Influence of glucose concentration on growth and formation of necrosis in spheroids derived from a human bladder cancer cell line

Spheroids derived from the human bladder cancer cell line MGH-U1 were initiated in spinner culture and then transferred to multiwell plates which contained medium with varying concentrations of glucose and pyruvate. Growth of individual spheroids was monitored, and at different times after transfer spheroids were sectioned and the diameter of the necrotic center and the thickness of the viable rim were determined. In normal medium containing glucose (1 g/liter; 5.5 mM), spheroid diameter increased linearly with time, growing from approximately 400 micron to approximately 1200 micron in 8 days, and most spheroids did not develop central necrosis. Increase in glucose concentration up to 5 g/liter had no effect on spheroid growth. Lower glucose concentration decreased the rate of spheroid growth, but large effects were observed only at glucose concentration lower than 100 mg/liter. Spheroids developed central necrosis at 2-4 days after transfer to glucose-deficient medium, and the diameter of the necrotic center increased more rapidly than the diameter of the spheroid. There was an approximately linear relationship between thickness of the viable rim in 5-6-day spheroids and glucose concentration in the range of zero (rim thickness, approximately 150 micron) to 500 mg/liter (rim thickness, approximately 400 micron). The presence or absence of pyruvate (110 mg/liter) in the medium had no effect on spheroid growth or formation of necrosis. These results suggest that limited penetration of glucose may be one of the factors that contribute to cell death in solid tumors.