Melanoma-Associated Antigens in Esophageal Adenocarcinoma

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Abstract
Purpose: The melanoma-associated antigens (MAGEs) are tumor-specific antigens recognized by cytotoxic T lymphocytes. In this study, expression of MAGE family A members was evaluated during the development of esophageal adenocarcinoma (EA) as potential targets for immunotherapy. Experimental Design: MAGE-A mRNA expression was evaluated in 46 samples including Barrett’s metaplasia (BM), dysplasia, and EA using oligonucleotide microarrays. Expression of MAGE-A proteins was confirmed by immunohistochemistry on tissue microarrays containing 59 EA, 11 dysplasia, and 9 BM samples and by Western blot. To further evaluate MAGE-A10 expression, reverse transcription-polymerase chain reaction (RT-PCR) products were sequenced, and protein expression was determined using a specific antibody. Results: Overexpression of MAGE-A1, MAGE-A2b, MAGE-A3, MAGE-A4, MAGE-A6, MAGE-A9, MAGE-A10, and MAGE-A12 was found in EAs relative to BM on oligonucleotide microarrays. MAGE-A3 overexpression was confirmed by real-time RT-PCR in 21.4% (6 of 28) of esophageal tumors. Immunohistochemistry on tissue microarray revealed MAGE-A proteins in 20.3% (12 of 59) of EAs and MAGE-A10 staining in 16.9% (10 of 59) of EAs. MAGE-A expression was confirmed by Western blot in several esophageal tumors and in two EA cell lines, Flo-1 and Seg-1, whereas Flo-1 also expressed MAGE-A10. Tumors produced from these cell lines in nude mice retained MAGE-A expression. Interestingly, RT-PCR in primary tumors expressing MAGE-A10 protein revealed additional PCR products that were identified as novel MAGE-A10 alternative splice variants using DNA sequencing. Conclusions: This is the first report of these MAGE-A10 alternative splice sequences, and characterization of MAGE-A expression may provide potential targets for immunotherapy in patients with EA.