TP53 and cancer: It is also known that the loss of function of the tumor suppressor gene p53 (p53−/−) is required for cancer progression in naevi. However, the long time lapse and rarity of melanoma tumor formation (one to three in a fish’ lifetime) in zebrafish carrying both BRAF V600E and p53−/− mutations, imply that there are other molecular alterations and pathways playing a role in melanoma formation.