Thus, our finding of a distinct difference in tumor-free survival of Tax+p53−/− compared to Tax+p53+/+ mice indicates that Tax inactivation of p53 (i.e. Tax+p53+/+) is qualitatively less stringent than genetic inactivation of p53 (i.e. Tax+p53−/−). The gene discussed is CNTN2; the disease is neoplasm.