To investigate whether the activity of Rac1 is required for HPV-8 induced papilloma formation, we compared the spontaneous occurrence of skin papillomas in K14 HPV-8 transgenic mice and mice expressing a myc tagged inhibitory mutant of Rac1, K14 N17Rac1, in addition to HPV-8, both in the basal compartment of the epidermis (K14 HPV-8/K14 N17Rac1) (Table 1, Figure 1B) [17]. This evidence concerns the gene KRT14 and skin papilloma.