The insulin-like growth factor (IGF) system performs multiple functions in the regulation of breast cancer cell growth. The IGF system is comprised of a complex network of ligands, receptors and related signaling proteins. Two receptors are recognized, the insulin-like growth factor-I receptor (IGF-IR) and the insulin-like growth factor-II receptor (IGF-IIR), one of which, the IGF-IR, is a transmembrane heterodimer structurally similar to the insulin receptor. The activation of the IGF-IR results in the recruitment of adapter proteins, which adapter proteins used by the insulin-like growth factor-I (IGF-I) to transduce its signal to the insulin receptor substrate-1 (IRS-1). This study investigated the relationship between IGF-IR and IRS-1 by using an immunohistochemical staining technique.

IGF-IR and IRS-1 expression was detected by immunohistochemical staining using paraffin sections in 123 invasive breast carcinoma cases. The results were evaluated with the survival rate and the clinicopathological prognostic variables such as the patient's age, the clinical stage, the histological grade, the estrogen receptor (ER) and the progesterone receptor (PR).

The results showed that IGF-IR and IRS-1 expression positively correlated with the ER and PR, and an inverse relationship was found between the IGF-IR and IRS-1 and histological grades. No association was observed between the IGR-IR and IRS-1 and the patent's age and clinical stage. In survival analysis, there was no definite association between the expressions of IGF-IR and IRS-1 and the disease free survival rate.

IGF-IR and IRS-1 appear to play a role in the progression and differentiation of breast cancer in association with the ER and the PR.