Effect of Essential Amino Acid Restriction on the Growth of Female C57BL Mice and Their Implanted BW10232 Adenocarcinomas

When diets devoid of a single essential amino acid are fed to rats or mice bearing malignant tumors, tumor growth is inhibited, but host weight is also markedly depressed. Recently, diets containing low but nutritionally adequate levels of phenylalanine and tyrosine were reported to inhibit tumor growth without adversely affecting the host. In the present study, diets containing decreasing levels of each essential amino acid were used to study the growth requirements of normal mice and the effect of single essential amino acid restriction on tumor-bearing mice and on the growth of their tumors. Amino acids required by these mice expressed as percentage of diet, in general were quantitatively similar to the maintenance requirements of the rat. Dietary levels of tryptophan, threonine, leucine, or methionine which significantly inhibited tumor growth, significantly depressed host weight as well. Reducing dietary levels of phenylalanine, valine, or isoleucine significantly inhibited tumor weight without affecting host weight. Lysine restriction had no effect on weight gain or tumor growth. Findings with valine, isoleucine, and leucine suggest that amino acid interrelations previously described in intact animals exist in tumor-bearing animals and may offer an approach to tumor inhibition.