Fig. 4.
UV light-induced skin cancer in mice. Mice were shaved once per week and irradiated three times per week with 3.75 kJ/m2 for 20 weeks or until the first skin tumor arose. Mice were inspected weekly for the development of skin tumors. Results with 12 Polη−/−/ι−/− mice (open circles) are compared with results reported (22) for 14 wild-type mice (open squares) and 12 homozygous Polη knockout mice (open diamonds), eight of which were Polι+/−, and four of which were Polι+/−. We also irradiated 13 Polη+/−/ι−/− mice and nine Polη+/+/ι−/− mice, none of which developed skin tumors after 20 weeks of irradiation (not plotted). In fact, the latter mice did not develop skin tumors after >41 weeks.