EXPRESSION OF THE MAGE-1 TUMOR-ANTIGEN IS UP-REGULATED BY THE DEMETHYLATING AGENT 5-AZA-2'-DEOXYCYTIDINE

MAGE-1 is a gene that encodes an antigen on a melanoma cell line that is recognized by cytolytic T-cells. We have used a reverse transcripti on-polymerase chain reaction assay to analyze expression of the MAGE-1 gene by cell lines from different types of tumors, melanomas from dif ferent stages of disease progression, normal diploid cell lines, and m elanocyte and nevus tissue from which malignant melanomas are derived. MAGE-1 is expressed by melanoma tissue from all stages of disease, bu t not melanocytes, nevus tissue, or any normal diploid cell line teste d. A fraction of tumor lines derived from various epithelial and neuro ectodermal malignancies expressed MAGE-1 but not peripheral blood cell s from patients with melanoma. 5-Aza-2'-deoxycytidine (DAC), a demethy lating agent, was capable of inducing MAGE-1 expression by a MAGE-1-ne gative melanoma cell line 888-mel as well as by a number of other mela noma cell lines. At an optimum concentration of 1 muM DAC, MAGE-1 expr ession was detectable by 24 h, plateaued by 72 h, but remained high fo r two weeks after removal of DAC from treated 888-mel cells, consisten t with induction by demethylation. With the exception of tumor-infiltr ating leukocytes, no normal diploid cell line could be induced with DA C to up-regulate MAGE-1 expression. DAC-treated 888-mel cells were lys ed by a MAGE-1-specific major histocompatibility complex restricted cy tolytic T-cell clone, whereas control untreated cells were not, sugges ting that production of the antigen encoded by the MAGE-1 gene was ind uced by DAC and that it was presented in association with major histoc ompatibility complex class I molecules at the cell surface for T-cell recognition.