Interest in insulin-like growth factors (IGFs) and their effect on carcinogenesis
has increased recently because high serum concentrations of IGF1 are associated with
an increased risk of breast, prostate, colorectal, and lung cancers. Physiologically,
IGF1 is the major mediator of the effects of the growth hormone; it thus has a strong
influence on cell proliferation and differentiation and is a potent inhibitor of apoptosis.
The action of IGF1 is predominantly mediated through the IGF1 receptor (IGF1R). IGF1R
is involved in several oncogenic transformation processes. The availability of unbound
IGF1 for interaction with IGF1R is modulated by IGF-binding proteins (IGFBP1-6). IGFBPs,
especially IGFBP3, have independent effects on cell growth, for example, IGFBP3 has
proapoptotic activities both dependent on and independent of p53.