ATM and breast cancer: In agreement with the result of T24-ATM−/− BC cells showing high sensitivity to DSBs, regardless of BUB1B/BUBR1 expression level, ATM inhibition by AZD0156, substantially abrogated the resistance to IR treatment in T24-ATM+/+ with BUB1B/BUBR1 stable-overexpression cells (Fig. 5a).