Immunological prophylaxis of chemical carcinogenesis in mice. I. Effect of immunization with insoluble lipoprotein of tumor cells on methylcholanthrene carcinogenesis.

Attempts were made to prevent methylcholanthrene tumorigenesis in mice by immunization with the insoluble lipoprotein of methylcholanthrene-induced sarcomas of the same strain of mice. Swiss/Mk mice were intensively immunized with the insoluble lipoprotein fraction extracted by the Thomas method or with the supernatant fraction of isogenic methylcholanthrene-induced tumor cells, or normal cells with Freund adjuvant. As control groups, mice pretreated with Freund adjuvant alone and untreated mice were prepared. Each mouse was injected with 0.5mg of 3methylcholanthrene*4 as a pellet or an olive oil suspension. Several series of repeated experiments always revealed the inhibitory effect of immunization with the insoluble lipoprotein fraction of a tumor on tumor occurrence. The tumor supernatant showed a slight inhibitory effect but was not so marked as the insoluble lipoprotein fraction. Tumor occurrence in groups immunized with normal insoluble lipoprotein or normal supernatant and that of adjuvant injection showed no significant difference from that in untreated group. Neither histological nor biological differences have been found among the developing tumors in the experimental groups.