MGMT and neoplasm: According to previous reports, ATM can be activated during the DSBR [22], NER [48] and MGMT repair [49] processes against lethal alkylating damage, but the ATM inhibitor does not improve temozolomide sensitivity when the tumor highly expresses MGMT [50], this implies that temozolomide produces relatively low amount of ICL than MGMT repairable O-alkyl adducts on DNA.