Upregulation of MAGE-A1, MAGE-A3, NY-ESO-1 and MHC Molecules on Neuroblastoma Cells Following Exposure to Decitabine and Interferon-γ

Abstract 5179

MAGE-A1, MAGE-A3, and NY-ESO-1 are cancer-testis (CT) antigens expressed on a number of malignant solid tumors, including neuroblastoma (NB), but many tumor cell lines down-regulate the expression of CT antigens as well as major histocompatibility (MHC) antigens, precluding recognition by antigen specific T cells. If expression of cancer antigens as well as MHC molecules could be enhanced pharmacologically, the efficacy of CT antigen specific immunotherapy could be improved. DNA methylation is an epigenetic mechanism used by cells to decrease the expression of several genes, including tumor suppressor genes. Decitabine (5-aza-2′-deoxycytidine, DAC) is a potent inhibitor of DNA methylation, and the doses associated with the demethylating action of this drug are much lower than those required for cytotoxicit. We have demonstrated that the expression of MAGE-A1, MAGE-A3, and NY-ESO-1 can be upregulated on neuroblastoma cells following exposure to the DAC. When these cell lines are cultured in the presence of DAC at concentrations similar to levels achieved with clinical administration, we were able to achieve expression of NY-ESO-1, MAGE-A1, or MAGE-A3 in 11/11 neuroblastoma cell lines. Concentrations of 1uM DAC were associated with strongest expression of these antigens, which was optimal after 72 hours of drug exposure. Culture of NB cell lines with IFN-γ was also associated with an increased expression of either MHC Class I or II by cytofluorometry, and Class I upregulated in 10/11 of these cell lines, although to varying degrees. MAGE-A1, MAGE-A3, and NY-ESO-1 specific CTL were cultured from volunteer donors by stimulating peripheral blood mononuclear cells with dendritic cells pulsed with overlapping peptide mixes derived from full length proteins, and these CTL lysed HLA partially matched, DAC treated neuroblastoma as well as glioblastoma cell lines. These studies confirm that DAC and IFN-γ can be used to increase the expression of CT antigens and MHC molecules on neuroblastoma cells, and pre-treatment with these agents makes tumor cell lines more susceptible to CTL mediated killing.