KRT14 and skin papilloma: All of these K14 HPV-8/K14 L61Rac1 double transgenic mice (8 out of 8) developed skin papillomas by P140 (Figure 2B, 2D), while only 18% of the K14 HPV-8 mice without expression of L61Rac1 developed papillomas and none of the K14 L61Rac1 mice developed papillomas.