RAC1 and skin neoplasm: We observed that 9 out of 11 (81.8%) K14 HPV-8 mice developed visible skin tumors, starting from a cumulative UV-light dose of approximately 5 J/cm2, whereas only 3 out of 9 (33.3%) K14 HPV-8/Rac1-EKO mice developed clinically apparent tumors starting from a cumulative UV-light dose of approximately 15 J/cm2 (Figure 4A–4C).