Since p53 stabilization and activation is a multistep and tightly regulated process, in principle, the prerequisite for the antitumor efficacy of drugs inhibiting ribosome biogenesis should be the presence in the tumor cells, other than a normally functioning p53, also of those factors necessary for the activation of p53 and the induction of a p53-mediated cell cycle arrest and/or the apoptosis. The gene discussed is TP53; the disease is neoplasm.