Inhibition of Src Impairs the Growth of Met-Addicted Gastric Tumors

Purpose: We examined whether inhibition of Src tyrosine kinase, a downstream effector of the MET oncogene, can hinder the malignant properties of gastric tumors dependent on Met for growth and survival. Experimental Design: Sensitivity to Src inhibition was determined in vitro by measuring clonogenic survival (anchorage-independent growth) and in vivo by establishing xenograft models. Four Met-addicted gastric carcinoma cell lines (GTL16, MKN45, HS746T, and SNU5) and three Met-independent gastric carcinoma cell lines (KATO III, AGS, and NCI-N87) were treated with the Src inhibitor saracatinib (AZD0530). In GTL16 and KATO III, Src neutralization was also achieved by dasatinib and RNA interference. The biochemical and transcriptional consequences of Src inhibition were explored using anti-phosphoprotein antibodies and oligonucleotide microarrays. Results: Inhibition of Src in Met-addicted gastric carcinoma cell lines (a) decreased the phosphorylation/activation levels of signaling intermediates involved in cell proliferation and protection from apoptosis and down-modulated the expression of several cell cycle regulators; (b) reduced anchorage-independent growth; (c) enhanced impairment of cell viability produced by Met inhibition; and (d) delayed tumorigenesis in xenotransplantation models. Immunohistochemical analysis of tumor xenograft tissues following systemic treatment with saracatinib showed a reduction of tumor cell proliferation index, increased apoptosis, and diminished phospho-focal adhesion kinase and phospho-paxillin staining. Tumor stroma parameters such as angiogenesis or inflammatory infiltration were unaffected. In clonogenic survival assays, gastric carcinoma cells without addiction to Met were less sensitive than Met-addicted cells to Src inhibition. Conclusions: Src is as a key downstream transducer of Met-driven tumor growth. Targeting Src might provide therapeutic benefit in Met-addicted tumors. Clin Cancer Res; 16(15); 3933-43. (C) 2010 AACR.