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Supplementary Data from Retinoblastoma Tumor Suppressor Gene Expression Determines the Response to Sequential Flavopiridol and Doxorubicin Treatment in Small-Cell Lung Carcinoma

Supplementary Data from Carcinoma-Associated Fibroblast–Like Differentiation of Human Mesenchymal Stem Cells

Significance Immunotherapy has revolutionized cancer treatment, yielding unprecedented long-term responses and survival. However, a significant proportion of patients remain refractory, which correlates with the absence of immune-infiltrated (“hot”) tumors. Here, we observed that FDA-approved unadjuvanted seasonal influenza vaccines administered via intratumoral injection not only provide protection against active influenza virus lung infection, but also reduce tumor growth by increasing antitumor CD8+ T cells and decreasing regulatory B cells within the tumor. Ultimately, intratumoral unadjuvanted seasonal influenza vaccine converts immunologically inactive “cold” tumors to “hot,” generates systemic responses, and sensitizes resistant tumors to checkpoint blockade. Repurposing the “flu shot” may increase response rates to immunotherapy, and based on its current FDA approval and safety profile, may be quickly translated for clinical care., Reprogramming the tumor microenvironment to increase immune-mediated responses is currently of intense interest. Patients with immune-infiltrated “hot” tumors demonstrate higher treatment response rates and improved survival. However, only the minority of tumors are hot, and a limited proportion of patients benefit from immunotherapies. Innovative approaches that make tumors hot can have immediate impact particularly if they repurpose drugs with additional cancer-unrelated benefits. The seasonal influenza vaccine is recommended for all persons over 6 mo without prohibitive contraindications, including most cancer patients. Here, we report that unadjuvanted seasonal influenza vaccination via intratumoral, but not intramuscular, injection converts “cold” tumors to hot, generates systemic CD8+ T cell-mediated antitumor immunity, and sensitizes resistant tumors to checkpoint blockade. Importantly, intratumoral vaccination also provides protection against subsequent active influenza virus lung infection. Surprisingly, a squalene-based adjuvanted vaccine maintains intratumoral regulatory B cells and fails to improve antitumor responses, even while protecting against active influenza virus lung infection. Adjuvant removal, B cell depletion, or IL-10 blockade recovers its antitumor effectiveness. Our findings propose that antipathogen vaccines may be utilized for both infection prevention and repurposing as a cancer immunotherapy.

Background: Coxsackievirus A21 (V937) is an RNA oncolytic virus targeting ICAM-1 receptors. Pharmacodynamic effects of oncolytic viruses in the tumor microenvironment (TME), including increased CD8+ T cells and PD-L1 expression, support their use in combination with checkpoint inhibitors. We present updated clinical and correlative data from the multicenter phase 1b CAPRA study (NCT02565992) of V937 + pembro in pts with advanced melanoma. Methods: Eligible pts had metastatic/unresectable stage IIIB-IV melanoma and ≥1 cutaneous/subcutaneous tumor or lymph node amenable to V937 intratumoral injection. Pts received V937 on days 1, 3, 5, and 8; then Q3W for up to 19 injections (maximum dose, 3 × 108 50% TCID50). Pts received IV pembro 2 mg/kg Q3W on day 8, continuing for up to 2 y. Primary endpoints were incidence of AEs, serious AEs (SAEs), and dose-limiting toxicities (DLTs). Secondary endpoints were ORR, duration of response (DOR), PFS, and OS. Biomarkers were an exploratory endpoint. Results: 36 pts were enrolled (mean age, 68.5 y; 75% male; 22% had prior immunotherapy). As of 4 Nov 2019, median (range) time from first dose to data cutoff was 32.0 (10.7−45.3) mo. No DLTs occurred. Grade 3-5 treatment-related AEs occurred in 5 (14%) pts. 3 (8%) pts had treatment-related SAEs (autoimmune encephalitis and septic shock in 1 pt, keratoacanthoma, autoimmune hepatitis); 1 died from septic shock. Efficacy results included ORR of 47% (CR, 22%; PR, 25%; Table 1). In comparing responders vs nonresponders, baseline tumor samples showed no difference in PD-L1 expression and lower CD3+CD8- infiltrate in responders. Conclusions: V937 + pembro had manageable safety and promising efficacy in pts with advanced melanoma. Response was not associated with an inflamed TME at baseline, indicating that V937 may induce an immune responsive TME. The combination is being studied in the neoadjuvant setting in pts with stage III melanoma (KEYMAKER-U02). Table 1.Efficacy OutcomesV937 + Pembro (N = 36)ORR,a % (95% CI)b47 (30-65)- CR22 (10-39)- PR25 (12-42)DOR,c median (range), moNR (1.4+ to 22.0+)PFS,c,d median (95% CI), mo11.9 (3.4-NR)12-mo PFS,c % (95% CI)45 (28-60)OS,c median (95% CI), mo30.9 (20.3-40.5)12-mo OS,c % (95% CI)85 (68-94)+ indicates no PD by the time of last disease assessment. NR, not reached.aBest overall response with confirmation based on investigator assessment per immune-related response criteria; imaging was performed Q6W.bBased on the exact method for binomial data.cKaplan-Meier estimate.dBased on investigator assessment per immune-related response criteria. Citation Format: Ann W. Silk, Steven J. O'Day, Howard L. Kaufman, Jennifer Bryan, Jacqueline T. Norrell, Casey Imbergamo, Daniella Portal, Edwin Zambrano-Acosta, Marisa Palmeri, Seymour Fein, Cai Wu, Leslie Guerreiro, Daniel Medina, Praveen K. Bommareddy, Andrew Zloza, Bernard A. Fox, Carmen Ballesteros-Merino, Darren Shafren, Mark Grose, Joshua A. Vieth, Janice M. Mehnert. Intratumoral oncolytic virus V937 in combination with pembrolizumab (pembro) in patients (pts) with advanced melanoma: Updated results from the phase 1b CAPRA study [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 CT139.

Nuclear factor kappa B (NF-κB) is constitutively expressed in many primary acute myelogenous leukemia (AML) and leukemic stem cell (LSC) samples. Inhibition of nuclear NF-κB ex vivo results in cyto...

Background ONC201 is a small molecule antagonist of DRD2, a G protein-coupled receptor overexpressed in several malignancies, that has prolonged antitumor efficacy and immunomodulatory properties in preclinical models. The first-in-human trial of ONC201 previously established a recommended phase II dose (RP2D) of 625 mg once every three weeks. Here, we report the results of a phase I study that evaluated the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of weekly ONC201. Methods Patients ≥ 18 years old with an advanced solid tumor refractory to standard treatment were enrolled. Dose escalation proceeded with a 3 + 3 design from 375 mg to 625 mg of ONC201. One cycle, also the dose-limiting toxicity (DLT) window, was 21 days. The primary endpoint was to determine the RP2D of weekly ONC201, which was confirmed in an 11-patient dose expansion cohort. Results Twenty patients were enrolled: three at 375 mg and 17 at 625 mg of ONC201. The RP2D was defined as 625 mg with no DLT, treatment discontinuation, or dose modifications due to drug-related toxicity. PK profiles were consistent with every-three-week dosing and similar between the first and fourth dose. Serum prolactin and caspase-cleaved cytokeratin-18 induction were detected, along with intratumoral integrated stress response activation and infiltration of granzyme B+ Natural Killer cells. Induction of immune cytokines and effectors was higher in patients who received ONC201 once weekly versus once every three weeks. Stable disease of > 6 months was observed in several prostate and endometrial cancer patients. Conclusions Weekly, oral ONC201 is well-tolerated and results in enhanced immunostimulatory activity that warrants further investigation. Trial registration NCT02250781 (Oral ONC201 in Treating Patients With Advanced Solid Tumors), NCT02324621 (Continuation of Oral ONC201 in Treating Patients With Advanced Solid Tumors). Electronic supplementary material The online version of this article (10.1186/s40425-019-0599-8) contains supplementary material, which is available to authorized users.

Recent evidence suggests that glutamate signaling plays an important role in cancer. Riluzole is a glutamate release inhibitor and FDA-approved drug for the treatment of amyotrophic lateral sclerosis. It has been investigated as an inhibitor of cancer cell growth and tumorigenesis with the intention of repurposing it for the treatment of cancer. Riluzole is thought to act by indirectly inhibiting glutamate signaling. However, the specific effects of riluzole in breast cancer cells are not well understood. In this study, the anti-cancer effects of riluzole were explored in a panel of breast cancer cell lines in comparison to the metabotropic glutamate receptor 1-specific inhibitor BAY 36-7620. While both drugs inhibited breast cancer cell proliferation, there were distinct functional effects suggesting that riluzole action may be metabotropic glutamate receptor 1-independent. Riluzole induced mitotic arrest independent of oxidative stress while BAY 36-7620 had no measurable effect on mitosis. BAY 36-7620 had a more pronounced and significant effect on DNA damage than riluzole. Riluzole altered cellular metabolism as demonstrated by changes in oxidative phosphorylation and cellular metabolite levels. These results provide a better understanding of the functional action of riluzole in the treatment of breast cancer.

Purpose: Current prostate cancer management calls for identifying novel and more effective therapies. Self-renewing tumor-initiating cells (TICs) hold intrinsic therapy resistance and account for tumor relapse and progression. As BMI-1 regulates stem cell self-renewal, impairing BMI-1 function for TIC-tailored therapies appears to be a promising approach. Experimental Design: We have previously developed a combined immunophenotypic and time-of-adherence assay to identify CD49bhiCD29hiCD44hi cells as human prostate TICs. We utilized this assay with patient-derived prostate cancer cells and xenograft models to characterize the effects of pharmacologic inhibitors of BMI-1. Results: We demonstrate that in cell lines and patient-derived TICs, BMI-1 expression is upregulated and associated with stem cell–like traits. From a screened library, we identified a number of post-transcriptional small molecules that target BMI-1 in prostate TICs. Pharmacologic inhibition of BMI-1 in patient-derived cells significantly decreased colony formation in vitro and attenuated tumor initiation in vivo, thereby functionally diminishing the frequency of TICs, particularly in cells resistant to proliferation- and androgen receptor–directed therapies, without toxic effects on normal tissues. Conclusions: Our data offer a paradigm for targeting TICs and support the development of BMI-1–targeting therapy for a more effective prostate cancer treatment. Clin Cancer Res; 22(24); 6176–91. ©2016 AACR.

Umbilical cord blood (UCB) is a readily available source of hematopoietic stem cells for transplantation. UCB hematopoietic SCT for average- and large-sized patients is often limited by the number of cells available in a single unit. To address this limitation, we performed experiments to determine if adjunctive therapy with third-party human allogeneic cells enhances the engraftment of human UCB in immunodeficient mice. UCB cells with or without sequential infusion of irradiated third-party allogeneic cells were used in transplantation studies of NOD/SCID and NOD/SCID-IL2Rγ null mice. We studied the impact of irradiated allogeneic cells on colony formation in vitro using long-term culture assays also. Our studies demonstrate that short- and long-term UCB engraftment of immunodeficient mice is enhanced by irradiated allogeneic cells. Secondary transplants demonstrate the durability of engraftment. These preclinical studies support the further development of irradiated allogeneic cells as an adjunct to single UCB transplantation when limiting numbers of cells are available.

Purpose: Small-cell lung cancers (SCLC) are defective in many regulatory mechanisms that control cell cycle progression, i.e., functional retinoblastoma protein (pRb). Flavopiridol inhibits proliferation and induces apoptosis in SCLC cell lines. We hypothesized that the sequence flavopiridol followed by doxorubicin would be synergistic in pRb-deficient SCLC cells. Experimental Design: A H69 pRb-deficient SCLC cell line, H865, with functional pRb and H865 pRb small interfering RNA (siRNA) knockdown cells were used for in vitro and in vivo experiments. The in vivo efficiencies of various sequential combinations were tested using nude/nude athymic mice and human SCLC xenograft models. Results: Flavopiridol then doxorubicin sequential treatment was synergistic in the pRB-negative H69 cell line. By knocking down pRb with specific siRNA, H865 clones with complete pRb knockdown became sensitive to flavopiridol and doxorubicin combinations. pRb-deficient SCLC cell lines were highly sensitive to flavopiridol-induced apoptosis. pRb-positive H865 cells arrested in G0-G1 with flavopiridol exposure, whereas doxorubicin and all flavopiridol/doxorubicin combinations caused a G2-M block. In contrast, pRb-negative SCLC cells did not arrest in G0-G1 with flavopiridol exposure. Flavopiridol treatment alone did not have an in vivo antitumor effect, but sequential flavopiridol followed by doxorubicin treatment provided tumor growth control and a survival advantage in Rb-negative xenograft models, compared with the other sequential treatments. Conclusions: Flavopiridol and doxorubicin sequential treatment induces potent in vitro and in vivo synergism in pRb-negative SCLC cells and should be clinically tested in tumors lacking functional pRB.

Objective MicroRNAs (miRNAs) have been implicated in complex vertebrate developmental systems, such as hematopoiesis, and may play an integral role in the development of human cancers. Based on these observations, we investigated the contribution of miRNAs to acute myelogenous leukemia cell lineage-specific differentiation. Materials and Methods To facilitate the identification of miRNAs and their targets relevant to leukemic cell differentiation, changes miRNA expression were analyzed in the human leukemia cell line HL-60, which historically has been utilized to study lineage-specific changes in response to the differentiation agent 12-O-tetradecanoylphorbol-13-acetate (TPA). Results Using this approach, we have identified a panel of TPA-induced miRNAs that are expressed coincident with HL-60 stereotypic morphological changes characteristic of monocytic differentiation. The transferrin receptor 1(TfR-1; CD71), whose surface expression is downregulated during TPA-mediated HL-60 cell differentiation, has been identified as a target of the TPA-induced miRNA miR-320. Cell culture experiments indicate that enforced miR-320 expression can suppress TfR-1 expression and cell proliferation. Conclusion TPA induces the expression of several miRNAs in HL-60 cells, one such miRNA (miR-320) contributes to downregulation of TfR-1 surface expression characteristically seen during HL-60 monocytic differentiation. Moreover, TfR-1–targeting miRNAs, such as miR-320, may have potential as novel therapeutic agents for cancer due to their inhibitory effects on cell proliferation.

Receptor tyrosine kinases-based autocrine loops largely contribute to activate the MAPK and PI3K/AKT pathways in melanoma. However, the molecular mechanisms involved in generating these autocrine loops are still largely unknown. In the present study, we examine the role of the transcription factor RUNX2 in the regulation of receptor tyrosine kinase (RTK) expression in melanoma. We have demonstrated that RUNX2-deficient melanoma cells display a significant decrease in three receptor tyrosine kinases, EGFR, IGF-1R and PDGFRβ. In addition, we found co-expression of RUNX2 and another RTK, AXL, in both melanoma cells and melanoma patient samples. We observed a decrease in phosphoAKT2 (S474) and phosphoAKT (T308) levels when RUNX2 knock down resulted in significant RTK down regulation. Finally, we showed a dramatic up regulation of RUNX2 expression with concomitant up-regulation of EGFR, IGF-1R and AXL in melanoma cells resistant to the BRAF V600E inhibitor PLX4720. Taken together, our results strongly suggest that RUNX2 might be a key player in RTK-based autocrine loops and a mediator of resistance to BRAF V600E inhibitors involving RTK up regulation in melanoma.

Overexpression of extracellular matrix metalloproteinase inducer (EMMPRIN or CD147), a member of the immunoglobulin family and a glycoprotein enriched on the surface of tumor cells, promotes invasion, metastasis, and growth and survival of malignant cells and confers resistance to some chemotherapeutic drugs. However, the molecular mechanisms underlying the actions of EMMPRIN are not fully understood. In this study we sought to determine whether EMMPRIN contributes to the malignant phenotype of breast cancer by inhibiting anoikis, a form of apoptosis induced by loss or alteration of cell-cell or cell-matrix anchorage, and to explore the signaling pathways involved. We found that in the absence of attachment, human breast carcinoma cells expressing high levels of EMMPRIN formed less compact aggregates with larger surface area and less fibronectin matrix assembly, had higher viability, and were resistant to anoikis. Knockdown of EMMPRIN expression by RNA interference (small interfering RNA or short hairpin RNA) sensitized cancer cells to anoikis, as demonstrated by activation of caspase-3, increased DNA fragmentation, and decreased cellular viability. Furthermore, we observed that the accumulation of Bim, a proapoptotic BH3-only protein, was reduced in EMMPRIN-expressing cells and that silencing of EMMPRIN expression elevated Bim protein levels and enhanced cellular sensitivity to anoikis. Treatment of cells with a MEK inhibitor (U0126) or proteasome inhibitor (epoxomicin) also up-regulated Bim accumulation and rendered cells more sensitive to anoikis. These results indicated that expression of EMMPRIN protects cancer cells from anoikis and that this effect is mediated at least in part by a MAP kinase-dependent reduction of Bim. Because anoikis deficiency is a key feature of neoplastic transformation and invasive growth of epithelial cancer cells, our study on the role of EMMPRIN in anoikis resistance and the mechanism involved underscores the potential of EMMPRIN expression as a prognostic marker and novel target for cancer therapy.

Human T cell leukemia virus 1 (HTLV-1) gene expression is regulated by both the viral Tax protein and by cellular transcriptional factors. We have previously shown that immune activation stimuli such as phorbol esters (PMA) and phytohemagglutinin (PHA) cooperate with HTLV-1 Tax expression to enhance HTLV-1 gene expression in infected T cells through increased activity of the HTLV-1 LTR. We now extend these studies to demonstrate roles for the T cell receptor complex, Lck, and Ras molecules in the coactivation of the HTLV-1 LTR by Tax and T cell activation stimuli. We also observe coactivation of Tax-responsive cellular promoter elements containing NF-κB and serum response factor (SRF) binding sites by Tax and T cell activation stimuli. These results suggest a model whereby T cell receptor stimulation and Tax expression coactivate HTLV-1 gene expression and cellular gene expression, enhancing activation of latent HTLV-1 and expression of cellular genes involved in disease pathogenesis.

Background: Coxsackievirus A21 (CVA21) is a novel bio-selected oncolytic, immunotherapeutic agent. Intratumoral (i.t.) CVA21 injection can induce selective tumor-cell infection, immune-cell infiltration, IFN-γ response gene up-regulation, increased PD-L1 expression, tumor cell lysis and systemic anti-tumor immune responses. Preclinical studies in an immune-competent mouse model of melanoma have revealed that combinations of i.t. CVA21 and anti-PD-1 blockade mediate significantly greater antitumor activity compared to use of either agent alone. A clinical trial evaluating combination CVA21 and pembrolizumab in patients with melanoma was initiated and preliminary data on a pre-established futility endpoint are presented here. Materials and Methods: This is a single-arm, multi-institutional open-label phase Ib clinical trial of i.t. CVA21 and i.v. pembrolizumab for treated or untreated unresectable Stage IIIC-IVM1c melanoma. Subjects with injectable disease receive up to 3 x 108 TCID50 CVA21 i.t. on Days 1, 3, 5, 8, and then every 3 weeks for up to 19 injections. Subjects also receive pembrolizumab (2mg/kg) i.v. every 3 weeks starting on Day 8. The primary endpoint is safety/tolerability by incidence of dose-limiting toxicity. Secondary endpoints include best ORR by immune-related response criteria, progression-free survival, overall survival, quality of life, changes in melanoma-specific T cells, PD-L1 expression and Th1/Th2 gene expression profiles. The protocol included a futility analysis after the first 12 patients. Results: To date, 14 subjects have started on protocol therapy. Overall, the adverse events have been low-grade constitutional symptoms related to CVA21 and expected pembrolizumab-related side effects. No DLT’s have been reported. Currently, 11 patients are evaluable for investigator response assessment, not including 2 subjects who have not yet reached their first assessment and 1 subject who left the study early due to an unrelated adverse event. Among the evaluable subjects, the ORR was 73% (8/11). The DCR (CR+PR+SD) is currently 91% (10/11). In subjects with stage IVM1c disease, the ORR and the DCR is 100% (5/5). The study has met its primary statistical futility endpoint of achieving ≥2 confirmed objective responses (CR or PR) in the first 12 patients enrolled. Currently, the median time to response is 1.6 months. One of the 8 responders displayed early pseudo-progression and later developed a partial response. Conclusions: At a pre-specified futility analysis, combination CVA21 and pembrolizumab appears to be well-tolerated. Early tumor monitoring has identified encouraging reductions in a number of injected and non-injected lesions. Based on these initial results, the sample size has now been expanded to enroll up to 50 patients. Combination therapy of CVA21 and pembrolizumab may represent a new approach for the treatment of patients with injectable advanced melanoma. Citation Format: Ann W. Silk, Howard Kaufman, Nashat Gabrail, Janice Mehnert, Jennifer Bryan, Jacqueline Norrell, Daniel Medina, Praveen Bommareddy, Darren Shafren, Mark Grose, Andrew Zloza. Phase 1b study of intratumoral Coxsackievirus A21 (CVA21) and systemic pembrolizumab in advanced melanoma patients: Interim results of the CAPRA clinical trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr CT026. doi:10.1158/1538-7445.AM2017-CT026

e18541 Background: Magnesium plays important roles in cellular processes. Allogeneic hematopoietic stem cell transplantation provides potentially curative therapy to patients with a variety of hematologic malignancies. A common abnormality post transplant is hypomagnesaemia. Recent studies identified magnesium transporter 1 deficiency in association with XMEN syndrome. These patients exhibit low intracellular [Mg++] and low T cell and NK cell NKG2D expression. Therefore, we investigated this potential functional link between magnesium deficiency and immune function in patients post transplant. Methods: A pilot study investigated whether detectable changes in T and NK cells were associated with IV magnesium repletion post hematopoietic transplant. Blood was obtained before and after magnesium transfusions. Immunophenotypic analysis of T and NK cell NKG2D levels using commercially available monoclonal antibodies (CD3, CD16, CD56, CD4, CD8, CD314 [NKG2D]) was performed. Samples from patients demonstrating an increase in NKG2D expression were subsequently analyzed for ex vivo NK activity. Here, NK activity and cytotoxicity of Jurkat cells were assayed using standard laboratory techniques and changes > 2 fold were considered significant. A total of 7 patients were enrolled. Results: NKG2D expression on T and NK cell subsets were determined by flow cytometry using commercially available monoclonal antibodies. NK reactivity and killing of K562 were undertaken using standard cytotoxicity assays. Our findings indicate a significant response in five of the seven enrolled patients. NKG2D expression on CD8+ T cells increased by up to 31%. Conclusions: Our results suggest that magnesium infusions post allogeneic transplant are associated with augmented NKG2D expression on immune cells. Additional studies are needed to clarify the mechanisms by which therapeutic magnesium repletion restores the cytotoxicity of NK cells and T lymphocytes. Although the clinical utility of magnesium supplementation remains to be validated, our data indicate that NKG2D is regulated by magnesium post transplant and magnesium may play a key role in immune regulation.

A recombinant retroviral system was used for the analysis of early HIV breakthrough infection in the presence of antiviral drugs. The use of replication-defective HIV allowed a quantitative analysis of a single cycle of infection. This report characterizes this recombinant HIV system and demonstrates it's validity in comparison to standard assays. It is demonstrated that the protease inhibitor XM323 inhibits both early and late events in the HIV life-cycle, while dextran sulphate inhibits only early events. In addition, it is shown that this system can be used for detecting and quantitating drug resistant HIV. Thus, the use of this system may provide both novel information about the stage of the viral life-cycle inhibited and a preliminary assessment of the mechanism(s) responsible for breakthrough infection in the presence of antiretroviral drugs.

Mantle cell lymphoma (MCL) is associated with a significant risk of therapeutic failure and disease relapse, but the biological origin of relapse is poorly understood. Here, we prospectively identify subpopulations of primary MCL cells with different biologic and immunophenotypic features. Using a simple culture system, we demonstrate that a subset of primary MCL cells co-cultured with either primary human mesenchymal stromal cells (hMSC) or murine MS-5 cells form in cobblestone-areas consisting of cells with a primitive immunophenotype (CD19−CD133+) containing the chromosomal translocation t (11;14)(q13;q32) characteristic of MCL. Limiting dilution serial transplantation experiments utilizing immunodeficient mice revealed that primary MCL engraftment was only observed when either unsorted or CD19−CD133+ cells were utilized. No engraftment was seen using the CD19+CD133− subpopulation. Our results establish that primary CD19−CD133+ MCL cells are a functionally distinct subpopulation of primary MCL cells enriched for MCL-initiating activity in immunodeficient mice. This rare subpopulation of MCL-initiating cells may play an important role in the pathogenesis of MCL.

PDCD2 is an evolutionarily conserved eukaryotic protein with unknown function. The Drosophlia PDCD2 ortholog Zfrp8 has an essential function in fly hematopoiesis. Zfrp8 mutants exhibit marked lymph gland hyperplasia that results from increased proliferation of partially differentiated hemocytes, suggesting Zfrp8 may participate in cell growth. Based on the above observations we have focused on the role of PDCD2 in human cancer cell proliferation and hypothesized that aberrant PDCD2 expression may be characteristic of human malignancies. We report that PDCD2 is highly expressed in human acute leukemia cells as well as in normal hematopoietic progenitors. PDCD2 knockdown in cancer cells impairs their proliferation, but not viability relative to parental cells, supporting the notion that PDCD2 overexpression facilitates cancer cell growth. Prospective analysis of PDCD2 in acute leukemia patients indicates PDCD2 RNA expression correlates with disease status and is a significant predictor of clinical relapse. PDCD2's role in cell proliferation and its high expression in human malignancies make it an attractive, novel potential molecular target for new anti-cancer therapies.

Several epidemiological studies have suggested a link between melanoma and breast cancer. Metabotropic glutamate receptor 1 (GRM1), which is involved in many cellular processes including proliferation and differentiation, has been implicated in melanomagenesis, with ectopic expression of GRM1 causing malignant transformation of melanocytes. This study was undertaken to evaluate GRM1 expression and polymorphic variants in GRM1 for associations with breast cancer phenotypes. Three single nucleotide polymorphisms (SNPs) in GRM1 were evaluated for associations with breast cancer clinicopathologic variables. GRM1 expression was evaluated in human normal and cancerous breast tissue and for in vitro response to hormonal manipulation. Genotyping was performed on genomic DNA from over 1,000 breast cancer patients. Rs6923492 and rs362962 genotypes associated with age at diagnosis that was highly dependent upon the breast cancer molecular phenotype. The rs362962 TT genotype also associated with risk of estrogen receptor or progesterone receptor positive breast cancer. In vitro analysis showed increased GRM1 expression in breast cancer cells treated with estrogen or the combination of estrogen and progesterone, but reduced GRM1 expression with tamoxifen treatment. Evaluation of GRM1 expression in human breast tumor specimens demonstrated significant correlations between GRM1 staining with tissue type and molecular features. Furthermore, analysis of gene expression data from primary breast tumors showed that high GRM1 expression correlated with a shorter distant metastasis-free survival as compared to low GRM1 expression in tamoxifen-treated patients. Additionally, induced knockdown of GRM1 in an estrogen receptor positive breast cancer cell line correlated with reduced cell proliferation. Taken together, these findings suggest a functional role for GRM1 in breast cancer.

Plitidepsin (Aplidin), an antitumor agent of marine origin, presently is undergoing phase II/III clinical trials, and has shown promise for the treatment of lymphoma. Here, we describe the antitumor effects of plitidepsin alone and in combination with rituximab and investigated the effects of each drug and the combination on the cell cycle and mechanism of cell death. Several Diffuse Large Cell Lymphoma (DLCL) lines and Burkitt cell lines were tested for sensitivity to plitidepsin and rituximab. All DLCL and Burkitt lymphoma cell lines were inhibited by plitidepsin in nanomolar concentrations, while rituximab sensitivity varied among different cell lines. Ramos and the RL cell lines proved sensitive to rituximab and were used to test the effects of each of the two drugs. The two agents exhibited synergism at all tested concentrations. For in vivo studies, irradiated athymic nude mice were engrafted with the Ramos lymphoma. Treatment was initiated when the tumors were ~0.5 cm in diameter, and toxic and therapeutic effects were monitored. In the in vivo study, additive effects of the combined two drugs, was demonstrated without an increase in host toxicity. The in vitro synergy and the in vivo additive antitumor effects without an increase in host toxicity with two relatively non-marrow suppressive agents encourages further development of this combination for treatment of aggressive B-cell lymphomas.

The toxic effects of various concentrations of 2',3'-dideoxycytidine (ddC), 2',3'-dideoxy-2',3'-didehydrothymidine (D4T), and 2',3'-dideoxyinosine (ddI) on CEM cells after 4 days of culture were assessed by measuring cell viability, mitochondrial DNA (mtDNA) content, and mitochondrial morphology. Cell viability and mtDNA content in drug-treated cultures were significantly reduced in a concentration-dependent fashion in comparison with cell viability and mtDNA content in untreated cultures. Cells in the treated cultures also showed significant changes in their mitochondrial morphologies which included distortion and reduction of the cristae and numerous vesicles. Unique features of the morphological changes were associated with each drug. The decrease in cell viability and mtDNA content and the increase in mitochondrial ultrastructural changes were directly related to the concentrations of the drugs used. The potencies of these compounds in reducing cell viability, mtDNA content, and normal mitochondria were in the order ddC > D4T > ddI. Comparison of the three assays used demonstrated that mtDNA content is a significantly more sensitive measure of drug toxicity than cell viability and mitochondrial morphology for the three compounds studied.

We report the isolation of St. Louis Encephalitis (SLE) virus from a mature male killer whale (Orcinus orca). This represents the first isolation of SLE virus from a marine mammal. The animal presented with reduced appetite, rapidly became lethargic and subsequently died. Virus-induced CPE was observed in a dolphin cell line, SP-1K (ATCC CCL 78), inoculated with brain, kidney, and lung tissues obtained at necropsy. Electron microscopy of infected SP-1K cells revealed the presence of virions having morphology and size resembling members of the Flaviviridae. Final identification as SLE virus was made by neutralization and immunofluorescence staining tests.

Differentiation agents such as 12-O-tetradecanoylphorbol-13-acetate (TPA) engage cell signaling pathways that activate downstream transcriptional programs necessary for cell differentiation. Recent evidence has indicated microRNAs (miRNAs) are an integral part of these transcriptional programs, which target key proteins and impact cell growth thereby facilitating changes required for differentiation. To further investigate the role of miRNAs in cell growth and differentiation, we focused on miR-22, a miRNA induced by TPA in the HL-60 leukemia cell line model of monocytic differentiation. TPA-induced miR-22 transcription was found to be downstream of the protein kinase c (PKC)–extracellular regulated kinase (ERK) signaling module, a pathway central to the growth and differentiation of many different cell types. Enforced miR-22 expression inhibited the growth of several different cancer cell lines, causing an accumulation of cells in the G1 phase of the cell cycle. The mechanism of miR-22’s inhibitory effects involves targeting of the obligate c-Myc binding partner Max. Enforced miR-22 expression presumably lowers Max levels available for Myc binding, which differentially influenced the transcription of downstream targets of the Myc–Max complex. Our study provides additional support for miRNAs targeting key cellular regulatory microcircuits such as those governed by the Myc–Max transcriptional complex as well as their being active participants in cell growth and differentiation.

MicroRNAs are short non-coding RNA molecules able to affect stability and/or translation of mRNA, thereby regulating the expression of genes involved in many biological processes. We report here that microRNAs miR-27a and miR-451 are involved in activating the expression of P-glycoprotein, the MDR1 gene product that confers cancer cell resistance to a broad range of chemotherapeutics. We showed that expressions of miR-27a and miR-451 were up-regulated in multidrug resistant (MDR) cancer cell lines A2780DX5 and KB-V1, as compared with their parental lines A2780 and KB-3-1. Treatment of A2780DX5 cells with the antagomirs of miR-27a or miR-451 decreased the expression of P-glycoprotein and MDR1 mRNA. In contrast, the mimics of miR-27a and miR-451 increased MDR1 expression in the parental cells A2780. The sensitivity to and intracellular accumulation of cytotoxic drugs that are transported by P-glycoprotein were enhanced by the treatment with the antagomirs of miR-27a or miR-451. Our results demonstrate for the first time the roles of microRNAs in the regulation of drug resistance mediated by MDR1/P-glycoprotein, and suggest the potential for targeting miR-27a and miR-451 as a therapeutic strategy for modulating MDR in cancer cells.

Allogeneic hematopoietic stem cell transplantation provides curative therapy for some patients with advanced hematologic malignancies. Disease response after allogeneic transplant is, at least in part, mediated by donor immune cells. In this report we describe a cellular therapy using haploidentical peripheral blood stem cells administered after very low dose total body irradiation (TBI) (100cGy). The donor cells were anticipated to be rejected, so no graft-versus-host (GVHD) prophylaxis was used. Patients with persistent disease beyond 8 weeks could be further treated with infusions of irradiated haploidentical donor cells. Of the 10 patients enrolled in the study, durable engraftment of allogeneic cells was seen in one patient. Two patients with resistant relapsed acute myelogenous leukemia (AML) had a disease response. Analysis of T cell reactivity from one patient who achieved a complete response but did not have durable engraftment of donor cells indicated that disease response was associated with the generation of host-derived anti-leukemic cytotoxic CD8+ T cells that reacted with an AML-associated proteinase 3 epitope. Results from this patient suggest that allogeneic therapy induced a host anti-tumor response associated with cytotoxic T cells reactive with a low affinity self-antigen.

Metabotropic glutamate receptor 1 (GRM1) has an established oncogenic role in melanoma. Growing evidence supports a similar role in breast cancer. We have previously shown that GRM1 is not only expressed in human breast cancers, but that levels of expression correlate with clinical outcomes with tamoxifen treatment, and that GRM1 knockdown reduces breast cancer cell viability and growth. Others have shown that GRM1 modulating drugs also reduce viability and growth of estrogen receptor (ER) negative breast cancer cell lines. Riluzole, a postulated inhibitor of glutamate release, has been evaluated in pre-clinical studies in melanoma. Early clinical trials have shown promising results for this disease. However, the mechanistic effects of riluzole have not been well-defined. Therefore, we evaluated the functional activity of riluzole in breast cancer. A molecularly diverse set of ER+ and ER- breast cancer cell lines with variable GRM1 expression were evaluated. Cell lines were treated with either riluzole or BAY 36-7620 (non-competitive GRM1 antagonist) or their combination. Treatment with either drug reduces cell number and viability, inhibits cell proliferation, and alters expression of cell cycle and apoptotic pathway genes as determined by gene microarray analysis. Drug treatment produces cell line-dependent effects on markers for proliferation, cell cycle, DNA damage, and apoptosis. Riluzole induces G2/M arrest in all cell lines tested. More specifically, riluzole induces mitotic arrest as demonstrated by changes in histone H3 phosphorylation at serine 10 and cyclin B level. Treatment with BAY 36-7620 induces a modest G2/M arrest and increase in the sub G1 population in a subset of cell lines. However, BAY 36-7620 does not induce mitotic arrest. The combination of riluzole and BAY 36-7620 results in increased cell death and decreased proliferation in all cell lines tested. Our data suggest that either riluzole or BAY 36-7620 induce breast cancer cell death. However, riluzole may modulate the activity of intracellular targets independent of GRM1. As riluzole is an FDA-approved drug, it could be quickly moved into a clinical trial and may provide a novel therapeutic approach in the treatment of breast cancer. Citation Format: Sonia C. Dolfi, Daniel J. Medina, Shridar Ganesan, Alexei Vazquez, Kim M. Hirshfield. Riluzole effectively modulates cell cycle and cell death in a molecularly diverse set of breast cancer cell lines. [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 4463. doi:10.1158/1538-7445.AM2015-4463

Mantle cell lymphoma (MCL) is a distinct form of non-Hodgkin's lymphoma (NHL) derived from CD5+ B cells. MCL cells overexpress cyclin D1 as a consequence of translocation of the gene into the immunoglobulin heavy-chain gene locus. MCL is an aggressive form of NHL with frequent relapses after standard-dose chemotherapy. In this context, a variety of novel therapies for patients with MCL have been investigated. In this study, we use an expanded panel of attenuated adenoviruses to study adenovirus-mediated cytotoxicity of MCL cells. Our results demonstrate: 1) adenovirus infection of MCL cells despite the absence of receptor/coreceptor molecules known to be important for adenovirus infection of other cells types; 2) cytotoxicity of MCL cells after infection with specific adenovirus mutants; 3) a high degree of cytotoxicity after infection of some patient samples with viruses lacking the E1B 19k "antiapoptotic" gene; and 4) cytotoxicity after infection with viruses containing mutations in E1A pRb or p300 binding. The extent of cytotoxicity with the panel of viruses demonstrated interpatient variability, but 100% cytotoxicity, as determined by molecular analysis, was detected in some samples. These studies provide the foundation for: 1) the development of adenoviruses as cytotoxic agents for MCL and 2) analyses of key regulatory pathways operative in MCL cells.

Purpose: Vaccines, cytokines, and other biologic-based therapies are being developed as antineoplastic agents. Many of these agents are designed to induce an autologous immune response directed against the malignancy. In contrast, hematopoietic stem-cell transplantation is being developed as a form of allogeneic immunotherapy. This study tests the tolerance and antineoplastic activity of sequential infusions of partially HLA-matched allogeneic blood mononuclear cells (obtained from relatives) when administered outside of the context of a hematopoietic stem-cell transplantation. The cells are irradiated to prevent graft-versus-host disease. Patients and Methods: Fifteen patients with relapsed or refractory malignancies for which no standard therapy was available were enrolled onto a clinical trial designed to assess the tolerability and antineoplastic effects of irradiated partially HLA-matched blood mononuclear cells obtained from relatives. Results: There was disease regression in three patients with metastatic renal cell carcinoma during treatment. There was disease progression in six patients with metastatic renal cell carcinoma and two patients with metastatic melanoma during treatment. There was no change in disease state in several other patients. Conclusion: Irradiated allogeneic blood mononuclear cells administered outside the context of hematopoietic stem-cell transplantation may induce disease responses in patients with relapsed or refractory malignancies. Transfusion of irradiated allogeneic blood mononuclear cells should be developed further as a novel therapeutic antineoplastic approach.

Adenovirus infection represents a cellular stress that induces host cell pro-apoptotic responses. To overcome this barrier to productive infection, viral polypeptides modulate a variety of host cell pathways. The interface of these early viral gene products with key cellular regulatory proteins has provided considerable information concerning basic cellular mechanisms operative in cell cycle regulation, transcriptional control and apoptosis. The overlap of these mechanisms with those impacted during oncogenesis provides the opportunity to use adenoviruses and adenovirus mutants to characterize the state of key regulatory pathways in specific malignant cells. For example, adenoviruses mediate cytotoxicity after infection of chronic lymphocytic leukemia (CLL) cells, mantle cell lymphoma (MCL) cells and multiple myeloma cell lines. Specific adenovirus mutants demonstrate enhanced cytotoxicity and, in many cases, apoptosis is not the primary mechanism of cell death. Analysis of these infections with respect to both the features of the primary malignant cell and the mechanisms of adenovirus-mediated cytotoxicity holds the prospect of providing novel insights into the status of key regulatory pathways in individual patient malignant cells. These studies also hold the prospect of supporting the development of specific attenuated adenoviruses as therapeutic agents with selective cytotoxicity for specific primary lymphoid malignancies.

Metabotropic glutamate receptor 1 (GRM1), first recognized as an important factor in the central nervous system, has more recently been implicated in melanomagenesis and breast cancer pathogenesis. Oncogenic mediators of GRM1-associated effects include both MAPK and AKT signaling cascades. Modulation of GRM1 activity in melanoma and estrogen receptor negative (ER-) breast cancer cells inhibits anchorage independent growth, migration, proliferation, and/or downstream activation of Akt and ERK. Data from our laboratory show that a significantly higher fraction of breast tumors express GRM1 compared to normal breast tissue, and GRM1 expression is more highly correlated with ER positivity. Moreover, higher GRM1 expression in human ER+ breast cancers treated with the anti-estrogen tamoxifen associates with a shorter distant metastasis free survival as compared to low expressors further supporting a critical role in ER+ breast cancer. We hypothesize that ER has both genomic and non-genomic effects on GRM1. We evaluated the effect of hormonal treatment on GRM1 protein expression in ER+ MCF7 and ER- MDA-MB-231 breast cancer cells. Estradiol increases GRM1 expression, and this effect is abrogated by the anti-estrogen tamoxifen in MCF7 but not in MDA-MB-231 cells. These genomic effects may be exerted through three putative ER binding sites within the GRM1 promoter. We have confirmed that ER binds to one of these sites by chromatin immunoprecipitation, further supported by ChiPSeq data. GRM1 promoter activity is increased by estradiol treatment using a luciferase reporter assay validating transcriptional activation by ER. To support a non-genomic role for ER with GRM1, we have shown that ER physically interacts with GRM1 in breast cancer cells by in vitro proximity ligation assay and by co-immunoprecipitation in immortalized mouse mammary epithelial cells (iMMECs) stably expressing GRM1. Stable introduction of GRM1 into iMMECs, which lack endogenous GRM1, reduces sensitivity to tamoxifen as compared to control iMMECs. In MCF7 cells, the combination of tamoxifen with GRM1 modulators riluzole or BAY 36-7620 produces synergistic effects. As estradiol activates MAPK signaling in breast cancer cells, we hypothesize that this may be mediated by both the physical interaction of GRM1 and ER and the indirect effects on GRM1 transcription. Results of these studies suggest that GRM1 may be a valuable therapeutic target in ER+ breast tumors. Citation Format: Sonia C. Dolfi, Madhura S. Mehta, David Kornblum, Andrew Boughton, Hussein Rahim, Daniel Medina, Kim M. Hirshfield. Regulation of GRM1 by estrogen receptor in breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4457. doi:10.1158/1538-7445.AM2014-4457

The prognosis of patients with tumors expressing P-glycoprotein (P-gp), the MDR1 gene product, is generally poor. It is assumed that this is due to decreased tumor responsiveness that results from decreased drug accumulation. We observed that treatment of animals bearing MDR1-transfected leukemic cells with P-gp substrates (i.e., drugs that are transported by P-gp) significantly worsened host survival compared to treatment with vehicle or non-P-gp substrates. This effect was seen with cancer chemotherapeutic agents (paclitaxel and vincristine) and with the MDR modulator, trans-flupenthixol. To determine the mechanism(s) underlying this observation, we studied alterations in pharmacokinetics, pharmacodynamics, and metastasis. We found that the drug-induced acceleration of disease was associated with increased metastases. P-gp(+) cells treated with P-gp substrates demonstrated several pro-metastatic features, including membrane ruffling and invasion through a hepatocyte monolayer. These results suggest that the treatment of MDR tumors with P-gp substrates may produce changes in malignant behavior that could adversely affect therapeutic outcomes.

A variety of cell lines were infected with replication-defective recombinant retroviruses in the presence of stavudine (d4T). Cells which were infected despite the presence of d4T were isolated and subjected to infection with other retroviruses [replication-competent human immunodeficiency virus (HIV), replication-defective HIV or replication-defective recombinant murine retroviruses]. Each of the host cell types tested had a small subset of cells that were infected with HIV or murine retroviruses in the presence of d4T. Some of these infected cells could be infected repeatedly at high efficiency in the presence of d4T. This phenotype of ‘persistent refractoriness’ to the antiviral effects of d4T could be overcome by the addition of 5-fluoro-2-deoxyuridine (floxuridine) to d4T. The d4T–floxuridine combination also had potent antiretroviral effects in primary blood mononuclear cells.

Human immunodeficiency virus (HIV) resistance to the nonnucleoside reverse transcriptase inhibitors emerges very rapidly under selection in culture and in patients. In contrast, zidovudine (3'-azido-3'-deoxythymidine [AZT])-resistant HIV generally emerges in patients only after more-prolonged therapy. Although HIV can be cultured from many patients shortly after the initiation of AZT treatment, characterization of the virus that is cultured generally indicates that it is sensitive to AZT. To initiate an evaluation of the mechanisms contributing to early HIV breakthrough in the presence of AZT and other nucleoside analogs, we have utilized replication-defective HIV encoding reporter genes. These recombinant HIV allow a quantitative analysis of a single cycle of infection. Results with these defective HIV indicate that early infection in the presence of AZT often results from the infection of a cell which is refractory to the antiretroviral effects of AZT. Characterization of a cell line derived from one such cell has demonstrated decreased accumulation of AZT triphosphate, increased phosphorylation of thymidine to thymidine triphosphate, and increased levels of thymidine kinase activity. In addition, AZT inhibition of replication-competent HIV infection is also significantly impaired in this cell line. Attempts to detect and characterize the mechanisms responsible for early viral infection after initiation of AZT therapy may result in the development of new strategies for prolonged suppression of viral infection prior to the emergence of drug-resistant virus.

Cytomegalovirus (CMV) and the human immunodeficiency virus type 1 (HIV-1) may interact in the pathogenesis of AIDS. We compared CMV replication in human osteosarcoma (HOS) cells to that in HOS cells genetically engineered to contain an envelope-deficient HIV-1 proviral construct (designated HOS-HXG). Following acute CMV infection of each cell line, HOS-HXG cells contained higher numbers of intranuclear CMV nucleocapsids than did HOS cells. Infectious CMV could be persistently detected in culture supernatant fluids of the CMV-infected HOS-HXG cells, whereas CMV was lost over several weeks from HOS cells infected with CMV in parallel. HIV-1 CMV pseudotypes were not detected in supernatant fluids from CMV-infected HOS-HXG cells. On day 119 after CMV infection, these cultures were superinfected with HIV-1. These dually infected HOS-HXG cells produced infectious HIV-1 and exhibited markedly enhanced CMV replication compared to parental CMV-infected HOS-HXG cells. Two different HIV-1 tat gene function antagonists, Ro24-7429 and chemically modified antibodies to the Tat protein, did not inhibit the replication of CMV in either acute or persistent infections of HOS-HXG cells at concentrations that inhibited HIV-1 replication.

Prostate cancer stem cells or tumor initiating cells (TICs) represent a barrier to effective treatment due to their intrinsic resistance to current therapeutic modalities. Recent studies identified Bmi-1 (B-cell specific MMLV insertion site-1), a member of the polycomb family of chromatin remodeling complexes, as a major oncogenic protein that is highly expressed in, and regulates stem cells and prostate TIC self-renewal. We found that shRNA specific targeting or pharmacological inhibition of the critical stem cell and TIC protein Bmi-1 in cultured prostate tumors resulted in cell death. These studies were extended to demonstrate that Bmi-1 plays an equally critical role in prostate TIC maintenance in patient tumors, and that targeting Bmi-1 eliminates the subpopulation of TICs resistant to hormone ablation and currently used chemotherapies. We utilized a novel zebrafish xenograft of primary human prostate tumor model to identify candidate Bmi-1 inhibitory drugs and other drugs targeting TIC pathways for further preclinical and clinical testing. First, we isolated and characterized TICs from fresh human prostate tissues from patients undergoing resection, and then utilized the zebrafish primary xenograft model to evaluate TIC growth, and to define Bmi-1 and other stem cell associated pathways as bonafide TIC targets. Next, we investigated Bmi-1 and other TIC inhibitors in enriched prostate stem cells and the zebrafish model, and the results were confirmed in the mouse xenograft model to determine efficacy and toxicity. Zebrafish bearing Du145 xenografts were compared to fish bearing fresh human TICs, and the combinations of Bmi-1 inhibitor(s) with taxotere, a drug approved for use in the treatment of advanced prostate cancer were synergistic. Our studies are extended to determine the features of prostate TICs in zebrafish xenograft assays, and to study the effects of Bmi-1 inhibitors in sensitized microenvironments lacking the downstream targets P16INK4a and p19Arf, in order to analyze the changes in Bmi-1 targets regulating survival, proliferation, and cancer stem cell maintenance. The novel aspects of these studies are the growth inhibition of human prostate TICs, and the use of zebrafish as an in vivo model to determine Bmi-1 inhibitor efficacy, doses and combinations with conventional therapies. Bmi-1 inhibitors that target prostate cancer TICs may provide a new class of potent inhibitors that when used alone and in combination with other targeted therapy would represent an effective therapeutic management for patients with prostate cancer. Moreover, the use of zebrafish would allow the rapid generation of response to therapy data that would facilitate the development of drugs targeted to prostate TICs. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4279.

In studies examining potential interactions between ganciclovir (GCV) and either zidovudine (AZT) or didanosine (DDI) in H9 cells, GCV was found to consistently reduce the anti-human immunodeficiency virus type 1 potency of both AZT and DDI. In the presence of GCV, the 50% effective doses of AZT and DDI were increased three- to sixfold, depending on the molar ratio of drugs and the measure of human immunodeficiency virus type 1 replication (p24 antigen, reverse transcriptase activity, or infectious virus yield). Multiple dose-effect analysis revealed strong antagonism between GCV and either AZT or DDI (combination indices, 2.2 to 6.7). This antagonistic effect occurred at drug concentrations that were well below the cytotoxic range. At higher drug concentrations, the combination of GCV and AZT was synergistically cytotoxic (combination indices, less than 1.0), whereas GCV and DDI were only additively cytotoxic (combination indices, ca. 1.0). Thus, the combination of GCV with AZT or DDI may result in antiviral antagonism and either synergistic (AZT-GCV) or additive (DDI-GCV) cytotoxicity.

Purpose: Emerging evidence suggests a role for glutamate and its receptors in the pathogenesis of several forms of cancer. Investigators from our institution have recently shown that the metabotropic glutamate receptor 1 plays a significant role in the pathogenesis of melanoma and that inhibition of this pathway by the glutamate release inhibitor Riluzole results in suppression of cell growth. In this study we test the hypothesis that inhibition of metabotropic glutamate receptors by Riluzole in mantle cell lymphoma cells will result in a reduction of cell proliferation/survival. Experimental Design: Mantle cell lymphoma (MCL) cell lines (MINO, JEKO and Rec-1) were treated with several concentration of the glutamate release inhibitor Riluzole. Samples were collected after 24, 48 and 72 hours of treatment and evaluated for cell viability and cell number by trypan blue exclusion, and cell proliferation and cell cycle analysis by flow cytometry. Apoptosis was evaluated by PARP cleavage and staining for Annexin V. Results: All three MCL cell lines treated with Riluzole demonstrated a significant decrease in cell number and cell viability with an IC50=25uM. MCL cells treated with Riluzole showed a block in S and G2/M of the cell cycle followed by apoptosis. Apoptosis was confirmed by annexin V expression and by PARP cleavage. Conclusions: Our date demonstrates that glutamate blockade with Riluzole results in the inhibition of mantle cell lymphoma proliferation, cell viability and the induction of cell cycle arrest at S and G2/M phases of the cell cycle. In addition, we show that the loss of cell viability is due to the activation of the apoptotic pathway. These preliminary findings suggest that expression of metabotropic glutamate receptors may be important in the pathogenesis and that targeting this pathway may provide a novel and effective therapy. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C81.

Abstract 3533 Poster Board III-470 Umbilical Cord Blood (UCB) is a readily available, alternate donor source for allogeneic Hematopoietic Stem Cell (HSC) transplantation and can be used with lower stringency HLA-matching between donor and host. However, only limited numbers of cells are available and non-engraftment or delayed engraftment occurs often when recipients receive single UCB units that contain < 2.5 × 107 TNC/kg recipient body weight. This excludes single UCB as a donor source for many adult patients who might otherwise benefit from an UCB transplant. Both immunologic and non-immunologic mechanisms may contribute to UCB HSC engraftment failure. UCB T-cells are phenotypically and functionally immature with a high percentage of CD45RA+ T cells and T cells are known to facilitate engraftment in human HSC transplantation. Co-transplantation of irradiated T-cells supported engraftment in an immunocompetent mouse transplant model without increasing GvHD (Waller et al. Blood94: 3222,1999). The working hypothesis for his study is that the irradiated third party peripheral blood mononuclear cells (PBMNCs) induce a cytokine or cellular response that facilitates hematopoietic engraftment. Long-term culture initiating cell (LTC-IC) frequencies determined with limiting dilution assays were statistically higher when either purified UCB derived CD34+ cells or CB MNCs cells were plated with irradiated PBMNCs (Figure 1). Figure 1 Figure 1. To assess the impact of irradiated third party PBMCs on UCB engraftment we utilized sub-lethally irradiated NOD/SCID-IL2Rgnull mice in the presence and absence of irradiated third-party human PBMNCs. After sublethal irradiation (240 cGy) female 8 week-old animals were transplanted with either UCB MNCs corresponding to 8×103 (n=5) or 2.66×103 (n=9), or 8.88×102 CD34+ cells (n=9) with or without co-transplantation of 1×106 irradiated (2500 cGy) PBMNCs, and 4 animals received only irradiated PBMNCs as the control group. Engraftment levels are compared by calculating SCID repopulating cell (SRC) frequency. Co-transplantation of PB MNCs with UCB MNCs provided a steady, statistically significant increase in both short-term and long term hematopoietic engraftment (Figure 2). Figure 2 Figure 2. In these pre-clinical studies, we have confirmed in vitro effects on LTIC formation and in vivo UCB graft-enhancing effects of irradiated PBMNCs. If applied in clinic, this cellular therapy option might overcome a major barrier to successful allogeneic UCB HSC transplantation: engraftment failure, making the procedure more applicable and safer. Disclosures: No relevant conflicts of interest to declare.

2552 Background: We previously demonstrated the safety and efficacy of HLA-haploidentical blood mononuclear cells (MNCs) administered in the absence of preparative therapy to patients with metastatic renal cell carcinoma (RCC) (J Clin Oncol 21:3785–91.2003). The efficacy of this therapy is evaluated further in patients with advanced malignancies. Methods: Patients with advanced malignancies who had HLA- haploidentical donors were enrolled. Donors underwent 12–15 L leukapheresis. MNCs were processed by irradiation (25 Gy) and immediately infused. Disease evaluation was undertaken every 8 weeks. Repeat infusions were given every 8 weeks until disease progression. Results: 30 patients with diverse diagnoses, including 9 patients with a hematological malignancy were treated. Three of 13 patients with RCC had disease response, and 1 of 2 patients with melanoma had a mixed response. A patient with imatinib mesylate-refractory chronic myelogenous leukemia (CML) had a transient response. A patient with refractory acute myelogenous leukemia (AML) had disease response in conjunction with therapy. Treatment was associated with minimal toxicity and radiographic responses in patients with RCC did not occur until after 2–3 treatments. Host CD8+ cells reactive with the Pr-1 peptide of proteinase 3 were induced in association with disease response in a patient with AML. Additional studies identifying disease targets and mechanisms by which infusion of irradiated HLA-haploidentical cells are associated with disease response are ongoing. Conclusions: Disease response is seen with irradiated allogeneic MNCs administered outside the context of hematopoietic stem-cell transplantation. Evidence for anti-tumor activity is seen in isolated patients with RCC, melanoma, CML and AML. The temporal nature of the response in RCC in combination with the very limited survival of the infused cells raises the possibility of induction of a host-mediated anti-tumor effect. This hypothesis is supported by induction of host CD8+ T cells reactive with a tumor-associated peptide in a patient with AML. Given the lack of toxicity, broad availability of related haploidentical donors and the relative low financial cost, this form of cellular therapy should be developed further. No significant financial relationships to disclose.

Aplidin (dehydrodidemnin B, C57H89N7O15) (APLD) is a novel antitumor agent isolated from the Mediterranean tunicate (seasquirt) Aplidium albicans. APLD has shown impressive in vitro and in vivo activity against different human cancer cells and has recently entered Phase II clinical trials in a variety of solid tumors following promising toxicity and pharmacological properties seen in Phase I studies. Fatigue and muscular pain were the most prevalent toxicities at 5 mg/m2 iv 3 h every other week or 3.4 mg/m2/wk with little or no bone marrow toxicity. APLD inhibits protein synthesis via GTP-dependent elongation factors 1-alpha and ornithine decarboxylase (ODC) activity, induces rapid p53-independent apoptosis in vitro, cell cycle perturbation and alteration of gene expression at early times after treatment. APLD inhibits vascular endothelial growth factor (VEGF) secretion and vascular endothelial growth factor-receptor 1 (VEGF-R1/flt-1), preventing autocrine stimulation in the human lymphoid leukemic cell line MOLT-4 cells and in AML blasts. APLD is a potent inhibitor of human myeloid leukemia cell lines (K-562, HEL and HL60), as well as fresh blast cells obtained from patients with both ALL and AML and is more potent than Idarubicin. Cytototoxic doses effective against multiple myeloma cells and fresh pediatric and adult ALL/AML blasts are achievable in plasma and are well below the recommended dose, thus a positive therapeutic index is anticipated. Moreover, the lack of cross resistance with conventional agents against fresh pediatric and adult AML/ALL blasts except fludarabine and Gemcitabine makes APLD an attractive therapeutic choice. Characterization of gene expression profile is currently underway in an attempt to generate a molecular fingerprint of sensitivity/resistance to APLD that will be validated in phase II clinical studies. Based on in vitro antileukemic effect of APLD as well as early results of clinical trials, a systematic study of drug combinations with Aplidin (APLD), for use possible in hematologic malignancies was undertaken. Three cell lines viz. K562 (acute myeloid leukemia), CCRF-CEM (acute lymphocytic leukemia), and SKI-DLCL (diffuse large cell lymphoma) were used for combination studies. Cytarabine and mitoxantrone were found to be synergistic in combination with APLD in all 3 cell lines as assessed by the Chou-Talalay combination index analysis. Since cytarabine and APLD produced impressive synergistic cell kill in all three cell culture models, the combination was further tested in the CCRF-CEM ALL xenograft model in SCID mice. APLD (0.7 mg/Kg) potentiated the antitumoral effect of cytarabine (50mg/Kg) in vivo. Addition of APLD to cytarabine treatment in xenograft model resulted in greater than 50% reduction in tumor size as compared to the untreated group. T/C ratios indicated that the effect of the combination was maximal at day 5 but was still maintained on day 8 (T/C on day 3 = 0.614; day 5= 0.403 and day 8= 0.703). The preclinical results with APLD in leukemias and lymphomas, as a single agent and in combination with cytarabine provide the basis for implementation of a phase II program in resistant relapsed leukemias and lymphomas.

The evaluation of the protein binding partner(s) of biologically important proteins is currently an area of intense research, especially since the development of the yeast two-hybrid assay. However, not all protein-protein interactions uncovered by this assay are biologically relevant and another confirmatory assay must be performed. Ideally, this assay should be rapid, versatile and performed under conditions which mimic the 'normal' physiological state as closely as possible. Towards this goal, we have constructed two eukaryotic expression vectors that facilitate the purification of a protein of interest, along with any associated proteins, from mammalian cells. These vectors incorporate the following features: (i) a tetracycline-responsive promoter so that the level of protein production can be regulated; (ii) an N-terminal glutathione S-transferase tag or a triple repeat of the HA1 epitope, to facilitate purification of the protein either by glutathione affinity chromatography or immunoprecipitation, respectively, followed by a multiple cloning site; (iii) the gene for the enhanced green fluorescent protein (for detection of the presence of the fusion protein and subcellular localization); (iv) a puromycin marker for the selection of stable transformants; (v) a truncated EBNA protein and oriP sequence for episomal replication of the vector. These latter two features permit expansion of small cultures of transfected cells under puromycin selection, thereby increasing the amount of tagged protein that can be purified. We show that these vectors can be used to direct the doxycycline-inducible expression of tagged proteins and to recover tagged CIP1-p21 protein complexes from HeLa cells. Furthermore, we show that these tagged p21-purified complexes contain both cyclin A and Cdk2, which are known to interact with p21, but not beta-actin.