ATM and breast cancer: To investigate the cytotoxic effect of combined EZH2 and ATM inhibition in human BRCA1-mutant breast cancer, we treated the human TNBC cell lines SUM149 (BRCA1-mutant) and CAL120 (BRCA1-wild type) with GSK126 and AZD1390, and analyzed cell viability using CellTiter-Glo and clonogenic survival (Fig. 4A, B).