BRCA1 suppresses insulin-like growth factor-I receptor promoter activity: Potential interaction between BRCA1 and Sp1

Sharon B. Maor, Shirley Abramovitch, Mike R. Erdos, Lawrence C. Brody, Haim Werner

Research output: Contribution to journalArticlepeer-review

Abstract

The insulin-like growth factor I receptor (IGFI-R) has an important role in breast cancer etiology. The receptor is overexpressed by most breast cancers, where it functions as a potent antiapoptotic agent. BRCA1 is a tumor suppressor gene that is mutated in a large fraction of familial breast and ovarian cancers. Cotransfection of Saos-2, MCF7, and CHO cells with IGF-I-R promoter constructs driving luciferase reporter genes, and with a BRCA1 expression vector, suppressed promoter activity in a dose-dependent manner. Functional interactions between BRCA1 and Sp1 in the regulation of the IGF-I- R gene were studied in Schneider cells, a Drosophila cell line which lacks endogenous Sp1. In these cells BRCA1 suppressed 45% of the Sp1-induced trans- activation of the IGF-I-R promoter. These results suggest that BRCA1 is capable of suppressing the IGF-I-R promoter in a number of cell lines, thus resulting in low levels of receptor mRNA and protein. Mutant versions of BRCA1 lacking trans-activational activity can potentially derepress the IGF- I-R promoter. Activation of the overexpressed receptor by locally produced or circulating IGFs may be a crucial step in breast and ovarian cancer progression. (C) 2000 Academic Press.

Original languageEnglish
Pages (from-to)130-136
Number of pages7
JournalMolecular Genetics and Metabolism
Volume69
Issue number2
DOIs
StatePublished - Feb 2000

Keywords

  • BRCA1
  • IGF-I receptor
  • Sp1
  • Tumor suppressor

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