Expression of MAGE-antigens in normal tissues and cancer

The human MAGE gene family encodes products that can be recognized by autologous cytotoxic T cells. Because MAGE genes are silent in most normal tissues except testis but are activated in a variety of neoplastic lesions, MAGE antigens represent ideal targets for immunotherapy. Current knowledge of MAGE gene expression is based primarily on mRNA typing and relatively little is known about MAGE protein expression. Monoclonal antibody (MAb) 57B, originally thought to be specific for MAGE-3, but now known to be reactive with other MAGE components, was used in the present study to analyze MAGE expression in a panel of normal and malignant tissues. In tests with a wide range of normal tissues, only spermatogenic cells of testis were reactive with 57B. In tumor tissues, significant immunoreactivity was observed in malignant melanomas and carcinomas of the lung, head and neck as well as urinary bladder. No 57B reactivity was seen with colorectal, prostatic or renal cell carcinomas. Lipo- and myosarcomas, as well as malignant fibrous histiocytoma (MFH), were negative, but synovial sarcomas showed intense immunoreactivity. A subset of seminomas was also strongly reactive with 57B. Tumor specimens showed great variability in the number of tumor cells showing 57B reactivity, with some tumors showing only small isolated clusters of positive cells to other tumors with uniform staining throughout the tumor.