Mitochondrial regulation of cancer associated nuclear DNA methylation

doi:10.1016/j.bbrc.2007.10.047

Biochemical and Biophysical Research Communications

Volume 364, Issue 3, 21 December 2007, Pages 656-661

https://doi.org/10.1016/j.bbrc.2007.10.047 Get rights and content

Abstract

The onset and progression of cancer is associated with the methylation-dependent silencing of specific genes, however, the mechanism and its regulation have not been established. We previously demonstrated that reduction of mitochondrial DNA content induces cancer progression. Here we found that mitochondrial DNA-deficient LNρ0-8 activates the hypermethylation of the nuclear DNA promoters including the promoter CpG islands of the endothelin B receptor, O⁶-methylguanine-DNA methyltransferase, and E-cadherin. These are unmethylated and the corresponding gene products are expressed in the parental LNCaP containing mitochondrial DNA. The absence of mitochondrial DNA induced DNA methyltransferase 1 expression which was responsible for the methylation patterns observed. Inhibition of DNA methyltransferase eliminated hypermethylation and expressed gene products in LNρ0-8. These studies demonstrate loss or reduction of mitochondrial DNA resulted in the induction of DNA methyltransferase 1, hypermethylation of the promoters of endothelin B receptor, O⁶-methylguanine-DNA methyltransferase, and E-cadherin, and reduction of the corresponding gene products.

Section snippets

Materials and methods

Materials and cell culture. Details of materials and cell culture methods are provided in Supplementary information.

Genomic DNA extraction and methylation analysis. Details of Genomic DNA extraction and methylation analysis methods are provided in Supplementary information (Table 2).

Western blotting. Details of Western blotting methods are provided in Supplementary information.

Determination of mtDNA copy number using real-time quantitative PCR. Details of determination of mtDNA copy number

Depleting mtDNA induces promoter CpG island hypermethylation

We first investigated whether depletion of mtDNA induces promoter CpG island hypermethylation in LNρ0-8. This cell line lacks mtDNA and was established from early-stage human prostate cancer cell line LNCaP[6]. The methylation status of the target genes (i.e., EDNRB, CDH-1, and MGMT) was analyzed using the methylation-specific PCR (MSP) technique. We observed that the EDNRB promoter CpG island in LNρ0-8 cells was completely methylated, yet in LNCaP cells this island was unmethylated (Fig. 1A).

Discussion

Our study provides the first evidence that mtDNA content contributes to regulating hypermethylation of promoter CpG islands. Both of the mtDNA-deficient cell lines (i.e., LNρ0-8 and MCFρ0) established from prostate cancer cell line LNCaP and the breast cancer cell line MCF-7 showed increase in the hypermethylation of promoter CpG islands of EDNRB, MGMT, and CDH-1. Overall, a reduction of mtDNA content induced hypermethylation, and recovery of mtDNA reduced hypermethylation. We also demonstrate

Acknowledgments

We would like to express our gratitude to Dr. Thomas J. Kelly for his advice during preparation of the manuscript. We also thank Mrs. Margaret E. Brenner for reviewing the manuscript. This work was supported by Taiho Pharmaceutical Co. Ltd, Tobacco Settlement at State of Arkansas and NIH Grant CA100846 to M.H.

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Mitochondrial regulation of cancer associated nuclear DNA methylation

Abstract

Section snippets

Materials and methods

Depleting mtDNA induces promoter CpG island hypermethylation

Discussion

Acknowledgments

FEBS Letters

Human Pathology

Cell

Blood

Cancer statistics

CA Cancer Journal for Clinicians

Epigenetic changes in prostate cancer: implication for diagnosis and treatment

Journal of the National Cancer Institute

Abnormal patterns of DNA methylation in human neoplasia: potential consequences for tumor progression

Cancer Cells

Human cells lacking mtDNA: repopulation with exogenous mitochondria by complementation

Science

Mitochondrial DNA determines androgen dependence in prostate cancer cell lines

Oncogene

The cadherin cell–cell adhesion pathway in prostate cancer progression

British Journal of Urology