Acta Pharmacologica Sinica (2010) 31: 202–210; doi: 10.1038/aps.2009.200

Acta Pharmacologica Sinica (2010) 31: 202–210; doi: 10.1038/aps.2009.200

Original Article

Downregulation of Dickkopf-1 is responsible for high proliferation of breast cancer cells via losing control of Wnt/β-catenin signaling

Xiao-lei ZHOU¹, Xiao-ran QIN¹, Xiao-dong ZHANG^{2, *}, Li-hong YE^{1, *}

Departments of ¹Biochemistry and ²Cancer Research, Key Laboratory of Molecular Microbiology and Technology of Ministry of Education, Institute for Molecular Biology, College of Life Sciences, Nankai University, Tianjin 300071, China

Aim: To investigate the role of DKK-1/Wnt/β-catenin signaling in high proliferation of LM-MCF-7 breast cancer cells, a sub-clone of MCF-7 cell line.

Methods: Two cell lines (MCF-7 and LM-MCF-7) with different proliferation abilities were used. LM-MCF-7 cells were transiently transfected with the pcDNA3-DKK-1 plasmid encoding the DKK-1 gene (or MCF-7 cells were transfected siRNA targeting DKK-1 mRNA). Flow cytometry analysis and 5-bromo-2′-deoxyuridine (BrdU) incorporation assay were applied to detect the cell proliferation. The expression levels of β-catenin, phosphorylated β-catenin, c-Myc, cyclin D1 and Survivin were examined by Western blot analysis. The regulation of Survivin was investigated by Luciferase reporter gene assay.

Results: Western blot and RT-PCR analysis showed that the expression level of DKK-1 was downregulated in LM-MCF-7 relative to MCF-7 cells. Flow cytometry and BrdU incorporation assay showed DKK-1 could suppress growth of breast cancer cells. Overexpression of DKK-1 was able to accelerate phosphorylation-dependent degradation of β-catenin and downregulate the expression of β-catenin, c-Myc, cyclin D1 and Survivin. Luciferase reporter gene assay demonstrated that Survivin could be regulated by β-catenin/TCF4 pathway.

Conclusion: We conclude that the downregulation of DKK-1 is responsible for the high proliferation ability of LM-MCF-7 breast cancer cells via losing control of Wnt/β-catenin signaling pathway, in which c-Myc, cyclinD1 and Survivin serve as essential downstream effectors. Our finding provides a new insight into the mechanism of breast cancer cell proliferation.

Keywords: Dickkopf-1; Wnt/β-catenin; breast cancer; cell proliferation; MCF-7 cell line; survivin

We thank Prof VJ HEARING from the Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, USA, for providing pcDNA3-DKK-1 plasmid. The project was supported by grants of National Basic Research Program of China (973 Program, No 2007CB914802, No 2007CB914804, No 2009CB521702), National Natural Scientific Foundation (No 30770826), and Tianjin Natural Scientific Foundation (No 08JCZDJC20700).

* To whom correspondence should be addressed.
E-mail yelihong@nankai.edu.cn (Prof Li-hong YE);
zhangxd@nankai.edu.cn (Prof Xiao-dong ZHANG)
Received 2009-10-22 Accepted 2009-12-22

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