Association of 5-Methylcytosine and 5-Hydroxymethylcytosine with Mitochondrial DNA Content and Clinical and Biochemical Parameters in Hepatocellular Carcinoma

Abstract

Increasing epidemiological evidence has indicated that inherited variations of mitochondrial DNA (mtDNA) copy number affect the genetic susceptibility of many malignancies in a tumour-specific manner and that DNA methylation also plays an important role in controlling gene expression during the differentiation and development of hepatocellular carcinoma (HCC). Our previous study demonstrated that HCC tissues showed a lower 5-hydroxymethylcytosine (5-hmC) content when compared to tumour-adjacent tissues, but the relationship among 5-hmC, 5-methylcytosine (5-mC) and mtDNA content in HCC patients is still unknown. This study aimed to clarify the correlation among mtDNA content, 5-mC and 5-hmC by quantitative real-time PCR and liquid chromatography tandem mass spectrometry analysis. We demonstrated that 5-hmC correlated with tumour size [odds ratio (OR) 0.847, 95% confidence interval (CI) 0.746–0.962, P = 0.011], and HCC patients with a tumour size ≥5.0 cm showed a lower 5-hmC content and higher levels of fasting plasma aspartate aminotransferase, the ratio of alanine amiotransferase to aspartate aminotransferase, γ-glutamyltransferase, alpha-fetoprotein than those with a tumour size <5 cm (all P<0.05). We further revealed that the mtDNA content of HCC tumour tissues was 225.97(105.42, 430.54) [median (25th Percentile, 75th Percentile)] and was negatively correlated with 5-mC content (P = 0.035), but not 5-hmC content, in genomic DNA from HCC tumour tissues.

Association of global DNA hypomethylation with clinicopathological variables in colonic tumors of Iraqi patients

“…[ 29 ] The present study revealed that 5mC immunohistochemical expression is significantly lower in adenomas measuring 1 cm or more, and those with severe dysplastic change. The mean value of 5mC was inversely correlated with increasing morphologic dysplasia in adenomas (mild, moderate, and severe), which is comparable with a recent study conducted by Shen et al[ 30 ] There was no significant difference in 5mC immunohistochemical expression according to histopathological types of adenomas (tubular, villous, and tubulovillous) and other clinicopathological parameters, including age, gender, and site, which agrees with a previous study by Bariol et al[ 22 ]…”

“…The present research reported nonsignificant correlation between 5mC immunohistochemical expression with age, gender, site grade, and histopathological types of colorectal carcinoma; this is equivalent with other studies. [ 22 30 ] There was significant correlation between 5mC immunohistochemical expression with stage of carcinoma, which agrees with recent articles. [ 30 32 ]…”

The mitochondrial side of epigenetics

“…At present it is not known whether mtDNA methylation is subjected to reprogramming during embryogenesis as nDNA. However, the dynamic mtDNA methylation patterns associated with aging (17), environmental stimuli (13,87), and diseases (45,84) highlight the possibility that remodeling of mtDNA methylation could occur through a rapid methylation/ demethylation turnover. This is also supported by very interesting findings on the role of pharmaceuticals such as valproic acid in modulating mitochondrial epigenetics (18).…”

Plasma mtDNA copy numbers are associated with GSTK1 expression and inflammation in type 2 diabetes

“…Determination of mtDNA copy numbers and GSTK1 expression A quantitative polymerase chain reaction (qPCR) that simultaneously targeted a single-copy nuclear gene (b2microglobulin, b 2 M) and the tRNA Leu (UUR) gene on the mtDNA was used to quantify mtDNA copy numbers [12][13][14]. GSTK1 expression (mRNA) was quantified and normalized by b-ACTIN and GAPDH.…”