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

Abstract

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 "Metaddicted" 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 anchorageindependent 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. ©2010 AACR.

Rack1 promotes epithelial cell–cell adhesion by regulating E-cadherin endocytosis

“…Src is both a downstream effector and activator of c-Met signaling (Herynk et al, 2007;Emaduddin et al, 2008;Fan et al, 2009;Leroy et al, 2009;Bertotti et al, 2010). Thus, our findings that Rack1, partly by inhibiting Src, promotes E-cadherin-dependent cell-cell adhesion (Figure 1b), inhibits matrigel invasion (Figures 1c and d) and regulates E-cadherin endocytosis (Figure 4), prompted us to assess Rack1's influence on HGFstimulated cell scatter and E-cadherin endocytosis.…”

A phase II trial of the Src kinase inhibitor saracatinib (AZD0530) in patients with metastatic or locally advanced gastric or gastro esophageal junction (GEJ) adenocarcinoma: a trial of the PMH phase II consortium

“…[16]. A second pre clinical paper demonstrates anti cancer activity for saracatinib in gastric carcinoma cell lines dependent on c Met for growth [24]. The authors suggest whilst the treatment of MET-amplified, Metaddicted tumors with Met inhibitors might be the goal the use of compounds such as saracatinib which blocks a Metdependent signal might increase efficacy and minimize side effects.…”

MET signalling: principles and functions in development, organ regeneration and cancer

“…In a limited number of tumour cells featuring genetic lesions of MET -caused by gene amplification and, possibly, point mutations 23,140,141 -receptor hyperactivation is inherent in the cancer's natural history and is required to maintain the transformed phenotype: these cells are dependent on the persistent activity of MET for their relentless proliferation (a situation known as 'oncogene addiction') 142,143 . In this scenario, MET blockade affects a limited subset of MET downstream signals: many of the pathways controlling MET-driven responses -including STATs, JNK, p38 and NF-κB -remain active or exhibit scant responses, and only a restricted complement of Ras and PI3K transducers and transcriptional effectors is neutralized 144,145,146 . Of note, a similar response to oncogene inactivation also occurs in cells that depend on the EGF receptor for their growth and survival, suggesting that cells that are 'addicted' to oncogenic tyrosine kinase receptors may develop common mechanisms to sustain malignancy and therefore may be susceptible to similar therapeutic interventions 144,145 .…”