Abstract 20: GIST-specific markers identified by comprehensive gene expression profiles.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm of the gastrointestinal tract and highly express c-kit. Although surgical removal and molecularly targeted therapy are known to be effective, specific markers other than c-kit would be beneficial for histopathological classification, risk assessment, and treatment decision. To this end, we conducted a DNA-microarry analysis using approximately 900 tumor tissues obtained in Fukushima Medical University Hospital from 2007 to present. The database contained more than 30 kinds of tumors including 10 cases of GIST. We searched ∼32,000 genes on the array that showed expression ratio of >2.0 in GIST samples compared to others, and finally extracted 54 GIST-specific genes. In this study, we identified that cathepsin L mRNA is highly expressed in GISTs. Moreover, immunohistochemical analysis of 43 GIST specimens revealed that 86.0% (n = 37) were cathepsin-L positive, and this positivity was significantly correlated with c-kit positivity. From these results, we conclude that cathepsin L is highly expressed in GISTs. Citation Format: Manabu Iwadate, Kohtaro Miyamoto, Emi Ito, Jun-ichi Imai, Naoki Sawada, Izumi Nakamura, Shinji Ohki, Shinya Watanabe, Satoshi Waguri, Seiichi Takenoshita. GIST-specific markers identified by comprehensive gene expression profiles. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 20. doi:10.1158/1538-7445.AM2013-20