Autocrine growth mechanism by transforming growth factor (TGF)‐β1 and TGF‐β1‐receptor regulation by epidermal growth factor in a human endometrial cancer cell line IK‐90

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Abstract
Transforming growth factor-β1 (TGF-β1) enhanced cell proliferation in a concentration-dependent manner in a human endometrial cancer cell line, IK-90. Scatchard analysis of TGF-β1 receptor in IK-90 cells, using 125I-TGF-β1 as a ligand, revealed the presence of a class of high-affinity TGF-β1 receptors (2,000 sites per cell, KD = 74pM). Moreover, IK-90 cells produced and secreted TGF-β1: TGF-β1 messenger RNA was detected at 2.5 and 4.0 kb by Northern-blot analysis using 32P-labeled TGF-β1 cDNA as a probe, and TGF-β1 activity in conditioned medium by the inhibition of 3H-thymidine uptake into CCI 64 mink lung epithelial cells. We investigated the regulation of TGF-β1 receptor by 4 kinds of growth factor: epidermal growth factor (EGF) but not TGF-β1 insulin or insulin-like growth factor-I increased the level of TGF-β1 binding sites in a concentration- and time-dependent manner. These findings suggest that TGF-β1 may be a potential autocrine growth factor in a human endometrial cancer cell line IK-90 and that this autocrine mechanism may be affected by EGF.