An increase in the number of cells growing in cell culture is the result of two opposing effects: an increase in the number of cells that traverse the cell cycle and divide into two daughter cells (mitosis), or a decrease in the number of cells that die according to different modalities, the most prominent one being apoptosis (1), or both. Insulin and IGF-I are both capable of facilitating cell progression through the cell cycle, and of inhibiting apoptotic mechanisms. In…