Chondrosarcoma growth: influence of diabetes, caloric restriction, and insulin treatment

Diabetes and malnutrition result in decreased somatomedin production and cartilage growth in rats. The growth and metabolism of the Swarm rat chondrosarcoma are dramatically affected by somatomedins. Data presented here show that streptozotocin diabetes and diet restriction inhibit in vivo chondrosarcoma growth. Tumors grown in diabetic rats were significantly smaller than tumors grown in diet-restricted rats showing the same changes in body weight. Insulin treatment increased the rate of tumor growth in diabetic rats. Tumors grown in rigidly controlled diabetic rats were as large as tumors grown in nondiabetic controls. Diet restriction and diabetes reduced the capacity of the serum of the rat to stimulate alpha-amino[14C]isobutyrate uptake and [3H]uridine incorporation into RNA in chondrosarcoma pieces grown in nondiabetic rats. This somatomedin activity of the serum was restored by treating diabetic rats with insulin. There was a significant correlation between the in vitro stimulatory effect of a particular serum pool on chondrosarcoma metabolism and in vivo chondrosarcoma growth in the animals from whom the serum was obtained. These studies demonstrate that the in vivo growth of malignant chondrocytes is similar to that of normal chondrocytes with respect to the role of nutrition and insulin.