Analysis of Promoter Non-CG Methylation in Prostate Cancer

Abstract

Background: In vertebrates, DNA methylation occurs primarily at CG dinucleotides but recently, non-CG methylation has been found at appreciable levels in embryonic stem cells. Materials & methods: To assess non-CG methylation in cancer, we compared the extent of non-CG methylation at several biologically important CG islands in prostate cancer and normal cell lines. An assessment of the promoter CG islands EVX1 and FILIP1L demonstrates a fourfold higher rate of non-CG methylation at EVX1 compared with FILIP1L across all cell lines. These loci are densely methylated at CG sites in cancer. Results: No significant difference in non-CG methylation was demonstrated between cancer and normal. Treatment of cancer cell lines with 5-azacytidine significantly reduced methylation within EVX1 at CG and CC sites, preferentially. Conclusion: Non-CG methylation does not correlate with CG methylation at hypermethylated promoter regions in cancer. Furthermore, global inhibition of DNA methyltransferases does not affect all methylated cytosines uniformly.

Keywords::

• 5-azacytidine
• epigenetics
• EVX1
• non-CG methylation
• prostate cancer

Financial & competing interests disclosure

This study was supported by NIH 5RO1CA 097131 and the Livesey Endowment. M Truong was funded by the Institute for Clinical and Translational Research Training Grant for Medical Students (NIH KL2 RR02012). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Additional information

Funding

This study was supported by NIH 5RO1CA 097131 and the Livesey Endowment. M Truong was funded by the Institute for Clinical and Translational Research Training Grant for Medical Students (NIH KL2 RR02012). The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.