Intratumoral IGF-I protein expression is selectively upregulated in breast cancer patients with BRCA1/2 mutations.

BRCA1/2 mutations predispose to early onset breast and ovarian cancers. The phenotypic expression of mutant alleles, however, is thought to be modified by factors that are also involved in the pathogenesis of sporadic breast cancer. One such protein is IGF-I, one of the strongest mitogens to breast cancer cells in vitro.