The effects of streptozocin-induced diabetes and weight-matched pair feeding on tumor growth and survival in Fischer rats.

Overview

Sixty-one 150- to 180-g Fischer rats were assigned to one of four experimental groups: nondiabetic, tumor bearer (ND-TB, n = 15); diabetic, non-tumor bearer (D-NTB, n = 19); diabetic, tumor bearer (D-TB, n = 16); or nondiabetic, weight-matched control, tumor bearer (WM-TB, n = 11). The WM group was housed in metabolic cages and fed H2O ad libitum and rat chow to achieve appropriate carcass weight (comparable to D-NTB). Diabetes was induced with a single dose of streptozocin (STZ) 40 mg/kg body wt iv, 10 days prior to tumor inoculation. Viable methylcholanthrene-induced sarcoma cells (1 X 10(6) ) were injected into the right flank on Day O. Body weight and tumor volume were assessed every 3 days. On the day of death, the animal and excised tumor were weighed. Dividing the growth curves versus time into two phases based on tumor volumes 0-20 and 20-60 cm3 defined a significant early growth (0-20 cm3) delay of 5 days in the D-TB and WM groups vs the ND-TB group. The growth rate from 20-60 was not different in any group. Tumor growth retardation seen in STZ-induced diabetic animals can be mimicked and exceeded in a pair-fed, weight-matched control group. Diabetic and starved animals have smaller tumors and live longer than ad lib fed, nondiabetic animals. The delay in tumor growth is a reflection of the retardation in the early (0-20 cm3) growth rate.