Insulin enhanced KRAS-dependent migration and invasion via SSTR2/AKT axis

Abstract

Hyperinsulinemia has been reported to be a risk factor of pancreatic cancer, but the role and mechanism of insulin in carcinogenesis still remained unclarified. This study is to elucidate the synergistic effect of insulin in Kras-dependent tumorgenesis. 20nM was chosen as optimal concentration for insulin treatment after examining the effect of different concentrations of insulin in HPNE-mut-Kras and HPNE-E6E7 cell lines. Transwell, CCK8 and EDU assays showed that migration, invasion and proliferation capability of the two cell lines were significantly enhanced after insulin co-incubation. Digital gene expression (DGE) sequencing revealed that SSTR2 were downregulated in HPNE-mut-Kras but not in HPNE-E6E7, indicating that this gene might be inhibited by KRAS. Then, the expression of SSTR2, insulin receptor and downstream regulators (AKT , GSK3β, cyclin D1) was evaluated by qRT-PCR and Western blot, and the results were consistent with DGE. The effect of insulin on the HPNE-mut-Kras was suppressed with additional AKT inhibitor MK2206, the expression of downstream regulators was also suppressed. Upregulating SSTR2 restored insulin-reduced invasion and proliferation. Similarly, knock-down of mut-Kras suppressed insulin-induced AKT phosphorylation. Our study suggested that insulin might enhance the migration, invasion and proliferation of pancreatic ductal epithelial cells. This effect might be Kras-independent and mediated by SSTR2/AKT axis.