The tumor suppressor activity of DMTF1 may be partially explained by the role of DMTF1 in the transcriptional activation of Arf, leading to p53-dependent cell cycle arrest (16) and/or the binding of DMTF1 to p53, which promotes p53 stability and nuclear function (by antagonizing MDM2-mediated ubiquitination of p53) (17). The gene discussed is DMTF1; the disease is neoplasm.