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 μM 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