Receptors for epidermal growth factor and insulin-like growth factor I and their relation to steroid receptors in human breast cancer

Levels of epidermal growth factor receptor (EGF-R) and insulin-like growth factor receptor (IGF-R) in breast cancer tissue were evaluated. The binding of growth factors was compared to the content of estrogen receptors (ER) and progesterone receptors (PgR). EGF-R correlated negatively to the ER and PgR (Kendall correlation, P less than 0.001), whereas the IGF-R correlated positively to ER and PgR (analysis of variance, P less than 0.001). In contrast, no correlation was found between EGF-R and IGF-R. IGF-R binding was higher in tumor tissues than in adjacent normal tissues (Wilcoxon rank test, P less than 0.001), whereas the EGF-R binding in normal tissue did not differ from that in cancer tissue. The degree of differentiation in ductal breast cancer correlated to EGF-R (chi 2 test, P = 0.018), but not to IGF-R. The bindings of both growth factors were the same in metastases and primary breast tumors. Our results show that EGF-R and IGF-R are present in normal breast tissue and breast cancer tissue. The growth factor receptors are related to steroid receptor content and their presence is associated with malignant transformation of breast cells and dedifferentiation of breast cancer.