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Effect of tight junctional resistance on penetration of LLC-PK1 epithelial cell layers by metastatic B16-F10 melanoma cells.

The relationship between tight junctional resistance of a tissue and its penetration by metastatic cells was examined in vitro using LLC-PK1 cells, an epithelial cell line derived from pig kidney, and B16-F10 cells, a murine melanoma cell line metastatic in syngeneic C57BL/6 mice. When grown to confluence on 8.0-microns pore size polycarbonate filters, LLC-PK1 cells formed tight junctions between adjacent cells which offered an electrical resistance to a nondestructive 20-mu ampere alternating current passed across the cell layer. B16-F10 cells seeded on top of an LLC-PK1 epithelial layer with a measured transepithelial resistance of approximately 300 omega x cm2 were unable to penetrate the epithelial barrier. The tumor-promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) lowered the electrical resistance of the epithelial layer by 80% and simultaneously opened the epithelial barrier to penetration by metastatic cells.