In this study, we demonstrate the following: 1) KU60019, an ATM inhibitor interferes with the association of ATM with TOP2β and blocks TOP2β ubiquitination, thereby causing a dose and time-dependent accumulation of TOP2β; 2) Inactivation of ATM by KU60019 increases the level of the TOP2β-DNA cleavage complex and impairs the repair of VP-16 induced DSBs; 3) the therapeutic combination regimen synergistically suppressed the survival of lung cancer cells by promoting apoptosis. The gene discussed is TOP2B; the disease is lung cancer.