IGF is a factor which takes a very important role in controlling proliferation, differentiation and cell death of epithelial cells of the breast, prostate, lung, colon and the like organs, and its action is carried out via an IGF receptor existing on the cell surface. Two types of IGF-I and IGF-II exist, and each of them comprises a single chain polypeptide and has about 40% homology with an insulin precursor proinsulin at the amino acid level.