Open Access Highly Accessed Research article

Anti-apoptotic effect of claudin-1 in tamoxifen-treated human breast cancer MCF-7 cells

Harue Akasaka1, Fuyuki Sato1*, Satoko Morohashi1, Yunyan Wu12, Yang Liu12, Jun Kondo1, Hiroki Odagiri3, Kenichi Hakamada3 and Hiroshi Kijima1

Author Affiliations

1 Department of Pathology and Bioscience, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan

2 Department of Pathology, College of Basic Medical Sciences, China Medical University, Shenyang, 110001, China

3 Department of Surgery, Hirosaki University Graduate School of Medicine, Hirosaki 036-8562, Japan

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BMC Cancer 2010, 10:548  doi:10.1186/1471-2407-10-548

Published: 12 October 2010

Abstract

Background

Claudin-1 is a membrane protein of tight junctions, and is associated with the development of various cancers. However, the significance of claudin-1 expression in cancer cells is not well understood. Here, we showed for the first time the anti-apoptotic effect of claudin-1 in human breast cancer MCF-7 cells.

Methods

Human breast cancer MCF-7 and T47 D cells were treated with or without tamoxifen, siRNA against claudin-1, or tamoxifen and claudin-1 siRNA. The samples were analyzed by RT-PCR, Western blotting or immunofluorescent staining.

Results

The expression of claudin-1 was upregulated in tamoxifen-treated MCF-7 cells, whereas the expression of claudin-1 was not altered in tamoxifen-treated T47 D cells. Knockdown of claudin-1 by siRNA increased the amount of poly (ADP-ribose) polymerase (PARP) regardless of tamoxifen treatment in MCF-7 cells, but not T47 D cells. In the cell membranes of the MCF-7 cells, tamoxifen treatment increased the amount of claudin-1, but decreased the amount of β-catenin. Claudin-1 siRNA increased the amount of E-cadherin in the cytoplasm of the MCF-7 cells as well as the amount of β-catenin in their cell membranes.

Conclusion

These results indicate that claudin-1 has anti-apoptotic effects, and is involved in the regulation of the expression and subcellular localization of β-catenin and E-cadherin in MCF-7, but not T47 D cells.