Inhibition of transplanted carcinomas in mice by retinoids but not by vitamin C.

A squamous cell carcinoma (ASB XIII) and a large cell carcinoma (ASB XIV) induced from mouse lung cells by chrysotile asbestos were established in serial transplant in BALB/c mice. New hosts were treated with retinoids by ip injection at 10 mg/kg 5 days/week. Growth inhibition of ASB XIII was 58%-64% (P less than 0.005) after treatments with all-trans retinoic acid, 52% after trimethylmethoxyphenyl analog, ethyl ester, 26% (not significant) after 13-cis retinoic acid. Growth inhibition of ASB XIV was 39% (P less than 0.02) after injections of all-trans retinoic acid, and 33% (P greater than 0.05) after trimethylmethoxyphenyl analog, ethyl ester. After daily oral administration of 10 mg/kg of all-trans retinoic acid in feed, there was 61%-81% inhibition (P less than 0.005) of ASB XIII. Growth of ASB XIII was not significantly inhibited by daily im injections of 200 mg/kg of vitamin C.