SECRETION AND BINDING OF INSULIN-LIKE GROWTH FACTOR-I BY A HUMAN MEDULLARY-THYROID CARCINOMA CELL-LINE
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- Published online on: June 1, 1993 https://doi.org/10.3892/ijo.2.6.961
- Pages: 961-967
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Abstract
The TT human medullary thyroid carcinoma cell line secretes a 7.5 kD species with insulin-like growth factor (IGF-I) immunoreactivity and HPLC mobility and expresses IGF-I mRNA. Conditioned medium also contained IGF-binding activity with a pattern of displacement of [I-125]-IGF-I characteristic of IGF binding proteins. Western ligand analysis and immunobloting with anti-IGFBP4 antiserum identified a 34 kD IGF-I binding species. Northern analysis identified a 2.1 kb IGFBP4 mRNA species. Cell surface binding of [I-125]-IGF-I identified Type I IGF receptors. TT cells constitute a useful model to study the IGF-I autocrine system in the transformed state.