Carcinogenicity in mice of some fatty acid methyl esters. 1. Skin application.

Abstract

Two oxygen‐containing derivatives of unsaturated fatty acids, methyl 12‐oxo‐trans‐10 octadecenoate and methyl hydroxyoctadecadienoate, both highly active in the newt test for carcinogenicity, have been tested as complete carcinogens and as promoting agents by application to the skin of ST/a mice. Through observation for two years the tumourigenic effect was recorded and compared with that of methyl oleate and of adequate positive control substances: 7,12‐dimethylbenz[α]anthracene and croton oil. Both methyl oxooctadecenoate and hydroxyoctadecadienoate showed a significant potency to promote the induction of skin papillomas. The genesis of malignant skin tumours was promoted by methyl oleate and oxooctadecenoate, and all the three methyl esters had a weak activity as complete carcinogens to the skin. As a systemic effect all the esters promoted the induction of malignant lymphomas, most markedly methyl oxooctadecenoate. Even without preceding initiation this ester and methyl oleate had some activity in lymphoma cancerogenesis. The various observations show that, when tested by our experimental procedures, methyl oxooctadecenoate is the ester most active in the induction of tumours, and the effect is essentially that of a promoter. The relation between molecular configuration and carcinogenicity of fatty acids is discussed.