BACKGROUNDClaudin-6 is a protein component of tight junctions and its expression could downregulate the malignant phenotype of breast carcinoma. Here we investigated the mechanisms of claudin-6 induced human MCF-7 breast cancer cells apoptosis, invasion, and migration.

METHODSTerminal deoxyribonucleotide transferase-mediated nick-end labeling assay and Annexin-V/PI double stain assay were carried out to evaluate apoptosis. Inhibitors of each pathway were used to inactivate the signaling pathways. The expression of claudin-6 and phosphate p38, Erk 1/2 and Akt protein levels was confirmed by Western blotting analysis. Invasive and migratory traits of claudin-6 expressing cells were determined by Boyden chamber invasion assay and monolayer wound-healing assay.

RESULTSCells with high-level expression of claudin-6 had a higher rate of apoptosis than control cells. Western blotting assay showed that by contrast to control groups, p38 pathways were more activated in claudin-6 expressing cells. However, after inhibitor SB203580 treatment, the activation status could be significantly counteracted. Furthermore, by applying inhibitors to the apoptotic rate, invasive and migratory traits were also recovered in cells with claudin-6 expression.

CONCLUSIONClaudin-6 may function through p38 mitogen-activated protein kinase pathway, of which inhibition may reverse claudin-6-induced cell apoptosis, invasion, and migration.