IMMU-30. NOVEL HYPOMETHYLATING AGENT GSK-3484862 SENSITIZES GLIOBLASTOMA TO NY-ESO-1 SPECIFIC IMMUNOTHERAPY

Abstract

Abstract INTROUCTION Immunotherapy is a promising mode of treatment due to its specificity and efficacy in eliminating tumors, but is limited in GBM due to the lack of immunogenicity and unique cancer antigen expression. Previous work from our group has shown that Decitabine (DAC), a demethylating agent, can improve the immunogenicity of Glioblastoma (GBM) for immuno-therapeutic targeting through the upregulation of immunogenic cancer testis antigens (CTA) such as NY-ESO-1 and altered expression of other immunoregulatory programs. However, immunosensitization using DAC is limited due to non-specific toxicity after prolonged administration. We hypothesize that a newly synthesized hypomethylating agent, GSK-3484862 (GSK), may be an effective alternative to DAC in promoting CTA expression in GBM with limited cytotoxic effects on surrounding immune cells. METHODS Human GBM cells and patient-derived glioma spheres were treated with GSK and DAC. We investigated the differential expression in NY-ESO-1 at a transcriptional level between DAC and GSK through quantitative real-time PCR. To assess whether these differences translated into heightened immune responses as a result of NY-ESO-1 upregulation, we co-cultured DAC and GSK-treated immortalized and primary cell lines with transduced NY-ESO-1 specific T-cell receptor T-cells. RESULTS Immortalized and primary glioma sphere cells demonstrated equivalent NY-ESO-1 gene upregulation after four days of treatment between 1 µM DAC and 5 µM GSK. Glioma spheres treated for three weeks at a dose of either 0.5 µM DAC or 2.5 µM GSK demonstrate equivalent NY-ESO-1 upregulation. Furthermore, xCELLigence data demonstrates that equivalent NY-ESO-1 expression achieved by the differential dosing between GSK and DAC leads to similar rates of NY-ESO-1 specific T-cell mediated killing, indicating a functional equivalence between GSK and DAC induced immunosensitization at equivalent NY-ESO-1 expression levels. CONCLUSION Our results demonstrate a preclinical rationale for the use of GSK as a viable pro-antigenic agent for the sensitization of GBM to targeted immune therapy.