ANGI-03. TARGETING ANGIOGENIC PATHWAYS IN COMBINATION WITH OHSV THERAPY IN GBM

Glioblastoma (GBM) is the most aggressive brain malignancy, which despite continuing worldwide efforts to develop new therapies, remains a deadly disease with limited treatment options. The asparagine hydroxylase factor inhibiting HIF (FIH1) is located in chromosome 10q24, a region often deleted in GBM, suggesting a tumor protective role. FIH1 has been implicated in GBM as an inhibitor of HIF1α-mediated transcription of VEGF-A, leading to decreased angiogenesis. We previously showed that oncolytic HSV (oHSV) infection reduces the expression FIH1 via a virus encoded miRNA. Furthermore, we have found that FIH1 also negatively regulates NOTCH signaling, which is elevated following oHSV treatment. Thus, we hypothesize that FIH1 reconstitution in tumors will block pro-tumorigenic NOTCH and HIF1α signaling. Using FIH1-overexpressing GBM cells we observed a reduction in vascular permeability, measured by intravital imaging, and decreased expression of angiogenesis markers. In vivo, combination of FIH1 overexpression with oHSV treatment resulted in enhanced survival in mice bearing intracranial GBM tumors. Furthermore, FIH1 overexpression correlated with the enrichment of genes associated with oxidative phosphorylation and ROS pathways, suggesting the potential for multi-modality therapeutic strategies.

EXTH-42. DUAL ROLES OF PKR ORCHESTRATE ONCOLYTIC HSV SENSITIVITY AND ANTIGEN-SPECIFIC T CELL EXPANSION

The host immune system has developed many mechanisms to defend against and clear virus infections, including PKR, cGAS-STING and TLR-MyD88 signaling pathways. Compromised anti-viral mechanisms in tumor cells allows for infection, replication and lysis by oncolytic viruses. However, compromised antiviral mechanisms, together with immune cells and the tumor microenvironment (TME), limit the sensitivity of oncolytic virus in tumor cells. We generated a novel oncolytic Herpes simplex virus, oHSV-shPKR which disables tumor-intrinsic PKR signaling. oHSV-shPKR significantly increases oHSV infection and lysis in both oncolytic virus-resistant and sensitive glioblastomas (GBMs). Infection of oHSV-shPKR in GBMs induces G2/M cell cycle arrest and inhibits tumor cell growth. oHSV-shPKR increases activation of antigen presentation cells through type I interferon signaling activation and its immune-stimulatory function to increase tumor-antigen specific CD8 T-cell expansion, including cytotoxic T lymphocytes. Preclinical studies showed that oHSV-shPKR intra-tumoral injection significantly inhibits human GBM patient derived xenograft (PDX) tumor growth in immune-deficient NSG mice and murine orthotopic GBM tumor growth in immunocompetent mice. The results demonstrate that the novel oHSV-shPKR has the potential to be used in clinical applications for both oHSV-resistant and sensitive GBM treatment.

TMIC-39. TARGETING EXTRACELLULAR MATRIX HYALURONIC ACID-CD44 SIGNALING REDUCES TUMOR STEMNESS AND SENSITIZES TUMOR TO VIROTHERAPY AND ENHANCES THERAPEUTIC POTENTIAL FOR CANCER TREATMENT

The tumor microenvironment (TME), including the non-tumor cells and the extracellular matrix (ECM) plays a crucial role in tumor progression and metastasis. Hyaluronic acid (HA), the major glycosaminoglycan present in brain ECM, has long been associated with the progression and invasiveness of brain tumors. HA signals primarily thorough CD44, an adhesion/homing receptor leading to the induction of cellular AKT, MEK and HIF signaling, thereby promoting tumor cell proliferation, aggressiveness and therapy resistance. While HA in the ECM has been shown to interfere with infection and spread of oncolytic viruses, the impact of tumor-ECM interaction induced signaling on oncolytic virotherapy is heavily understudied. RNA sequencing and gene set enrichment analysis of glioma cells infected with an oncolytic Herpes Simplex Virus-1 (oHSV) demonstrate an enrichment of pathways related to tumor-ECM interaction. Immunostaining of brain sections from intracranial tumor bearing mice also reveals increased HA after oHSV treatment. Our results further demonstrate that HA/CD44-mediated signaling inhibits virus replication in vitro. Herein, to evaluate the impact of blocking tumor-ECM interactions without altering the secreted ECM, we created oHSV-sCD44, an oHSV that encodes for extracellular soluble CD44 (sCD44) that can function as a dominant negative receptor for membrane bound CD44. oHSV-sCD44 significantly reduces the stemness of glioblastoma stem cells (GSCs), induces DNA damage and sensitizes the GSCs to radiation therapy. Intra-tumoral injection of oHSV-sCD44 into patient-derived primary GBM xenograft model significantly inhibits tumor growth accompanied by reduced stemness and decreased HA expression, and increased oHSV replication and tumor cell lysis in TME. Moreover, blocking HA-CD44 signaling with a single dose of oHSV-sCD44 in murine glioma syngeneic model induces the development of a significant anti-tumor immune response with enhanced T cell infiltration. Collectively, our findings implicate oHSV-sCD44 as a potential oncolytic and immune-stimulating anticancer therapeutic.