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Mol Cell Endocrinol. 1991 Jun;78(1-2):71-8.

Identification and regulation of insulin-like growth factor binding proteins produced by hormone-dependent and -independent human breast cancer cell lines.

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Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey 17033.


Using molecular hybridization, ligand blotting and immunoprecipitation, our studies were designed to identify the insulin-like growth factor binding proteins (IGFBPs) produced by human breast cancer cells in culture and evaluate their regulation by estradiol (E2) and polyamines (PA). We demonstrate that the hormone-dependent MCF-7 and -independent BT-20 cell lines express the mRNA for IGFBP-2 (1.7 kb) and secrete this BP (31 kDa) in the conditioned medium. In contrast, the hormone-independent MDA-MB-231 cell line does not express the IGFBP-2 gene, while synthesizing and secreting IGFBP-1. E2 administration (10(-9) M) did not significantly influence IGFBPs secretion in MCF-7 cells. Addition of alpha-difluoromethylornithine (DFMO, 4 mM), an inhibitor of PA biosynthesis, consistently lowered IGFBP-2 mRNA in the MCF-7 and BT-20 cell lines and IGFBP-1 mRNA in MDA-MB-231 cells. Surprisingly, however, this compound either did not influence IGFBPs secretion in MCF-7 cells or actually increased their secretion in the BT-20 and MDA-MB-231 cell lines. PA involvement in IGFBPs production by breast cancer cells is complex and may involve differential regulation of transcriptional and post-translational events.

[Indexed for MEDLINE]

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