However, because the mitogenic effects of IGF-1 are involved in the growth regulation of breast (Wolf et al., 1997) and prostate cancer (Chan et al., 1998; Wang and Wong, 1998) and because patients with IGF-1 hypersecretion (acromegaly) have a higher incidence of large bowel polyposis, the use of recombinant IGF-1 should be avoided in such patients or in those with a family history of these tumors. The gene discussed is IGF1; the disease is prostate cancer.