The current lines of evidence supporting its role can be conveyed in (a) epidemiologic studies associating relatively high levels of circulating IGF-I to increased incidence of prostate, breast, and other cancers [35,36,37,38], and (b) other studies in vitro with human tumor cells implicating IGF-I in growth, survival, migration, and metastatic behavior upon activation of the expressed IGF-IR [39,40,41], as well as resistance to chemotherapeutic and radiation therapies [42]. The gene discussed is IGF1; the disease is cancer.