Effects of essential amino acid deficiencies on syngeneic tumor immunity and carcinogenesis in mice.

The present study was designed to evaluate in a syngeneic system the longterm effect of dietary reduction of each of three essential amino acids on carcinogenesis with methylcholanthrene (MCA) and immunity to a transplanted MCA tumor. Inbred mice were provided a standard amino acid diet or a diet deficient in isoleucine, leucine, or phenylalanine-tyrosine. In the carcinogenesis experiment, MCA pellets were implanted in each mouse and weekly records were maintained of body weight, tumor incidence, tumor size, and death rate. Mice in the immunity study were inoculated with syngeneic tumor cells; tumors were excised when the largest tumor in the control group reached 12 mm and each animal then received a second challenge of tumor cells. The available data suggest that (1) restriction of the selected amino acids does not inhibit chemical carcinogenesis with MCA, (2) phenylalanine-tyrosine deficiency may actually enhance chemical carcinogenesis with MCA, and (3) selected essential amino acid deficiencies do not enhance immunity to a transplanted MCA tumor.