Cancer cells often overexpress both IGF-IR and IR
Since the activation of the Ras pathway mediates cellular mitogenic responses, the effect of insulin in increasing the pool of farnesylated p21Ras amplifies the mitogenic effects of insulin itself and other growth factors, such as IGF-I. This mechanism could explain the exaggerated mitogenic response to growth factors in patients with high levels of circulating insulin
As mentioned before, the long-term exposure to hyperinsulinemia consequent to insulin resistance provides a link between diabetes, obesity, and cancer.