Table 1.

Epithelial tumors in K5.Myc transgenic mice

Genotype	Number of Mice (Gender)	Tumor incidence at 1 year, %	Average age of onset, weeks	Tumor types
E2f2 +/+	16 (6 F, 10 M)	37.5	42.6	One basal cell tumor of the skin and five SCC of oral cavity, of which three were invasive
E2f2 +/−	26 (14 F, 12 M)	73.1	43.6	One papilloma, five SCC of skin and fourteen SCC of oral cavity, of which six were invasive*
E2f2 −/−	25 (11 F, 14 M)	88.0	40.3	One papilloma, six SCC of skin and seventeen SCC of oral cavity, of which three were invasive*

^*All K5.Myc mice wild type for E2f2 showed only one tumor per mouse, whereas some E2f2 heterozygous and null mice developed more than one tumor per mouse, typically a SCC of skin and SCC of oral cavity. F, female; M, male; SCC, squamous cell carcinoma