Constitutive and regulated secretion of epidermal growth factor and transforming growth factor-beta(1) 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 b etween the two factors has been studied at a transcriptional level, but nev er at a protein level. MDA-MB-231 is a breast carcinoma cell line which pos sesses large quantities of membrane receptors and expresses high activities for both factors. In this study, conditioned mediums (CM) of Ii-day cultur es of these cells were collected to measure EGF and TGF-beta(1) by immunoch emical assays. Four types of cultures were tested: (1) controls; (2) after treatment with 17-beta-estradiol; (3) treated with EGF; and (4) treated wit h TGF-beta(1). These cells secreted constitutively quantifiable concentrati ons of both factors to the CM. EGF treatment inhibited TGF-beta(1) levels i n CM throughout the study period (P = 0.002), while EGF levels diminished a fter TGF-beta(1) treatment (P = 0.05). This finding suggests a dual regulat ion between EGF and TGF-beta(1), at a protein level, in this cell line. CEL L SIGNAL 11;10:753-757, 1999. (C) 1999 Elsevier Science Inc.