Expression patterns of insulin-like growth factor 1 (IGF-I) and its receptor in mammary tissues and their associations with breast cancer survival

The level of circulating insulin-like growth factor 1 (IGF-I) has been shown to be positively associated with breast cancer risk. The expression patterns of the IGF-I and its receptor IGFIR genes in breast tissues and their association with breast cancer survival remain unclear. In the present study, we quantified the mRNA levels of the IGF-I and IGFIR genes in both benign and malignant breast tumor tissues and their adjacent normal tissues. We then evaluated whether the expression patterns of these genes in breast cancer tissues are related to breast cancer survival. Included in the study were samples from 508 patients diagnosed with primary breast cancer, and 206 patients diagnosed with benign breast disease (BBD). Patients with BBD had a significantly higher IGF-I gene expression than patients with breast cancer in both tumor and adjacent non-neoplastic tissues. Among BBD patients, mRNA levels of the IGF-I gene were similar between tumor and tumor adjacent tissues. In cancer patients, however, the expression levels of these genes were substantially higher in tumor adjacent tissues than in tumor tissues. Patients with a high expression of the IGF-I gene in cancer tissues tended to have more favorable overall and disease-free survival. Our findings suggest that the expression of IGF-I and IGFIR genes may undergo substantial change over the course of breast tumorigenesis, and the pattern of changes may be associated with breast cancer prognosis.