Survival curves of mice given MNU treatment. (A) Duration of survival. Thirty-seven of MGMT−/− MLH1+/+, 37 of MGMT+/+ MLH1−/−, 38 of MGMT−/− MLH1−/−, and 36 of MGMT+/+ MLH1+/+ mice (each 6 weeks old) were given MNU (30 mg/kg of body weight) i.p. in the sixth postnatal week. These mice were observed for 30 days after the treatment. (B) Survival of mice given various doses of MNU. Six-week-old mice were given various doses of MNU i.p. For each dose 7 to 12 mice were used and data on survivors at 30 days after the administration were plotted. (○) MGMT−/− MLH1+/+; (▵), MGMT−/− MLH1−/−; (•), MGMT+/+ MLH1+/+ and MGMT+/+ MLH1−/− mice.