ATM and B-cell chronic lymphocytic leukemia: Bendamustine, a bifunctional alkylating agent, has received widespread use in CLL.28, 39, 40 Bendamustine induces double-strand DNA damage, purportedly its main mechanism of toxicity, as well as unique DNA repair responses such as base excision repair.25, 41 In lymphoma cell lines, bendamustine activated p53 via elevated expression and phosphorylation at S15,25 a target site of ATM, ATR and DNA-PK.