↓ Clonogenic ability of carcinoma. ↑ Apoptosis associated with the activation of caspase-3 and PARP cleavage in 4T1 cells. ↑ Depletion of Bcl-xL protein in 4T1 cells. Longer survival time, reduced tumor size, and higher numbers of apoptotic 4T1 cells. Normal NMuMG cells are less sensitive to ATR. Here, BCL2L1 is linked to carcinoma.