Epidermal growth factor attenuates cell proliferation by down-regulating the transforming growth factor-β receptor in the osteoblastic cell line MC3T3-E1

Abstract

We investigated the role of transforming growth factor β 1 (TGF-β 1) in growth regulation of the murine osteoblastic cell line, MC3T3-E1. We detected TGF-β activity in the conditioned medium of MC3T3-E1 cells and its activity was increased by acid treatment of the bioassay system using CCl 64 cells. Northern blot analysis revealed the expression of TGF-β 1 precursor messenger ribonucleic acid (mRNA). MC3T3-E1 cells possessed a single class of high affinity TGF-β 1 receptor (2.8 × 10 4 sites per cell, K d = 196 pM). Cross-linking studies revealed three specific TGF-β receptors with molecular masses of 65, 95 and 280 kDa. Both TGF-β and epidermal growth factor (EGF) stimulated [ 3H]-thymidine incorporation into cells. EGF decreased the number of TGF-β receptor dose-dependently, and pretreatment of cells with 10 nM EGF attenuated cell growth by TGF-β. All these data suggested that TGF-β might be an autocrine growth factor in murine osteoblastic MC3T3-E1 cells and that EGF might modulate the growth of cells by down-regulating the TGF-β receptor level.