title: Connexin26 regulates the expression of angiogenesis-related genes in human breast tumor cells by both GJIC-dependent and -independent mechanisms.
abstract: We previously reported that over-expression of connexins in mammary tumor cells retarded tumor growth in vivo in the absence of appreciable gap junction formation, highlighting a possible connexin-linked, but gap junctional intercellular communication (GJIC)-independent mechanism. In the current study, we engineered GJIC-deficient MDA-MB-435 human breast tumor cells to express a chimeric Cx26 where the green fluorescent protein was fused to the amino-terminal of Cx26 (GFP-Cx26). Characterization of this chimeric protein revealed that GFP-Cx26 assembled into non-functional gap junction-like clusters that were impermeable to Lucifer Yellow. In contrast, expression of wild-type Cx26 or Cx26 tagged at the carboxy terminal with yellow fluorescent protein, efficiently rescued GJIC in these tumor cells. Interestingly, by screening 96 tumor-related genes, we observed that the expression of Cx26 or GFP-Cx26 in the tumor cells up-regulated both the transcription and the translation of thrombospondin-1 (TSP-1), an anti-angiogenic molecule. Affymetrix array analysis extended the list of Cx26 or GFP-Cx26 regulated genes by ten candidates including connective tissue growth factor (CTGF), another angiogenesis-related gene. CTGF mRNA and protein levels were found to be down-regulated by both Cx26 and GFP-Cx26. Thus, our data indicates that Cx26 regulates angiogenesis-related molecules by mechanisms that are both GJIC-dependent and -independent.
authors.affiliation: Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Hong
authors.initials: H
authors.lastname: Qin
authors.forename: Qing
authors.initials: Q
authors.lastname: Shao
authors.forename: Tamsin
authors.initials: T
authors.lastname: Thomas
authors.forename: Jessica
authors.initials: J
authors.lastname: Kalra
authors.forename: Moulay A
authors.initials: MA
authors.lastname: Alaoui-Jamali
authors.forename: Dale W
authors.initials: DW
authors.lastname: Laird
mesh_terms: D055513:Connective Tissue Growth Factor; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D020869:Gene Expression Profiling; D049452:Green Fluorescent Proteins; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D007365:Intercellular Junctions / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D008164:Luminescent Proteins / Q000378:metabolism; D009389:Neovascularization, Pathologic / Q000378:metabolism*; D015398:Signal Transduction; D019700:Thrombospondin 1 / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: C526317:CCN2 protein, human; D017630:Connexins; C000607042:GJB2 protein, human; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D019700:Thrombospondin 1; D000072259:Connexin 26; D055513:Connective Tissue Growth Factor; D049452:Green Fluorescent Proteins