CHEK1 and endometrial cancer: For the reason above, we concluded that both the inhibitors enhanced the effect of irradiation in endometrial cancer cells: the ATR inhibitor, VE822, inhibited the activation of the ATR-Chk1 pathway induced by irradiation; and the ATM inhibitor, KU60019, inhibited the activation of the ATM-Chk2 pathway, also caused by irradiation.