The influence of dietary protein concentration and energy intake on mitogen response and tumor growth in melanoma-bearing mice.

The effects of energy deprivation and low or high dietary protein levels upon lymphocyte transformation of spleen cells from syngeneic tumor-bearing and control mice were studied in a murine model of malignant melanoma. Both T- and B-lymphocyte transformation were significantly stimulated by the presence of a growing melanoma. T-cell responses however, were dependent only upon dietary protein concentrations, not the level of energy intake; whereas, the converse was true for B cells. Moreover, mice fed stock diet had the lowest response to mitogens of all diets tested. Except for mice receiving a 15% casein diet, tumor weights were generally not affected by level of intake or the amount of dietary protein. Others have demonstrated that melanoma cells have a greater need for tyrosine or phenylalanine than other tumor cells; thus we hypothesized that lymphocyte transformation may be depressed by relatively low phenylalanine or tyrosine levels in the diet when protein intakes are limited by either a low dietary concentration a restricted intake of a diet containing adequate protein, or both.