TP53 and neoplasm: If u2 = 1 day-1 (all cancer cells are in apoptosis), TD → ∞ and α = 0 (tumor self-destruction), in contrast to the failure of the apoptosis mechanism in malignant tumors (because of the gene p-53 is repressed) and the existence of other cell loss mechanisms (metastasis, necrosis and exfoliation) [10, 11, 22].