AZD8055 blocks radiation-induced mTOR phosphorylation and sensitizes pancreatic cancer cells to radiotherapy. (A) Chemical structure of mTOR dual inhibitor AZD8055, [5-[2,4-Bis((3S)- 3-methylmorpholin −4-yl)pyrido[2,3-d]pyrimidin-7-yl]-2-methoxyphenyl]methanol. (B) PANC-1 cells were treated with indicated doses of radiation in the absence or presence of AZD8055 for 48 h, Cell growth inhibition was analyzed by SRB assay. Error bars represent as mean ± SD. *, P < 0.05 vs. control or IR treatment alone and **, P < 0.01 vs. control or IR treatment alone. (C) PANC-1 cells were treated with radiation or AZD8055, alone or in combination, and cell viability was analyzed by colony formation assay. The experiment was repeated three times and the number of colonies was presented as mean ± SD. **, P < 0.01 vs. IR or AZD8055 treatment alone.