Functional Up-regulation of Human Leukocyte Antigen Class I Antigens Expression by 5-aza-2′-deoxycytidine in Cutaneous Melanoma: Immunotherapeutic Implications

Purpose: To investigate the potential of the DNA hypomethylating agent 5-aza-2′-deoxycytidine (5-aza-CdR) to improve the effectiveness of immunotherapeutic approaches against melanocyte differentiation antigens. Experimental Design: The effect of 5-aza-CdR on the constitutive expression of gp100 was investigated in 11 human melanoma cell lines by real-time reverse transcription-PCR and indirect immunofluorescence (IIF) analyses. 5-aza-CdR–mediated changes in the levels of expression of human leukocyte antigen (HLA) class I antigens and HLA-A2 allospecificity, intercellular adhesion molecule-1 (ICAM-1), and leukocyte-function–associated antigen-3 were investigated by IIF analysis on melanoma cells under study. The recognition of gp100-positive Mel 275 melanoma cells, treated or not with 5-aza-CdR, by HLA-A2–restricted gp100 (209–217) -specific CTL was investigated by 51 Cr-release assays, IFN-γ release and IFN-γ ELISPOT assays. Results: The constitutive expression of gp100 was not affected by 5-aza-CdR on all melanoma cells investigated. Compared with untreated cells, the exposure of Mel 275 melanoma cells to 5-aza-CdR significantly ( P < 0.05) up-regulated their expression of HLA class I antigens and of ICAM-1. These phenotypic changes significantly ( P < 0.05) increased the lysis of 5-aza-CdR–treated Mel 275 melanoma cells by gp100-specific CTL and increased their IFN-γ release. 5-aza-CdR treatment of Mel 275 cells also induced a higher number of gp100-specific CTL to secrete IFN-γ. Conclusions: Treatment with 5-aza-CdR improves the recognition of melanoma cells by gp100-specific CTL through the up-regulation of HLA class I antigens expression; ICAM-1 also contributes to this phenomenon. These findings highlight a broader range of therapeutic implications of 5-aza-CdR when used in association with active or adoptive immunotherapeutic approaches against a variety of melanoma-associated antigens.