Simultaneous estimation of epidermal growth factor receptors and steroid receptors in a series of 136 resectable primary breast tumors

Human breast cancer cell lines, as well as human breast cancer biopsies, possess specific high-affinity epidermal growth factor receptors (EGF-r). However, reports on the presence of EGF-r in human breast cancer biopsies are still controversial, especially concern-ing the relationship between EGF-r and other biological variables whose prognostic relevance is well known, such as the estrogen (ER) and progesterone (PgR) receptors. In the present study, the EGF-r content was estimated in a series of 136 unselected breast cancer primaries along with cytoplasmic (ERc) and nuclear (ERn) ER and cytoplasmic PgR. EGF-binding activity consisted of a single class of high-affinity binding sites (K_d = 0.55 nM) and ranged from 0 to 275 fmol/mg protein. We observed a strong inverse association between EGF-r and ERc (p <0.001); in fact, about two thirds of the tumors were ERc-positive/EGfir-negative or ERc-negative/EGF-r-positive. The same type of association was found between EGF-r and either ERn or PgR. Kendall’s rank correlation test confirmed that the EGF-r concentrations were correlated with the levels of ERc (τ = -0.291, p <0.0001), ERn (τ = -0.27, p <0.0005) and PgR (τ = -0.162, p <0.01). The EGF-r content was significantly higher (p <0.0001) in the ERc-negative tumors (72.6 ± 54.4 fmol/mg protein) as compared to the ERc-positive ones (33.0 ± 37.4 fmol/mg protein). Similarly, the subset of PgR-positive tumors was characterized by lower EGF-r mean concentrations when compared to PgR-negative cases (35.4 ± 54.4 vs. 63.8 ± 54.4 fmol/mg protein). These results confirm the previously described inverse rela-tionship between EGF-r and steroid receptors. Moreover, they suggest the existence of an interaction between steroid hormones and EGF and support the need for further studies to better understand their respective roles in modulating breast cancer growth.