Identification of Novel Transmembrane Proteins in Scirrhous-Type Gastric Cancer by the Escherichia coli Ampicillin Secretion Trap (CAST) Method: TM9SF3 Participates in Tumor Invasion and Serves as a Prognostic Factor

Objective: Scirrhous-type gastric cancer (GC) is highly aggressive and has a poor prognosis due to rapid cancer cell infiltration accompanied by extensive stromal fibrosis. The aim of this study is to identify genes that encode transmembrane proteins frequently expressed in scirrhous-type GC. Methods: We compared Escherichia coli ampicillin secretion trap (CAST) libraries from 2 human scirrhous-type GC tissues with a normal stomach CAST library. By sequencing 2,880 colonies from scirrhous CAST libraries, we identified a list of candidate genes. Results: We focused on the TM9SF3 gene because it has the highest clone count, and immunohistochemical analysis demonstrated that 46 (50%) of 91 GC cases were positive for TM9SF3, which was observed frequently in scirrhous-type GC. TM9SF3 expression showed a significant correlation with the depth of invasion, tumor stage and unReceived: November 7, 2013 Accepted after revision: December 9, 2013 Published online: March 8, 2014 Wataru Yasui Department of Molecular Pathology Hiroshima University Institute of Biomedical and Health Sciences 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551 (Japan) E-Mail wyasui @ hiroshima-u.ac.jp © 2014 S. Karger AG, Basel 1015–2008/14/0813–0138$39.50/0