The DNA demethylating agent 5-aza-2'-deoxycytidine induces expression of NY-ESO-1 and other cancer/testis antigens in myeloid leukemia cells.

Azanucleoside DNA-hypomethylating agents have remarkable clinical activity in myelodysplastic syndromes and acute myeloid leukemia (AML), particularly at low, non-cytotoxic doses favoring hypomethylation over cytotoxicity. Cancer/testis antigens (CTAs) encoding immunogenic proteins are not expressed in almost all normal tissues and many tumor types, but are consistently derepressed by epigenetically active agents in various cancer cell lines. Since the expression of CTA genes is usually very low or absent in myeloid leukemias, we treated various AML cell lines with 5-aza-2'-deoxycytidine (DAC) and quantified mRNA expression of the CTAs NY-ESO-1, MAGEA1, MAGEA3 and MAGEB2. Consistent time- and dose-dependent reactivation of all 4 CTA genes was observed, with maximum mRNA levels 72-144h after treatment start. As determined by RNA microarray analyses, numerous other CTA genes (all located on the X-chromosome) were also derepressed in a time-dependent fashion by DAC. NY-ESO-1 derepression was confirmed at the protein level. By Elispot and chromium release assays we showed that the de novo expressed NY-ESO-1 protein was naturally processed and presented in a time- and dose-dependent fashion up to 8 days after the start of DAC treatment, and converted the cell lines susceptible to antigen-specific recognition by CD8+ T-cell clones. In conclusion, NY-ESO-1 and numerous other CTAs localized on the X-chromosome are readily and transiently derepressed in AML cell lines treated with DAC. The susceptibility of DAC-treated AML cell lines to antigen-specific T-cell recognition has clear implications for future clinical trials combining DAC and specific immunotherapy in AML.