Constitutive and regulated secretion of epidermal growth factor and transforming growth factor-β1 in MDA-MB-231 breast cancer cell line in 11-day cultures

Epidermal growth factor (EGF) and transforming growth factor type beta(1) (TGF-beta(1)) 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 Ii-day cultures of these cells were collected to measure EGF and TGF-beta(1) 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-beta(1). These cells secreted constitutively quantifiable concentrations of both factors to the CM. EGF treatment inhibited TGF-beta(1) levels in CM throughout the study period (P = 0.002), while EGF levels diminished after TGF-beta(1) treatment (P = 0.05). This finding suggests a dual regulation between EGF and TGF-beta(1), at a protein level, in this cell line. CELL SIGNAL 11;10:753-757, 1999. (C) 1999 Elsevier Science Inc.