Figure 1.

Establishment and characterization of irreversible gemcitabine (GEM) resistance in pancreatic cancer (PC) cell lines. A, Schematic diagram showing the establishment of GEM‐resistant cell lines. Briefly, parental cells were cultured in medium with increasing concentrations of GEM until resistance was acquired to the final concentration. B and C, 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay of parental (BxPC‐3 and CFPAC‐1) and GEM‐resistant (BxPC‐3‐GR and CFPAC‐1‐GR) cells exposed to GEM at different concentrations for 48 h. D and E, GEM sensitivity of BxPC‐3‐GR and CFPAC‐1‐GR cells cultured with GEM‐containing or ‐free medium for 30 d was determined by MTT assays. F and G, Apoptosis rates were significantly lower in GEM‐resistant cells than in their respective parental cell lines at the same GEM dose. H and I, Protein expression of poly adenosine diphosphate ADP‐ribose polymerase 1 (PARP1) and cleaved PARP1 (C‐PARP1) were compared between parental and GEM‐resistant cells using western blot analysis after incubating with different concentrations of GEM for 48 h. Glyceraldehyde 3‐phosphate dehydrogenase (GAPDH) was used as a loading control. ***P < .001; comparisons indicated by lines