Figure 4.

Chronic but not acute IGF-I depletion decreases the growth of hepatic metastases in obese and lean mice. Mice were maintained on regular chow or high-calorie diet for 8 to 10 wk. A single injection of tamoxifen (Tam, 0.4 mg) was administered to mice 4 d before or after the intrasplenic/portal inoculation of 5 × 10⁴ MC-38 cells, mice were splenectomized 1 min later, and livers were harvested 2 wk following tumor cell injection. A, incidence of hepatic metastases is expressed as percent mice with visible metastases. B, metastatic burden was calculated as fold increase in liver weight as compared to livers of tumor-free lean mice. Left, the mean weights (±SEM) of livers obtained from control lean mice noninjected with tumor cells were set as 1 (n = 8). The mean weights (±SEM) of livers obtained from control obese mice noninjected with tumor cells (n = 14), also shown on the left, did not differ significantly from lean controls (P = 0.2), indicating that the baseline mean liver weight in the two groups was comparable. Right, fold increase in liver weight of mice harboring hepatic metastases, injected with tamoxifen before or after tumor cell inoculation.