We further demonstrate that inhibition of ATM/ATR-mediated cell cycle arrest leads BJ-T p53sh and an isogenic RAS and SV40-transformed cell line (BJ-LSTR) to undergo mitotic catastrophe and subsequent CX-5461-mediated cell death in vitro and improves the therapeutic efficacy of CX-5461 in targeting aggressive Tp53-null (Tp53−/−) MYC-driven lymphomas in vivo. The gene discussed is TP53; the disease is lymphoma.