Citations

Urinary bladder cancer (UBC) is the most common malignancy of the urinary tract in humans, with an estimated global prevalence of 1.1 million cases over 5 years. Because of its high rates of recurrence and resistance to chemotherapy, UBC is one of the most expensive cancers to treat, resulting in significant health care costs. The development of innovative molecular and cellular tools is necessary to refine patient stratification and help predict response to treatment. Urine is an underused resource of biological components shed from bladder tumors, such as exfoliated cells and extracellular vesicles, that could serve as molecular fingerprints and provide valuable biological insights into tumor phenotype and mechanisms of resistance to chemotherapy. Additionally, characterization of urine-derived extracellular vesicles and cells could be used as reliable biomarkers for prediction of response to neoadjuvant therapy.

Abstract Patients with glioblastoma (GBM) have a median survival of 15 months despite aggressive treatment. Immunosuppressive monocytes are heavily infiltrated in these tumors and in patients’ circulation. Treatment-related pseudo-progression confounds outcome assessment by MRI. Thus, there is a need for additional non-invasive methods to assess treatment response. Extracellular vesicles (EVs) contain tumor-specific microRNA (miRNA) cargo that could serve as a liquid biopsy to distinguish true progression from treatment-related pseudo-progression. We had found significant differences in plasma EVs molecular profile (i.e. miRNA signatures) between GBM patients and healthy donors. Our overall hypothesis is that these differences reflect the EVs cell of origin. Our goal in this project was to develop a fluorescent staining paradigm by flow cytometry to distinguish EVs from different cells in vitro and determine differences in EV miRNA expression profile between GBM and monocytic cell-derived EVs. Gleolan (5-ALA) is an FDA-approved orally available agent for fluorescence-guided resection of GBM tumors. It is metabolized to protoporphyrin IX (PpIX) in GBM cells but not in non-neoplastic cells and has been reported to aid in the detection of GBM-derived EVs by flow cytometry. However, distinguishing between GBM-derived EVs and EVs from other cells of origin has not been described. We co-cultured human GBM cells (dBT114 or dBT116) and CD14+ monocytes for 72 hours in the presence or absence of 5-ALA. EVs were isolated by ultracentrifugation and stained for CD11b (myeloid cell marker). ImageStream Imaging Flow Cytometry was performed showing clear differentiation between PpIX+ EVs from GBM cells and CD11b+ EVs from monocytes. Interestingly, a small number of double-positive EVs (presumably representing monocyte-derived EVs that had taken up PpIX after phagocytizing GBM cells) were also present. Taken together, we were able to optimize a technique to distinguish EVs originating from GBM and monocytes for further characterization by short non-coding RNA sequencing.

Abstract Background: Upamostat is an orally available small molecule serine protease inhibitor that is a highly potent inhibitor of trypsin 1, trypsin 2 and trypsin 3 (PRSS1/2/3) as well as urokinase-type plasminogen activator (uPA) which are expressed in many cancers and mediate cell migration, invasion and tissue remodeling. Opaganib (ABC294640), a novel, orally available small molecule is a specific inhibitor of sphingosine kinase 2 (SPHK2), which phosphorylates sphingosine to sphingosine-1-phosphate (S-1-P). While proliferation induced by S-1-P is regulated by both sphingosine kinase 1 (SPHK1) and SPHK2, SPHK2 appears to be more involved in cancer. We aimed to investigate the potential antitumor effect of upamostat and opaganib, individually and in combination, on cholangiocarcinoma (CCA) patient derived xenografts (PDX) in nude mice. Methods: PAX165, a PDX from a surgically resected CCA, expresses substantial levels of SPHK2, PRSS1, PRSS2 and PRSS3. 4 groups of 18 mice were treated with either drug or both. Mouse weights and tumor volumes were measured. In addition, experiments were conducted using the chorioallantoic membrane (CAM) of chicken embryos. Results: Table 1 shows the average tumor size for the control, upamostat, opaganib, and upamostat+opaganib groups at the study end point (Day 42). Tumor volumes in the upamostat, opaganib, and upamostat+opagnib groups were significantly decreased compared to the control group. The CAM experiments are ongoing and will be presented at the AACR Annual Meeting. Change in tumor volumes (mean) of CCA PDX after opaganib, upamostat or combination treatmentControlOpaganibUpamostatOpaganib+UpamostatPre-treatment129.9128.7118.8126.8Day 42198.6102.093.3186.09Percent change Day 0-42+53%-21%-21%-32%P value vs. control0.00020.00100.0008 Conclusion: This preclinical study demonstrated that upamostat and opaganib resulted in tumor regression in mice. Body weights of the mice showed no significant inter- or intra- group differences. The combination of upamostat and opaganib treatment showed greater regression compared to either upamostat or opaganib alone. Studies are underway to identify the molecular mechanisms of their interaction. Citation Format: Faizal Z. Asumda, Mohamed A. Hassan, Yo Han Kim, Nellie A. Campbell, Xin Luo, Daniel R. O'Brien, Sarah A. Buhrow, Joel M. Reid, Michael J. Moore, Vered Katz Ben-Yair, Reza Fathi, Mark L. Levitt, Fabrice Lucien-Matteoni, Jennifer L. Leiting, Mark J. Truty, Lewis R. Roberts. Effects of upamostat and opaganib on cholangiocarcinoma patient derived xenografts [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 3078.

Background Trans-acting programmed death-ligand 1 (PD-L1) derives from malignant cells in three known forms. High levels of secreted splice variant PD-L1 (sPD-L1), ADAM10/ADAM17-shed sPD-L1, and PD-L1-positive extracellular vesicles (evPD-L1) each predict poor prognosis and limited response to PD-(L)1 checkpoint inhibitors in cancer. To our knowledge, no clinical intervention has reduced any of these circulating forms of extracellular PD-L1. Here, we explore therapeutic plasma exchange (TPE) as a treatment to reduce circulating extracellular PD-L1. Results In patients with melanoma, sPD-L1 levels above 0.277 ng/mL predicted inferior overall survival. In patients undergoing TPE for non-malignant indications, each TPE session removed a mean 70.8% sPD-L1 and 73.1% evPD-L1 detectable in plasma. TPE also reduced total and ADAM10-positive extracellular vesicles. Conclusion Here, we report the first known clinical intervention to remove either sPD-L1 or evPD-L1 from plasma in vivo. TPE reduces plasma sPD-L1 and evPD-L1 in vivo and may have a role in treatment with immunotherapy. TPE may also prove useful in patients with other extracellular vesicle-related conditions.

Abstract Background Immunosuppression in glioblastoma (GBM) is an obstacle to effective immunotherapy. GBM-derived immunosuppressive monocytes are central to this. Programmed cell death ligand 1 (PD-L1) is an immune checkpoint molecule, expressed by GBM cells and GBM extracellular vesicles (EVs). We sought to determine the role of EV-associated PD-L1 in the formation of immunosuppressive monocytes. Methods Monocytes collected from healthy donors were conditioned with GBM-derived EVs to induce the formation of immunosuppressive monocytes, which were quantified via flow cytometry. Donor-matched T cells were subsequently co-cultured with EV-conditioned monocytes in order to assess effects on T-cell proliferation. PD-L1 constitutive overexpression or short hairpin RNA–mediated knockdown was used to determined the role of altered PD-L1 expression. Results GBM EVs interact with both T cells and monocytes but do not directly inhibit T-cell activation. However, GBM EVs induce immunosuppressive monocytes, including myeloid-derived suppressor cells (MDSCs) and nonclassical monocytes (NCMs). MDSCs and NCMs inhibit T-cell proliferation in vitro and are found within GBM in situ. EV PD-L1 expression induces NCMs but not MDSCs, and does not affect EV-conditioned monocytes T-cell inhibition. Conclusion These findings indicate that GBM EV-mediated immunosuppression occurs through induction of immunosuppressive monocytes rather than direct T-cell inhibition and that, while PD-L1 expression is important for the induction of specific immunosuppressive monocyte populations, immunosuppressive signaling mechanisms through EVs are complex and not limited to PD-L1.

Treatment with CD19-directed chimeric antigen receptor T cell (CART19) therapy has resulted in unprecedented clinical outcomes and was FDA-approved in acute lymphoblastic leukemia and non-Hodgkin B-cell lymphoma. However, its success in chronic lymphocytic leukemia (CLL) has been modest to date. An increasing body of evidence indicates that impaired CART cell fitness is the predominant mechanism of the relative dysfunction in CLL. The immunosuppressive microenvironment in CLL is well known and in part may be related to the abundance of circulating extracellular vesicles (EVs) bearing immunomodulatory properties. We hypothesized that CLL-derived EVs contribute to CART cell dysfunction. In this study, we aimed to investigate the interaction between circulating EVs isolated from CLL patient plasma (designated as CLL-derived EVs) and CART19 cells. We enumerated and immunophenotyped circulating EVs from platelet free plasma in untreated patients with CLL. We determined their interaction with CART19 cells using second generation, 41BB co-stimulated, lentiviral transduced CART19 cells generated in the laboratory from normal donors (FMC63-41BBζ CART cells). Our findings indicate that CLL-derived EVs impair normal donor CART19 antigen-specific proliferation against the CD19+ mantle cell lymphoma cell line Jeko-1 (Figure 1A). Next, we characterized CLL-derived EVs using nanoscale flow cytometric analysis of surface proteins and compared to healthy controls. Although the total EV particle count was not different between CLL and healthy controls (Figure 1B), there were significantly higher PD-L1+ EVs in patients with CLL (Figure 1C). Based on these results, we sought to assess the physical interaction between CLL-derived EVs and CART cells from normal individuals. When CLL-derived EVs were co-cultured with CART19 and CLL B cells and imaged with super-resolution microscopy, EVs were localized at the T cell-tumor junction (Figure 1D). Furthermore, CLL-derived EVs are captured by T cells as indicated by a significant reduction in the absolute count of EVs when co-cultured with resting T cells (Figure 1E). Having demonstrated that 1) there is an excess of PD-L1+ EVs in patients with CLL (Figure 1C) and 2) CLL-derived EVs physically interact with CART cells (Figures 1D-E), we sought to establish their functional impact on CART19 cells. Here, CART19 cells were stimulated with irradiated CD19+ JeKo-1 cells at a 1:1 ratio in the presence of increasing concentrations of CLL-derived EVs. There was a significant upregulation of inhibitory receptors such as PD-1 and CTLA-4 on the T cells (Figure 1F). This is associated with a reduction in CART effector cytokines (i.e., TNFβ) at higher concentrations of EVs (Figure 1G), suggesting a state of exhaustion in activated CART19 cells in the presence of CLL-derived EVs. This was further supported by transcriptome interrogation of CART19 cells. Here, CART19 cells were stimulated via 24-hour co-culture with the irradiated CD19+ cell line JeKo-1, in the presence of CLL-derived EVs at ratios of 10:1 and 1:1 EV:CART19 and then isolated by magnetic sorting. RNA sequencing of these activated CART19 cells indicated a significant upregulation of AP-1 (FOS-JUN) and YY1 (Figures 1H), known critical pathways in inducing T cell exhaustion. Finally, to confirm the impact of CLL-derived EVs on CART19 functions in vivo, we used our xenograft model for relapsed mantle cell lymphoma. Here, immunocompromised NOD-SCID-ɣ-/- mice were engrafted with the CD19+ luciferase+ cell line JeKo-1 (1x106 cells I.V. via tail vein injection). Engraftment was confirmed through bioluminescent imaging and mice were randomized to treatment with 1) untreated, 2) CART19 cells, or 3) CART19 cells co-cultured ex vivo with CLL-derived EVs for six hours prior to injection. A single low dose of CAR19 (2.5x105) was injected, to induce relapse. Treatment with CART19 cells that were co-cultured ex vivo with CLL-derived EVs resulted in reduced anti-tumor activity compared to treatment with CART19 alone (Figure 1I). Our results indicate that CLL-derived EVs induce significant CART19 cell dysfunction in vitro and in vivo, through a direct interaction with CART cells resulting in a downstream alteration of their exhaustion pathways. These studies illuminate a novel way through which circulating and potentially systemic EVs can lead to CART cell dysfunction in CLL patients. Disclosures Cox: Humanigen: Patents & Royalties. Sakemura:Humanigen: Patents & Royalties. Parikh:Ascentage Pharma: Research Funding; Janssen: Research Funding; AstraZeneca: Honoraria, Research Funding; Genentech: Honoraria; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; AbbVie: Honoraria, Research Funding; Acerta Pharma: Research Funding. Kay:Agios: Other: DSMB; Celgene: Other: Data Safety Monitoring Board; Infinity Pharmaceuticals: Other: DSMB; MorphoSys: Other: Data Safety Monitoring Board. Kenderian:Humanigen: Other: Scientific advisory board , Patents & Royalties, Research Funding; Lentigen: Research Funding; Novartis: Patents & Royalties, Research Funding; Tolero: Research Funding; Morphosys: Research Funding; Kite/Gilead: Research Funding.

Abstract Glioblastoma (GBM) is the most common and lethal primary brain tumor, and novel therapeutic strategies that make a substantial impact on outcomes are sorely needed. Immunotherapies have shown great promise in the treatment of a number of cancers in recent year, and a concerted effort is being made to apply these treatment paradigms to GBM. However, many GBM patients exhibit profound immunosuppression, likely limiting the efficacy of such approaches. The mechanisms of this immunosuppression are poorly understood, but tumor-derived extracellular vesicles (EVs), may play a role. We demonstrate that GBM-derived EVs induce the development of myeloid-derived suppressor cells (MDSCs) and non-classical monocytes (NCMs). We further demonstrate that these EV-induced monocytic cells are immunosuppressive, resulting in impaired T cell proliferation upon co-culture. We found that the immunosuppressive effects of tumor-derived EVs appear to be driven by the induction of these immunosuppressive monocytes, as EV treatment of T cells did not significantly impact T cell proliferation. Further, we sought to characterize the important of programmed death ligand 1 (PD-L1) in the induction of these immunosuppressive monocyte populations. We found PD-L1 to be expressed in the EVs from GBM cell lines, and that modulation in PD-L1 expression via either constitutive overexpression or shRNA-mediated knockdown resulted in concordant changes in expression in tumor-derived EVs. We demonstrate that PD-L1 is important for the induction of NCM but not for MDSCs. Taken together, these findings point to a significant role for tumor-derived EVs in the induction of immunosuppressive monocytes in GBM, and that these cells may be a driving force of systemic immunosuppression. PD-L1 is one factor expressed in EVs that has immunomodulatory properties, but additional EV cargo likely plays a major role in the induction of immunosuppressive cells.

Abstract BACKGROUND Diffuse intrinsic pontine gliomas (DIPG), known today as diffuse midline gliomas with the H3K27M mutation, are inoperable and aggressive brain tumors found predominantly in children. Despite extensive research no treatment or cure has been elucidated. Studies in 2012 showed that the majority of DIPG tumors have the H3K27M mutation, but the development of novel therapeutics has been hindered by lack of good laboratory models. Although patient derived cell lines with the H3K27M mutation have increased, the development of good murine xenografts are lagging, requiring extensive time and money. Previous studies have shown that the chicken embryo Chorioallantoic Membrane (CAM) model is an affordable and time-efficient method of studying tumor biology and response to treatment. We sought to develop this in H3K27M tumors to bridge the gap between in vitro—in vivo studies. METHODS Three patient-derived H3K27M cell lines were cultured and implanted on the chick embryo CAM on day 9 post-fertilization. Tumors underwent multiple drug treatment with 0.5uM or 2.0uM Alisertib (days 11, 13, 15) or a single targeted radiation treatment at 2 Grey (day 13). Tumor volume was assessed via ultrasound on day 16. The tumor specimens were harvested and analyzed by immunohistochemistry. RESULTS Patient-derived DIPG cells implanted on the CAM maintain their molecular characteristics and form tumors on the surface of the CAM as evidenced by H&E and H3K27M status. Statistically significant differences in volume were found in three H3K27M DIPG lines in Alisertib treated tumors compared to the control (p< 0.001, p< 0.001, p= 0.005). Statistically significant differences in tumor volume were found when treating two DIPG lines with targeted radiation therapy compared to controls (p= 0.01, p= 0.02). CONCLUSIONS These results validated the CAM assay as a reliable xenograft model for studying DIPG tumor biology and determining efficacy of drug and radiation treatment.

Abstract Introduction: Unprecedented clinical outcomes were reported after CD19 chimeric antigen receptor T cell (CART19) therapy and led to their FDA approval in diffuse large B cell lymphoma and in acute lymphoblastic leukemia. However, the complete response rate in chronic lymphocytic leukemia (CLL) after CART19 therapy is much lower, at approximately 20-30%, and the mechanism(s) for this relative lack of success is unclear. The dominant known mechanism(s) that prevent successful CART cell therapy in CLL have been limited to CART expansion and poor persistence. However, potential mechanisms are not limited to the CLL T-cell. Several immune defects have been identified in CLL that result from the complex bi-directional interaction between B-CLL cells and their microenvironment. In CLL the leukemic microenvironment is rich with extracellular vesicles (EVs) secreted by B-CLL cells. There is growing evidence that these vesicles play an important role in intracellular communication by the delivery of growth factors, genetic material and microenvironmentally relevant molecules. Therefore, we aimed to investigate the role and interactions of EVs in the diminished or absent CART response seen in some CLL patients. Methods: EVs were isolated from peripheral blood of 16 patients with untreated CLL at different Rai stages (8 patients had early and 8 had advanced stage disease) and risk profile by FISH (8 patients had low risk and 8 patients had high risk disease, based on the presence of 17p deletion). Cytometry was used to determine size, number of particles per µl, Annexin V and CD19 expression. These variables were correlated to the Rai stage and risk category of the disease. To investigate the impact of EVs on CART cell functions, CART19 cells were stimulated with either CLL EVs alone or in combination with the CD19 positive cell line JeKo1. After coincubation different effector functions were analysed. Results: Two patterns of EVs in CLL patients were identified; a single versus two distinct EV size populations (small [EVssmall]; 50-240nm, median=110nm) and large [EVslarge]; 180-560nm, median = 360nm Fig 1.A). In 25% of patients, EVs were CD19 positive (EVCD19+). CD19 positivity was detected only in patients with the EVslarge (Fig 1.B). The EVs concentration, CD19 expression (EVsCD19+ vs EVsCD19-), or the size (EVssmall vs EVslarge) did not correlate with disease stage (early vs advanced Rai stage) or risk profile of CLL (low vs high risk) although some variation could be seen (Fig 1.C). To investigate our hypothesis that EVs could modulate CART19 function, CART19 cell effector functions were examined in the presence of EVsCD19+, EVsCD19-, EVssmall, or EVslarge. EVs, 1.5x10e5 particles, alone were insufficient to stimulate CART19 cells. However when CART19 cells were stimulated with the CD19 positive cell line JeKo1, their effector functions were reduced only in the presence of EVsCD19+, 50,000 particles, 2.5 x 10e3/ µl, but not EVsCD19- at the same concentration. This included a significant reduction in CART specific killing (Fig 1.D) and a reduction in cytokine production. The impairment of CART cell functions was independent of the size of EVs, i.e. there was no impairment of CART functions with large or small size EVCD19- in co-culture. Summary: We identify CD19 positive large size EVs from patients with CLL and demonstrate that these EVs play a role in the leukemic microenvironment by reducing CART cell activity. Studies are ongoing to define the mechanism(s). Disclosures Parikh: Janssen: Research Funding; AstraZeneca: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding; Gilead: Honoraria; MorphoSys: Research Funding; Abbvie: Honoraria, Research Funding. Kay:Cytomx Therapeutics: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Research Funding; Infinity Pharm: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; Tolero Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees. Kenderian:Tolero Pharmaceuticals: Research Funding; Humanigen: Research Funding; Novartis: Patents & Royalties.