Abstract 1244: Differential requirements for the receptor tyrosine kinase c-Met in scirrhous gastric carcinoma cell lines

Abstract

The prognosis of patients with scirrhous gastric carcinoma (SGC) has been very poor. SGC cells do not form obvious tumor mass, but cause diffuse infiltration and eventually rigid thickening of the gastric wall. Furthermore, SGC cells frequently infiltrate through gastric serosa and cause peritoneal dissemination. However, the mechanisms underlying the progression of SGC have not yet been fully elucidated. In the present study, we performed immunoblotting and proteomic analyses of tyrosine-phosphorylated proteins in differentiated non-SGC cell lines (MKN7, MKN1, and MKN74) and poorly differentiated or SGC cell lines (MKN45, NUGC-4, KATO III, HSC59, 58As9, HSC44-PE, and 44As3) to identify signaling pathways and molecules that are characteristics of SGC. We found that the tyrosine kinase receptor c-Met is overexpressed and highly phosphorylated in SGC cell lines. c-Met is a cell surface receptor for HGF and implicated in the growth, survival, invasion, and metastasis of various human cancers. Amplification of c-Met gene in SGC was also previously reported. We analyzed the downstream signaling pathways of c-Met in SGC cells by using two c-Met inhibitors PHA-665752 and JNJ-38877605. Treatment of 58As9 cells with the c-Met inhibitors markedly inhibited phosphorylation of Erk, Akt, and Stat3, but promoted phosphorylation of Src. In contrast, 44As3 cells treated with the c-Met inhibitors showed no significant changes in phosphorylation of these molecules, in spite of successful inhibition of c-Met phosphorylation. Reflecting these observations, c-Met inhibitors blocked cell proliferation and caused morphological alterations in 58As9 cells but not in 44As3 cells. Similar results were obtained when MKN45 and NUGC-4 cells were analyzed in the same manner: MKN45 cells but not NUGC-4 cells were sensitive to c-Met inhibition. These results suggest that SGC can be classified into two subtypes according to their dependencies on the c-Met signaling pathway. Further studies are now conducted to identify therapeutic targets in c-Met-independent SGC cell lines. 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 1244. doi:1538-7445.AM2012-1244