Results here showed that there was no difference in survival for mice bearing Trp53−/−;Brca1−/− tumours compared to Trp53−/− (median time to reach humane endpoint 46 and 47 days respectively, p = NS), but deletion of either Pten or Nf1 expression significantly accelerated growth compared to p53 loss alone (Trp53−/−;Pten−/− 34 days, p < 0.0001; Trp53−/−;Nf1−/− 36.5 days, p < 0.0001). The gene discussed is PTEN; the disease is neoplasm.