Karagiannis. Exploring folate receptor α immunotherapy of breast carcinomas: Human monocytic cell-mediated killing triggered by IgG1 and IgE antibodies. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A090.

Breast cancer is a major cause of death in women in the UK and worldwide. It is now widely recognized that many cancers, including breast, elicit immune cell engagement resulting in immune responses directed against over-expressed or aberrantly presented antigens. A greater understanding of these interactions has had significant effects in improving the prognosis in other tumor types e.g. melanoma, but has not been extensively studied in breast cancer. Here we aim to build disease-relevant in vivo models of breast cancer that recapitulate the immune-tumor microenvironment found in patient tumors. Patient-derived xenografts (PDX) are in vivo pre-clinical models derived from transplantation of patient tumor material into severely immunocompromised hosts. These models recapitulate major clinicopathologic features of patient tumors and represent the breadth of diversity in phenotype and genotype found across breast cancer. These PDX models can be studied in order to further our understanding of intrinsic tumor cell biology and response to treatment. However, as these tumor models are maintained in severely immunocompromised hosts, we cannot study the relevant interactions between tumor and immune cells. In order to address this, we have established humanized PDX models. We have developed a humanized triple-negative breast PDX model in NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice. The experimental set-up is based on those successfully used to identify novel antibody-based therapeutic strategies in melanoma (Karagiannis et al 2013). The PDX tumor is established by orthotopic transplantation into the inguinal mammary fat pad. The host is then engrafted with human immune effector cells (peripheral blood lymphocytes (PBL) isolated from healthy volunteers). Following tumor development, host and tumor tissues are processed for flow cytometry and immunohistochemistry (IHC). We observe a ∼40% engraftment of human immune effector cells in host spleens following transplantation and tumor development by flow analysis. We also observe human CD45+ leukocyte populations in the tumor, blood and other organs. Tumor-infiltrated lymphocytes expressed the immune checkpoint phenotype of patient cancers. We are now investigating the subtypes of immune effector cells present our model, whether novel antibody-based therapies can be used to block tumor formation, and how immune checkpoint molecules are modulated. We are currently testing new PDX models for their capacity for humanization by immune effector cells. Our over-arching aim is to determine whether these models can recapitulate immune responses directed against tumor antigens in order to study the mechanisms of action and efficacy of novel therapeutics to treat breast cancer. Humanized pre-clinical PDX models could be a feasible approach to accelerate therapeutic discovery relevant to impacting tumor and immune stromal interaction for patient benefit. Citation Format: Rebecca Marlow, Kristina Ilieva, Erika Francesch, Fernanda Kyle, Panagiotis Karagiannis, Adrian Hayday, Sophia Karagiannis, Andrew Tutt. Patient-derived xenograft models of breast cancer with human immune components. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1459. doi:10.1158/1538-7445.AM2015-1459

Triple negative breast cancers (TNBCs) are characterised by the lack of estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 (HER2) rendering them insensitive to current endocrine and anti-HER2 therapies, therefore novel treatment options are required. Breast cancers have been shown to be immunogenic and patient tumors feature infiltrating immune cells. Since monoclonal antibodies are an important therapeutic modality in the clinical management of many cancers, engineering antibodies against triple negative breast cancer specific antigens that may activate immune effector cells within tumors and in the circulation may lead to tumour clearance and may provide new treatment strategies for this patient group. Here we describe a platform for selection of TNBC-associated antigens, engineering of novel antibodies against these antigens and functional studies to elucidate antibody mechanisms of action and therapeutic potential in vitro and vivo. Our approach involves identification of tumour-associated antigens from patient tumor specimens using a transcriptomics approach and validation and evaluation of biological functions in breast cancer cells using cell culture models. Antibody heavy (VH) and light (VL) sequences are cloned in a dual expression vector system for recombinant expression in HEK293 cells to rapidly produce antibodies with reactivity to specific tumor antigens. The system is optimised for the seamless expression of V genes of any species including human sequences, along with human constant (C) genes of different antibody classes and subclasses. The latter permits the study of different class/subclass antibodies in order to identify those most effective in triggering immune cell activation and tumor clearance. Engineered monoclonal antibodies are subsequently tested for their antigen binding properties and capacity to activate immune effector cells against cancer cells in vitro. The therapeutic potential of selected candidates is evaluated in vivo using xenograft TNBC mouse models engrafted with components of the human immune system using adoptive transfer of healthy volunteer and patient derived peripheral blood cells. Xenograft models featuring human immune components serve to evaluate the therapeutic potential of monoclonal antibodies in the context of their capacity to redirect immune effector functions against cancer cells. Our findings demonstrate a translational pathway designed to facilitate the discovery and evaluation of novel antibody therapeutic options for triple negative breast cancer immunotherapy. Citation Format: Kristina M. Ilieva, Rebecca Marlow, Anthony Cheung, Erika Francesch, Panagiotis Karagiannis, Matthew Fittall, Silvia Crescioli, Andrew Tutt, Sophia Karagiannis. A translational platform to design antibodies targeting triple negative breast cancer-specific antigens for cancer immunotherapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1324. doi:10.1158/1538-7445.AM2015-1324