We aimed to determine the effect of SGI-110 on methylation and expression of the cancer testis antigens (CTAs) NY-ESO-1 and MAGE-A in epithelial ovarian cancer (EOC) cells in vitro and in vivo and to establish the impact of SGI-110 on expression of major histocompatibility (MHC) class I and Intracellular Adhesion Molecule 1 (ICAM-1) on EOC cells, and on recognition of EOC cells by NY-ESO-1-specific CD8+ T-cells. We also tested the impact of combined SGI-110 and NY-ESO-1-specific CD8+ T-cells on tumor growth and/or murine survival in a xenograft setting. EOC cells were treated with SGI-110 in vitro at various concentrations and as tumor xenografts with 3 distinct dose schedules. Effects on global methylation (using LINE-1), NY-ESO-1 and MAGE-A methylation, mRNA, and protein expression were determined and compared to controls. SGI-110 treated EOC cells were evaluated for expression of immune-modulatory genes using flow cytometry, and were co-cultured with NY-ESO-1 specific T-cell clones to determine immune recognition. In vivo administration of SGI-110 and CD8+ T-cells was performed to determine anti-tumor effects on EOC xenografts. SGI-110 treatment induced hypomethylation and CTA gene expression in a dose dependent manner both in vitro and in vivo, at levels generally superior to azacitidine or decitabine. SGI-110 enhanced the expression of MHC I and ICAM-1, and enhanced recognition of EOC cells by NY-ESO-1-specific CD8+ T-cells. Sequential SGI-110 and antigen-specific CD8+ cell treatment restricted EOC tumor growth and enhanced survival in a xenograft setting. SGI-110 is an effective hypomethylating agent and immune modulator and, thus, an attractive candidate for combination with CTA-directed vaccines in EOC.
Keywords: AZA, Azacitidine (5-azacytidine); CTA, Cancer-testis antigen or cancer-germline antigen; CTAG1B, Cancer/testis antigen 1B; DAC, Decitabine (5-aza-2′-deoxycitidine); DNA methylation; DNA methyltransferase inhibitors; DNA, Deoxyribonucleic acid; DNMTi, DNA methyltransferase inhibitor; EOC, Epithelial ovarian cancer; HLA, Human leukocyte antigen; ICAM-1, Intracellular Adhesion Molecule 1; LINE-1, Long interspersed nuclear element-1; MAGE-A, Melanoma antigen family A; MHC, Major histocompatibility complex; NY-ESO-1, New york esophageal squamous cell carcinoma 1; RNA, Ribonucleic acid; SGI-110; cancer germline genes; cancer testis antigens; epigenetics; epithelial ovarian cancer; immune modulation.