Open Access Research article

Aberrant methylation of Polo-like kinase CpG islands in Plk4 heterozygous mice

Alejandra Ward1, Alan Morettin1, David Shum2 and John W Hudson1*

Author Affiliations

1 University of Windsor, Department of Biological Sciences, 401 Sunset Avenue, Windsor, Ontario, N9B 3P4, Canada

2 Windsor Regional Hospital, Metropolitan Campus, Department of Pathology, 1995 Lens Ave, Windsor, Ontario, N8W 1L9, Canada

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BMC Cancer 2011, 11:71  doi:10.1186/1471-2407-11-71

Published: 15 February 2011

Abstract

Background

Hepatocellular carcinoma (HCC), one of the most common cancers world-wide occurs twice as often in men compared to women. Predisposing conditions such as alcoholism, chronic viral hepatitis, aflatoxin B1 ingestion, and cirrhosis all contribute to the development of HCC.

Methods

We used a combination of methylation specific PCR and bisulfite sequencing, qReal-Time PCR (qPCR), and Western blot analysis to examine epigenetic changes for the Polo-like kinases (Plks) during the development of hepatocellular carcinoma (HCC) in Plk4 heterozygous mice and murine embryonic fibroblasts (MEFs).

Results

Here we report that the promoter methylation of Plk4 CpG islands increases with age, was more prevalent in males and that Plk4 epigenetic modification and subsequent downregulation of expression was associated with the development of HCC in Plk4 mutant mice. Interestingly, the opposite occurs with another Plk family member, Plk1 which was typically hypermethylated in normal liver tissue but became hypomethylated and upregulated in liver tumours. Furthermore, upon alcohol exposure murine embryonic fibroblasts exhibited increased Plk4 hypermethylation and downregulation along with increased centrosome numbers and multinucleation.

Conclusions

These results suggest that aberrant Plk methylation is correlated with the development of HCC in mice.