Role of FGFR2 and FGFR3 activation in association with invasion and tumorigenesis in gastric cancer

Abstract

Activation of fibroblast growth factor receptors (FGFRs), family of receptor tyrosine kinase (RTK), initiates intracellular signaling networks for key cellular processes. Mechanism of FGFRs has been studied in various cancers, but only FGFR2 related cell proliferation and survival has been reported in gastric cancer. In this study, we evaluated the activation level of FGFRs and its related downstream pathways. Also, we determined the effect of FGFRs in tumor invasion and tumorigenesis in gastric cancer. We performed phospho-RTK array for 25 gastric cancer cell lines and found that FGFR2 and FGFR3 were more frequently phosphorylated than FGFR1 and FGFR4 in gastric cancer. Then, we observed the status of genomic amplification and phosphorylation level using real-time PCR and immunoblot. FGFR2 was overexpressed in KATO III and SNU-16 and showed a high correlation between DNA amplification and phosphorylation status, while Hs746T and SNU-5 showed phosphorylated FGFR3 only. We selected 5 gastric cancer cell lines and grouped the following phosphorylation level of FGFRs; FGFR2 positive, FGFR3 positive, and negative control. For functional evaluation of FGFRs in selected gastric cancer cell lines, gene silencing experiment was conducted with siRNA transfection followed by cell proliferation assay, cell cycle analysis, apoptosis assay, invasion assay, and soft agar assay. In these in vitro experiments, we observed that inhibiting FGFRs delayed proliferation, induced cell cycle arrest and apoptosis, decreased invasion and colony formation; confirming that the downstream signaling molecules of FGFRs were repressed. Interestingly, FGFR2 and FGFR3 had some discrepancies in cell cycle and apoptosis, but other cellular mechanism and downstream signaling pathway of both FGFRs were similar. Through in vivo xenograft tumor model, we demonstrated that inhibiting FGFR3 significantly reduced tumorigenesis in gastric cancer cells compared to control group. Furthermore, we detected high expression of FGFR3 more frequently than FGFR2 in gastric cancer patient’s tissues of advanced stage. In conclusion, we suggest that FGFR2 and FGFR3 play biological roles through similar signaling pathways, and may act as the potential molecular targets in gastric cancer.