Checkpoint kinase inhibitor AZD7762 strongly sensitises urothelial carcinoma cells to gemcitabine

Background: more effective chemotherapies are urgently needed for bladder cancer,a major cause of morbidity and mortality worldwide. we therefore explored the efficacy of the combination of gemcitabine and azd7762,a checkpoint kinase 1/2 (chk1/2) inhibitor,for bladder cancer. methods: viability,clonogenicity,cell cycle distribution and apoptosis were assessed in urothelial cancer cell lines and various non-malignant urothelial cells treated with gemcitabine and azd7762. dna damage was assessed by γh2a.x and 53-bp1 staining and checkpoint activation was followed by western blotting. pharmacological inhibition of chk1 and chk2 was compared to downregulation of either chk1 or chk2 using sirnas. results: combined use of gemcitabine and azd7762 synergistically reduced urothelial carcinoma cell viability and colony formation relative to either single treatment. non-malignant urothelial cells were substantially less sensitive to this drug combination. gemcitabine plus azd7762 inhibited cell cycle progression causing cell accumulation in s-phase. moreover,the combination induced pronounced levels of apoptosis as indicated by an increase in the fraction of sub-g1 cells,in the levels of cleaved parp,and in caspase 3/7 activity. mechanistic investigations showed that azd7762 treatment inhibited the repair of gemcitabine-induced double strand breaks by interference with chk1,since sirna-mediated depletion of chk1 but not of chk2 mimicked the effects of azd7762. conclusions: azd7762 enhanced sensitivity of urothelial carcinoma cells to gemcitabine by inhibiting dna repair and disturbing checkpoints. combining gemcitabine with chk1 inhibition holds promise for urothelial cancer therapy. © 2017 the author(s).