Constitutive and regulated secretion of epidermal growth factor and transforming growth factor-beta1 in MDA-MB-231 breast cancer cell line in 11-day cultures.

Epidermal growth factor (EGF) and transforming growth factor type beta1 (TGF-beta1) exert opposite effects in most cells. A potential regulation between the two factors has been studied at a transcriptional level, but never at a protein level. MDA-MB-231 is a breast carcinoma cell line which possesses large quantities of membrane receptors and expresses high activities for both factors. In this study, conditioned mediums (CM) of 11-day cultures of these cells were collected to measure EGF and TGF-beta1 by immunochemical assays. Four types of cultures were tested: (1) controls; (2) after treatment with 17-beta-estradiol; (3) treated with EGF; and (4) treated with TGF-beta1. These cells secreted constitutively quantifiable concentrations of both factors to the CM. EGF treatment inhibited TGF-beta1 levels in CM throughout the study period (P = 0.002), while EGF levels diminished after TGF-beta1 treatment (P = 0.05). This finding suggests a dual regulation between EGF and TGF-beta1, at a protein level, in this cell line.