G1 cell cycle arrest at 36 h post treatment with cisplatin, sodium arsenite and hyperthermia was confirmed by increased accumulation of P21 (CDKN1A), decreased retinoblastoma 1 (RB1) phosphorylation and stabilization of cyclin E. These data indicate that arsenite and hyperthermia disrupted the mitotic checkpoint in TP53-expressing ovarian cancer cells; undivided cells exited mitosis and accumulated in pseudo-G1 with 2C DNA content and subsequently underwent apoptosis. The gene discussed is CDKN1A; the disease is ovarian cancer.