Complex regulation of the fibroblast growth factor-binding protein in MDA- MB-468 breast cancer cells by CCAAT/enhancer-binding protein beta

• Published in: Cancer research (Chicago, Ill.) Vol. 63; no. 7; pp. 1696 - 1705
• Main Authors: Kagan, Benjamin L, Henke, Ralf T, Cabal-Manzano, Rafael, Stoica, Gerald E, Nguyen, Quang, Wellstein, Anton, Riegel, Anna Tate
• Format: Journal Article
• Language: English
• Published: United States 01.04.2003
• Subjects: Binding Sites; Breast Neoplasms - enzymology; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Breast Neoplasms - pathology; C/EBP^b protein; Carrier Proteins - biosynthesis; Carrier Proteins - genetics; CCAAT-Enhancer-Binding Protein-beta - physiology; Epidermal Growth Factor - pharmacology; Epidermal Growth Factor - physiology; fibroblast growth factor-binding protein; Gene Expression Regulation, Neoplastic - drug effects; Gene Expression Regulation, Neoplastic - physiology; MAP Kinase Signaling System - drug effects; MAP Kinase Signaling System - physiology; Mitogen-Activated Protein Kinases - metabolism; Neoplasm Invasiveness; p38 Mitogen-Activated Protein Kinases; Promoter Regions, Genetic; Protein Kinase C - metabolism; RNA, Messenger - biosynthesis; RNA, Messenger - genetics; Transcription Factor AP-1 - metabolism; Transfection; Tumor Cells, Cultured
• ISSN: 0008-5472

The fibroblast growth factor-binding protein (FGF-BP) binds and activates fibroblast growth factors in the extracellular matrix, and can have a rate-limiting role in tumor angiogenesis. Here we demonstrate high levels of FGF-BP expression in invasive human breast cancer, relative to normal breast and in situ carcinoma, and in MDA-MB-468 human breast cancer cells. In these cells, FGF-BP was up-regulated by treatment with epidermal growth factor (EGF), dependent on protein kinase C and p38 mitogen-activated protein kinase signaling. Mutational analysis revealed that the activator protein 1 and CCAAT/enhancer binding protein (C/EBP) sites on the FGF-BP gene promoter were required for the EGF effect, whereas deletion of the C/EBP site resulted in a significant increase in promoter basal activity indicating a basal repressive control mechanism. These data suggest that the C/EBP site is a central regulatory element for the regulation of FGF-BP promoter activity in MDA-MB-468 cells. We found that MDA-MB-468 cells express high endogenous levels of both the activating (LAP) and repressive (LIP) isoforms of C/EBPbeta. Overexpression of C/EBPbeta-LAP in MDA-MB-468 cells resulted in a large 80-fold increase in FGF-BP promoter basal activity, which was reversed by coexpression of LIP. Gel-shift analysis revealed that four LIP- and LAP-containing complexes (a-d) bind to the C/EBP site. DNA binding of the LIP and LAP-containing c complex and the b complex in the presence of EGF was modulated by inhibition of p38 mitogen-activated protein kinase, suggesting a role for these complexes in the EGF induction of the FGF-BP promoter. This study suggests that along with its well-defined role in mammary gland development, C/EBPbeta may well play a role in the pathology of breast cancer, in particular in the control of angiogenesis in the invasive phenotype.