Updated project metadata. The hypomethylating agent 5-azacytidine (AZA) is the first-line induction therapy for AML patients unsuitable for intensive chemotherapy. The anti-tumor effect of AZA results in part from T-cell cytotoxic responses against MHC-I-associated peptides (MAPs) deriving from hypermethylated genomic regions such as cancer-testis antigens (CTAs), or endogenous retroelements (EREs). However, clear evidence supporting higher ERE MAPs presentation after AZA treatment in AML is lacking. Therefore, we examined the immunopeptidome of four AML cell lines treated with AZA through a proteogenomic approach to validate this hypothesis.