Connexin 43 mediated gap junctional communication enhances breast tumor cell diapedesis in culture.
BACKGROUND
Metastasis involves the emigration of tumor cells through the vascular endothelium, a process also known as diapedesis. The molecular mechanisms regulating tumor cell diapedesis are poorly understood, but may involve heterocellular gap junctional intercellular communication (GJIC) between tumor cells and endothelial cells.


METHODS
To test this hypothesis we expressed connexin 43 (Cx43) in GJIC-deficient mammary epithelial tumor cells (HBL100) and examined their ability to form gap junctions, establish heterocellular GJIC and migrate through monolayers of human microvascular endothelial cells (HMVEC) grown on matrigel-coated coverslips.


RESULTS
HBL100 cells expressing Cx43 formed functional heterocellular gap junctions with HMVEC monolayers within 30 minutes. In addition, immunocytochemistry revealed Cx43 localized to contact sites between Cx43 expressing tumor cells and endothelial cells. Quantitative analysis of diapedesis revealed a two-fold increase in diapedesis of Cx43 expressing cells compared to empty vector control cells. The expression of a functionally inactive Cx43 chimeric protein in HBL100 cells failed to increase migration efficiency, suggesting that the observed up-regulation of diapedesis in Cx43 expressing cells required heterocellular GJIC. This finding is further supported by the observation that blocking homocellular and heterocellular GJIC with carbenoxolone in co-cultures also reduced diapedesis of Cx43 expressing HBL100 tumor cells.


CONCLUSIONS
Collectively, our results suggest that heterocellular GJIC between breast tumor cells and endothelial cells may be an important regulatory step during metastasis.
Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, Canada. mpollman@uwo.ca
Mary-Ann
MA
Pollmann
Qing
Q
Shao
Dale W
DW
Laird
Martin
M
Sandig
D001943:Breast Neoplasms / Q000473:pathology*; D002450:Cell Communication; D002465:Cell Movement / Q000502:physiology*; D018031:Connexin 43 / Q000502:physiology*; D004730:Endothelium, Vascular; D005260:Female; D017629:Gap Junctions; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology; D009362:Neoplasm Metastasis / Q000503:physiopathology; D014407:Tumor Cells, Cultured
D018031:Connexin 43; C500216:GJA1 protein, human