title: TGF-β Negatively Regulates CXCL1 Chemokine Expression in Mammary Fibroblasts through Enhancement of Smad2/3 and Suppression of HGF/c-Met Signaling Mechanisms.
abstract: Fibroblasts are major cellular components of the breast cancer stroma, and influence the growth, survival and invasion of epithelial cells. Compared to normal tissue fibroblasts, carcinoma associated fibroblasts (CAFs) show increased expression of numerous soluble factors including growth factors and cytokines. However, the mechanisms regulating expression of these factors remain poorly understood. Recent studies have shown that breast CAFs overexpress the chemokine CXCL1, a key regulator of tumor invasion and chemo-resistance. Increased expression of CXCL1 in CAFs correlated with poor patient prognosis, and was associated with decreased expression of TGF-β signaling components. The goal of these studies was to understand the role of TGF-β in regulating CXCL1 expression in CAFs, using cell culture and biochemical approaches. We found that TGF-β treatment decreased CXCL1 expression in CAFs, through Smad2/3 dependent mechanisms. Chromatin immunoprecipitation and site-directed mutagenesis assays revealed two new binding sites in the CXCL1 promoter important for Smad2/3 modulation of CXCL1 expression. Smad2/3 proteins also negatively regulated expression of Hepatocyte Growth Factor (HGF), which was found to positively regulate CXCL1 expression in CAFs through c-Met receptor dependent mechanisms. HGF/c-Met signaling in CAFs was required for activity of NF-κB, a transcriptional activator of CXCL1 expression. These studies indicate that TGF-β negatively regulates CXCL1 expression in CAFs through Smad2/3 binding to the promoter, and through suppression of HGF/c-Met autocrine signaling. These studies reveal novel insight into how TGF-β and HGF, key tumor promoting factors modulate CXCL1 chemokine expression in CAFs.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, United States of America.
authors.forename: Wei Bin
authors.initials: WB
authors.lastname: Fang
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, United States of America.
authors.forename: Benford
authors.initials: B
authors.lastname: Mafuvadze
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, United States of America.
authors.forename: Min
authors.initials: M
authors.lastname: Yao
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, United States of America.
authors.forename: An
authors.initials: A
authors.lastname: Zou
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, United States of America.
authors.forename: Mike
authors.initials: M
authors.lastname: Portsche
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS, United States of America.
authors.forename: Nikki
authors.initials: N
authors.lastname: Cheng
mesh_terms: D000818:Animals; D001940:Breast / Q000378:metabolism / Q000473:pathology; D018270:Carcinoma, Ductal, Breast / Q000378:metabolism / Q000473:pathology; D054360:Chemokine CXCL1 / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D006801:Humans; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
chemical_list: C475829:CXCL1 protein, human; D054360:Chemokine CXCL1; C475895:Cxcl1 protein, mouse; D034741:RNA, Small Interfering; D051899:Smad2 Protein; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met