Consistent with previous studies in breast cancer (10), colon cancer (10, 11), lung cancer (10, 29) and melanoma cell lines (11), radiation increased MHC-I expression in three out of the four mesothelioma cell lines studied, presenting a potential mechanism by which radiation can sensitize tumor cells to CD8+ T cell-mediated killing. This evidence concerns the gene CD8A and malignant colon neoplasm.