ABSTRACT
PURPOSE: MAGE (melanoma antigen gene) is a tumor associated antigen, presented by HLA class I molecules, which is recognized by cytotoxic T lymphocytes. The expression of MAGE proteins are confined to malignant tumor tissues, except for the normal testis and placental tissues. Therefore, MAGE may be a potential target for immunotherapy of malignant tumors. However, biological aspects associated with the cell cycle are not yet described. MATERIALS AND METHODS: The material used for this study was a novel human squamous cell carcinoma cell line (PNUH-12) from the hypopharynx, which had one point mutation of 78th base, C to G, in exon 7 of p53 gene. To understand the role of MAGE in relation to cell cycle and its relationship with p53 as the Gl checkpoint regulator, the expressions of MAGE-3 protein and mvtant p53 (Mtp53) were accessed by flow cytometry and immunohistochemistry. Double stains for MAGE-3/Mtp53 was analyzed with bivariate flow cytometry. DNA histograms using MAGE-3/PI (DNA) and Mtp53/PI (DNA) were also analyzed. RESULTS: The expression rate of MAGE-3 and Mtp53 were 83% and 85%, respectively. MAGE-3 was expressed in cytoplasm, while M:p53 were expressed in the nuclei of the tumor cells on the immunohistochemical sections. With bivariate analyses, coexpression rate of MAGE-3/Mtp53 was 0.96, and MAGE-3 and Mtp53 constantly showed high levels throughout the cell cycle except Go. CONCLUSIONS: These results mean that (I) MAGE-3 might have yet unknown relationship with mutant p53, (2) expressions of MAGE-3 and Mtp53 are not dependent on the cell cycle in PNUH-12 hypopharyngeal squamous carcinoma cell line, and suggest that MAGE-3 might have a role as important as p53 during the development of malignant tumors.