Enhancement of the antiproliferative activity of gemcitabine by modulation of c-Met pathway in pancreatic cancer.
Pancreatic-ductal-adenocarcinoma (PDAC) is amongst the most lethal malignancies, mainly because of its metastatic spread and multifactorial chemoresistance. Since c-Met is a marker of pancreatic-cancer-stem-cells (CSC), playing a key role in metastasis and chemoresistance, this study evaluated the therapeutic potential of the novel c-Met/ALK inhibitor crizotinib against PDAC cells, including the Capan-1-gemcitabine-resistant cells (Capan-1-R). Crizotinib inhibited PDAC cell-growth with IC50 of 1.5 ?M in Capan-1-R, and synergistically enhanced the antiproliferative and proapoptotic activity of gemcitabine, as detected by sulforhodamine-B-assay, flow cytometry and combination-index method. Capan-1-R had higher expression of the CSC markers CD44+/CD133+/CD326+, but their combined expression was significantly reduced by crizotinib, as detected by quantitative-RT-PCR and FACS-analysis. Similarly, Capan-1-R cells had significantly higher protein-expression of c-Met (?2-fold), and increased migratory activity, which was reduced by crizotinib (e.g., > 50% reduction of cell-migration in Capan-1-R after 8-hour exposure, compared to untreated-cells), in association with reduced vimentin expression. Capan-1-R had also significantly higher mRNA expression of the gemcitabine catabolism-enzyme CDA, potentially explaining the higher CDA activity and statistically significant lower levels of gemcitabine-nucleotides in Capan-1-R compared to Capan-1, as detected by Liquid-chromatography-massspectrometry. Conversely, crizotinib significantly reduced CDA expression in both Capan-1 and Capan-1-R cells. In aggregate, these data show the ability of crizotinib to specifically target CSC-like-subpopulations, interfere with cell-proliferation, induce apoptosis, reduce migration and synergistically interact with gemcitabine, supporting further studies on this novel therapeutic approach for PDAC.