ATM-deficient human fibroblast cells are resistant to low levels of DNA double-strand break induced apoptosis and subsequently undergo drug-induced premature senescence

► A-T cells were not hypersensitive to low levels of DNA DSBs. ► A-T cells have enhanced Akt but defect in activation of p53 and apoptotic proteins. ► A-T cells underwent premature senescence after DNA damage accumulated. ► Chemotherapeutic effect in cancer therapy may be associated with premature senescence.