The effect of protein depletion upon tumor growth and host survival

Abstract Malnutrition has been implicated as an important factor in the host's response to tumor. This study examined the role of protein depletion upon tumor growth and host survival in 20 male Fischer F344 rats (250 g). Ten rats were inoculated subcutaneously with 5 × 10 6 tumor cells (methylcholanthrene-induced bladder carcinoma). For 14 days all 20 rats were maintained on regular diet pellets (23% protein) (P). By Day 8, the 10 inoculated rats had palpable tumors. On Day 14, half the tumor (T) and control (C) rats were placed on a protein-free (PF) diet. CP rats gained weight gradually reaching a plateau at 325 g by Day 60. TP rats maintained their body weights between 250 and 270 g. TPF and CPF rats lost about 45 g/rat by Day 28; TPF rats lost significantly more weight during the ensuing 36 days. TP and CP rats consumed 15–20 g diet/day while TPF and CPF ate 10–15 g. Tumor growth was similar up to Day 28 after which TP rats had significantly increased tumor volumes. By Day 57, 4 5 TP rats were dead with metastatic disease while only 1 5 TPF rats had died. Mean survival for the TPF rats was 3.8 days longer than that of TP rats. These results demonstrate that tumor-bearing rats on a 23% protein diet have larger tumors and do not survive longer than rats on a protein-free diet. This observation may have significant implications for the nutritional management of cancer patients.