title: Cx26 inhibits breast MDA-MB-435 cell tumorigenic properties by a gap junctional intercellular communication-independent mechanism.
abstract: It has been well established that the restoration of connexin expression in tumor cells often leads to a partial reversion of tumor cell phenotypes and increased growth control. In this study, a less-aggressive variant of MDA-MB-435 cells obtained from the MDA-MB-435 cell line was engineered to express gap junctional intercellular communication (GJIC)-competent Cx26, a GJIC-incompetent cell surface transported GFP-Cx26 chimera, or a Golgi apparatus-localized, disease-linked Cx26 mutant (D66H). Collectively, these cell lines were designed to establish whether Cx26 regulates tumor properties, such as migration, invasion and growth, by (i) a GJIC-dependent pathway; (ii) a mechanism requiring Cx26 transport to the cell surface; or (iii) a mechanism where Cx26 expression alone was sufficient. The expression of Cx26 and green fluorescent protein (GFP)-Cx26 decreased cell proliferation while all three Cx26 variants inhibited anchorage-independent cell growth. All three Cx26 variants also altered the distribution of filamentous actin and significantly reduced cell migration, while only the D66H mutant failed to inhibit cell invasion through matrigel. Furthermore, expression of all the Cx26 variants reduced the levels of total beta1 integrin, and decreased the activity of matrix metalloproteinase-9 (MMP-9) while increasing tissue inhibitors of MMP-1 (TIMP-1) activity. Interestingly, the expression of Cx43 regulated the same gene products without significantly affecting the tumorigenic properties of the MDA-MB-435 cells. Together, these results suggest that Cx26 expression, independent of the necessity for gap junctional intercellular communication, partially reverted MDA-MB-435 cell properties associated with tumorigenesis, and regulated the expression of genes important in cell migration and invasion.
authors.affiliation: Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario, Canada N6A 5C1.
authors.forename: Jessica
authors.initials: J
authors.lastname: Kalra
authors.forename: Qing
authors.initials: Q
authors.lastname: Shao
authors.forename: Hong
authors.initials: H
authors.lastname: Qin
authors.forename: Tamsin
authors.initials: T
authors.lastname: Thomas
authors.forename: Moulay A
authors.initials: MA
authors.lastname: Alaoui-Jamali
authors.forename: Dale W
authors.initials: DW
authors.lastname: Laird
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000473:pathology / Q000517:prevention & control*; D002450:Cell Communication; D002455:Cell Division; D002460:Cell Line; D045744:Cell Line, Tumor; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D005260:Female; D017629:Gap Junctions / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D014644:Genetic Variation; D006801:Humans; D018613:Microscopy, Confocal; D009361:Neoplasm Invasiveness; D051381:Rats
chemical_list: D017630:Connexins; C000607042:GJB2 protein, human; C000607044:Gjb2 protein, rat; D000072259:Connexin 26