Saracatinib impairs the peritoneal dissemination of diffuse‐type gastric carcinoma cells resistant to M et and fibroblast growth factor receptor inhibitors

Diffuse‐type gastric carcinomas ( DGC ) exhibit more aggressive progression and poorer prognosis than intestinal‐type and other gastric carcinomas. To identify potential therapeutic targets, we examined protein tyrosine phosphorylation in a panel of DGC and other gastric cancer cell lines. Protein tyrosine phosphorylation was significantly enhanced or altered in DGC cell lines compared with that in other gastric cancer cell lines. Affinity purification and mass spectrometry analysis of tyrosine‐phosphorylated proteins identified M et as a protein that is preferentially expressed and phosphorylated in DGC cell lines. Unexpectedly, M et inhibitors blocked cell growth, M et downstream signaling and peritoneal dissemination in vivo in only a subset of cell lines that exhibited remarkable overexpression of M et. Likewise, only cell lines with overexpression of fibroblast growth factor receptor 2 ( FGFR 2) or phosphorylation of FRS 2 were sensitive to an FGFR 2 inhibitor. A S rc inhibitor saracatinib impaired growth in cell lines that are insensitive to both M et and FGFR 2 inhibitors. Saracatinib also effectively impaired peritoneal dissemination of M et‐independent and FGFR 2‐independent SGC cells. Moreover, DGC cell lines exhibited nearly mutually exclusive susceptibility to M et, FGFR and S rc inhibitors. These results suggest that DGC have distinct sensitivities to molecular target drugs and that targeting S rc is beneficial in the treatment of DGC insensitive to M et and FGFR inhibition.