Figure 2. Absence of p53 in epidermis predispose to tumor development in a two-stage chemical carcinogenesis protocol.

A. Timeline of the skin carcinogenesis experiment. 8 to 9 week-old mice were shaved, and three days later treated topically with the carcinogen DMBA. TPA was administered twice a week for 12 weeks. Tumor sampling extended until week 18 in p53^EKO mice. B. Representative example of a p53^wt (left) or p53^EKO (right) mouse at week 14. Note the small pedunculated skin tumors with papillomatous aspect in the p53^wt mouse and the larger skin tumors in p53^EKO mice (arrowheads); in addition, some of the tumors in p53^EKO mice are sessile and ulcerated, resembling malignant carcinomas (arrows). C. Tumors emerge earlier in p53^EKO mice than in p53^wt mice when subjected to a DMBA/TPA chemical carcinogenesis protocol. D. Time evolution of mean tumor number by phenotypes. p53^EKO mice developed more tumors than p53^wt mice. Asterisks indicate p value < 0.05 in the t-Student test. E. Size distribution of skin tumors in p53^EKO and p53^wt mice. Note the earlier emergence and the higher number of medium (diameter > 2 mm) and large (diameter > 5 mm) tumors in p53^EKO mice in comparison to p53^wt mice.