Nutritional modulation of tumor growth.

The relationship between tumor and host tissue proliferation as a function of protein calorie deficiency followed by balanced nutritional repletion was examined in a series of C3H female mice with MA16/C tumors. Tumor and host tissue DNA synthesis was determined in animals with subcutaneously implanted tumors who were randomized to either regular diet (RD) or a totally protein-free diet (PFD) for 5 days followed by refeeding for 4, 8, 12, 24, 36, 48, or 72 hr. Animals maintained on a protein-free diet demonstrated a decrease in DNA synthetic activity in both tumor and host tissues. Following refeeding of a regular diet to animals fed the protein-free diet, resumption of DNA synthesis in tumor preceded that of liver and was greatest by four hours of refeeding. In the liver, return of DNA synthetic activity was delayed but exceeded control levels by 36 hr. Compared to our previous studies examining the effects of starvation, we found that an isocaloric protein-free diet caused a smaller decrease in tumor DNA synthetic activity and an earlier resumption in tumor proliferation with the reinstitution of a normal protein diet. These studies suggest a nutrient-specific response for tumor and host tissues with nutritional deprivation and refeeding.