Abstract 518: Immunogenicity of cancer/testis antigen <i>XAGE-1d</i> in patients with non-small cell lung cancer (NSCLC)
Authors: Hirofumi Matsumoto, Yoshihiro Ohue, Shingo Eikawa, Yu Mizote, Koji Kurose, Midori Isobe, Akiko Uenaka, Takeshi Nagayasu, Mikio Oka, Eiichi Nakayama
Journal: Cancer Research (2012)

Abstract BACKGROUND: Cancer/testis (CT) antigens expresses in various cancers and normal testis. Because of no expression of HLA class-I antigen in normal testis, CT antigens are promising molecular target for specific cancer immunotherapy. XAGE-1 gene has been identified as a CT-like antigen, and XAGE-1 gene has four alternative splice variants: XAGE-1a, XAGE-1b, XAGE-1c, and XAGE-1d. We previously reported that the transcript of XAGE-1a and XAGE-1b coded the same protein (GAGED2, isoform a, 81 amino acids) and the transcript of XAGE-1d coded another protein (GAGED2, isoform b, 69 amino acids). The first half of XAGE-1b and 1d protein (1-32 amino acids) is same sequence. On the other hand, XAGE-1c transcript codes some peptides but not a protein. Previously, immunogenic analyses of XAGE-1b have been performed because of its dominant expression, however, few analysis of XAGE-1d was performed. In this study, we investigated the immunogenicity of XAGE-1d in patients with non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Tumor tissue samples for extracting mRNA were obtained from NSCLC patients treated surgical resection at Nagasaki University Hospital during the period from 2005 to 2010. Sera and PBMCs were obtained from NSCLC patients who visited Kawasaki Medical School Hospital during the period from 2005 to 2010. Splising variants of XAGE-1 gene were analyzed by quantitative real-time PCR with specific TaqMan probe-primer sets. Antibody responses to XAGE-1d were analyzed by ELISA using synthesized XAGE-1b protein. In antibody-positive patients, CD4+ T-cell responses against XAGE-1d were examined by IFN-γ ELISA. Epitope-peptides recognized by XAGE-1d specific T-cells were determined by ELISA using XAGE-1d-overlapping peptides (OLPs). RESULTS: In quantitative real-time PCR, expression of XAGE-1d mRNA was observed in 16/38 specimens (42.1%) that were also positive with XAGE-1b mRNA. The correlation coefficiency of the expression was 0.8047. Protein expression of XAGE-1d was observed in cytoplasm, being different from that of XAGE-1b in the nucleus in lung cancer cell lines by immunohistochemical staining. Antibody against XAGE-1d was detected in lung cancer patients who were also positive with XAGE-1b antibody. By a limiting dilution, a CD4+ T-cell clone was obtained from PBMCs in a seropositive patient. HLA class II restricted recognition of XAGE-1d was confirmed using various allogeneic EBV-B cells as APC. 14-mer minimal epitope peptide was determined. CONCLUSION: The findings indicate that XAGE-1d co-expresses with XAGE-1b and is immunogenic in NSCLC patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 518. doi:1538-7445.AM2012-518