Sunitinib mesylate inhibits proliferation of human colonic stromal fibroblasts in vitro and in vivo

Objective: Cancer stromal fibroblasts are important members of the cancer microenvironment. In this study, we determined the effect of sunitinib, a small molecule tyrosine kinase inhibitor, on the primary human colonic fibroblasts. Methods: Cell cycle analysis and cell proliferation assays were performed to evaluate the inhibitory effect of sunitinib in vitro. Western-blot analysis was performed to evaluate variations in the levels of phosphorylated platelet-derived growth factor receptor β (PDGFR-β), Akt, and ERK proteins. Co-injection of SW620 cells and colonic fibroblasts in nude mice was employed to test anti-growth efficacy in vivo. Results: Sunitinib was found to effectively inhibit the growth of primary colonic fibroblasts. Low-dose sunitinib blocked the PDGF-BB-induced cell proliferation and PDGFR-β signaling. Co-injection of SW620 cells and colonic fibroblasts in nude mice generated greater tumor volumes than single injection of SW620 cells. Sunitinib treatment inhibited the SW620 cell+colonic fibroblast tumor growth more effectively than treatment of 5-fluorouracil. Conclusions: Sunitinib mesylate inhibited the proliferation of primary human colonic fibroblasts through target-inhibited PDGFR signaling in vitro and in vivo.