Abstract 5552: MAGE-A3 and MAGE-A4 protein show co-expression in tumor of lung, bladder, and colon cancer

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Abstract Melanoma Antigen Gene Family (MAGE-A) are part of the cancer-testis antigens whose limited expression in normal tissues and high expression in cancer make them excellent targets for immunotherapy. Clinical trials have already begun targeting MAGE-A3 and MAGE-A4 proteins in tumors. Should these trials lead to new treatment protocols, it is important to develop a diagnostic immunohistochemistry (IHC) tool for pre-screening patients who would benefit. The MAGE-A family consists of 12 members that share up to 85% sequence homology presenting a challenge for finding highly specific antibodies for IHC. Using CytoSections, a new screening control tool for IHC, ICC, IF, and in-situ hybridization, highly specific IHC MAGE-A3 and MAGE-A4 antibodies were developed and screened. The MAGE-A3 and MAGE-A4 antibodies were assessed on twenty-two lung cancers, twenty-one colon cancer, and more than thirty bladder cancers which resulted in cases that co-express MAGE-A3 and MAGE-A4 proteins in all three types of tumors. Using immunofluorescence, tumors positive for both proteins were double stained for MAGE-A3 and MAGE-A4 to show the proteins were co-expressed in the same tumor cells. Immunohistochemistry continues to be a rapid and reproducible method for the detection of proteins in tumors. Antibodies specific to MAGE-A3 and A4 proteins for IHC may be a useful tool in predicting outcomes or benefits for patients. Citation Format: Rachel Gonzalez. MAGE-A3 and MAGE-A4 protein show co-expression in tumor of lung, bladder, and colon cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5552.