High-resistance MDCK-C7 monolayers used for measuring invasive potency of tumour cells

We describe an electrophysiological method for evaluating the intrinsic invasive potency of tumour cells using renal cells as an in vitro assay system. A high-resistance clone of Madin-Darby canine kidney cells (MDCK-C7) was grown to confluency in a filter cup. Transepithelial electrical resistance across the MDCK-C7 monolayer was measured in a commercially available electrode chamber. After a transepithelial electrical resistance of about 4,000 Omega cm(2) had been reached, human melanoma or pancreatic carcinoma cells were cocultivated with the MDCK-C7 monolayer. Both carcinoma cell lines induced resistance breakdown measured after 24 h or later depending on seeding density and cell type. Seeding carcinoma cells on the basolateral surface of MDCK-C7 cells caused a similar decrease in transepithelial resistance of the MDCK-C7 monolayer. Resistance breakdown indicates opening of tight junctions prior to tumour cell invasion. In conclusion, the high-resistance MDCK-C7 cell clone could serve as a valuable biological assay system to determine electrically the metastatic potency of tumour cells in vitro.