Rexpression of HLA class I antigens and restoration of antigen-specific CTL response in melanoma cells following 5-aza-2'-deoxycytidine treatment

Int J Cancer. 2001 Oct 15;94(2):243-51. doi: 10.1002/ijc.1452.


Cell surface expression of HLA class I/peptide complexes on tumor cells is a key step in the generation of T-cell-based immune responses. Several genetic defects underlying the lack of HLA class I expression have been characterized. Here we describe another molecular mechanism that accounts for the complete absence of HLA class I molecule expression in a tumor line (MSR3-mel) derived from a melanoma patient. Hypermethylation of the MSR3-mel DNA, specifically of HLA-A and -B genes, was identified, which resulted in loss of HLA class I heavy chain transcription. Treatment of MSR3-mel cells with the demethylating agent 5'-aza-2'-deoxycytidine (DAC) allowed HLA-A and -B transcription, restoring cell surface expression of HLA class I antigens and tumor cell recognition by MAGE-specific cytotoxic T lymphocytes. The MSR3-mel line was obtained from a metastatic lesion of a nonresponding patient undergoing MAGE-3.A1 T-cell-based peptide immunotherapy. It is tempting to speculate that the hypermethylation-induced lack of HLA class I expression is the cause of the impaired response to vaccination. This study provides the first evidence that DNA hypermethylation is used by human neoplastic cells to switch off HLA class I genes, thus providing a new route of escape from immune recognition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antimetabolites, Antineoplastic / therapeutic use*
  • Azacitidine / analogs & derivatives
  • Azacitidine / therapeutic use*
  • DNA Methylation*
  • Decitabine
  • Epitopes, T-Lymphocyte
  • Genes, MHC Class I*
  • HLA-A Antigens / genetics
  • HLA-B Antigens / genetics
  • Humans
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Melanoma / immunology
  • T-Lymphocytes, Cytotoxic / immunology*
  • Tumor Cells, Cultured


  • Antimetabolites, Antineoplastic
  • Epitopes, T-Lymphocyte
  • HLA-A Antigens
  • HLA-B Antigens
  • Decitabine
  • Azacitidine