185 Background: In human pancreatic cancer, expression of cMET is associated with poor survival. So far, activation/expression of cMET by hepatocyte growth factor (HGF) has been shown to induce proliferation and motility in cancer cells. Therefore, we hypothesized that inhibition of cMET in human pancreatic cancer cell lines impairs oncogenic signaling and tumor growth. Methods: Pancreatic cancer cell lines (HPAF-II, MiaPaCa2, L3.6pl, BxPC3, Panc02) and the cMET inhibitor INC280 (Novartis Oncology, Basel) were used. MiaPaCa2 and L3.6pl pancreatic cancer cells were grown with gemcitabine up to 500 and 250 nM, respectively (then called MiaPaCa2(G500) and L3.6pl(G250)). MTT and Boyden Chamber assays were used to determine effects of INC280 on growth and motility of cells in vitro. Expression of growth factor receptors, activation of signaling intermediates and expression of transcription factors were assessed by Western blotting. Finally, in vitro results were validated in an orthotopic tumor model using L3.6pl pancreatic cancer cell line. Results: All pancreatic cancer cell lines showed expression of cMET. In vitro treatment of cancer cells with INC280 led to a minor, dose-dependent inhibition of growth even when cells were supplemented with HGF. In contrast, migration assays showed a significant reduction of cancer cell motility upon INC280 when cells were stimulated with HGF (P<0.05). Regarding oncogenic signaling, INC280 led to inhibition of HGF-induced phosphorylation of AKT, ERK and FAK. In addition, c-Myc expression was diminished in cancer cells. Interestingly, gemcitabine resistant cell line MiaPaCa2(G500) showed higher cMET expression levels compared to the normal MiaPaCa2. Stimulation of MiaPaCa2(G500) with HGF led to strong induction of oncogenic signaling and tumor cell motility, an effect that was significantly diminished by INC280. Moreover, results from in vivo experiments show that therapy with INC280 (10 mg/kg/d) significantly reduces tumor growth as determined by final tumor weight (P<0.05). Conclusions: In pancreatic cancer cell lines, targeting cMET with INC280 abrogates oncogenic signaling in vitro and impairs tumor growth in vivo. Therefore, the concept of cMET inhibition warrants further preclinical evaluation.
Metformin inhibits pancreatic cancer cell and tumor growth and downregulates Sp transcription factors
