Over-expression of transferrin receptor 1 (TFRC) is observed in hepatocellular carcinoma (HCC); however, there is a lack of conclusive information regarding the mechanisms of this dysregulation. In ...the present study, we demonstrated a significant increase in the levels of TFRC mRNA and protein in preneoplastic livers from relevant experimental models of human hepatocarcinogenesis and in human HCC cells. Additionally, using the TCGA database, we demonstrated an over-expression of TFRC in human HCC tissue samples and a markedly decreased level of microRNA-152 (miR-152) when compared to non-tumor liver tissue. The results indicated that the increase in levels of TFRC in human HCC cells and human HCC tissue samples may be attributed, in part, to a post-transcriptional mechanism mediated by a down-regulation of miR-152. This was evidenced by a strong inverse correlation between the level of TFRC and the expression of miR-152 in human HCC cells (r = -0.99, p = 4. 7 × 10-9), and was confirmed by in vitro experiments showing that transfection of human HCC cell lines with miR-152 effectively suppressed TFRC expression. This suggests that miR-152-specific targeting of TFRC may provide a selective anticancer therapeutic approach for the treatment of HCC.
The substantial rise in the prevalence of nonalcoholic steatohepatitis (NASH), an advanced form of nonalcoholic fatty liver disease, and the strong association between NASH and the development of ...hepatocellular carcinoma indicate the urgent need for a better understanding of the underlying mechanisms. In the present study, by using the Stelic animal model of NASH and NASH‐derived liver carcinogenesis, we investigated the role of the folate‐dependent 1‐carbon metabolism in the pathogenesis of NASH. We demonstrated that advanced NASH and NASH‐related liver carcinogenesis are characterized by a significant dysregulation of 1‐carbon homeostasis, with diminished expression of key 1‐carbon metabolism genes, especially a marked inhibition of the S‐adenosylhomocysteine hydrolase (Ahcy) gene and an increased level of S‐adenosyl‐L‐homocysteine (SAH). The reduction in Ahcy expression was associated with gene‐specific cytosine DNA hypermethylation and enrichment of the gene promoter by trimethylated histone H3 lysine 27 and deacetylated histone H4 lysine 16, 2 main transcription‐inhibiting markers. These results indicate that epigenetically mediated inhibition of Ahcy expression may be a driving force in causing SAH elevation and subsequent downstream disturbances in transsulfuration and transmethylation pathways during the development and progression of NASH.—Pogribny, I. P., Dreval, K., Kindrat, I., Melnyk, S., Jimenez, L., de Conti, A., Tryndyak, V., Pogribna, M., Ortega, J. F., James, S. J., Rusyn, I., Beland, F. A. Epigenetically mediated inhibition of S‐adenosylhomocysteine hydrolase and the associated dysregulation of 1‐carbon metabolism in nonalcoholic steatohepatitis and hepatocellular carcinoma. FASEB J. 32,1591‐1601 (2018). www.fasebj.org
Interindividual variability and sexual dimorphisms in the development of nonalcoholic fatty liver disease (NAFLD) are still poorly understood. In the present study, male and female strains of ...Collaborative Cross (CC) mice were fed a high‐fat and high‐sucrose (HF/HS) diet or a control diet for 12 weeks to investigate interindividual‐ and sex‐specific variations in the development of NAFLD. The severity of liver steatosis varied between sexes and individual strains and was accompanied by an elevation of serum markers of insulin resistance, including increases in total cholesterol, low‐density lipoproteins, high‐density lipoproteins, phospholipids, and glucose. The development of NAFLD was associated with overexpression of the critical fatty acid uptake and de novo lipogenesis genes Pparg, Mogat1, Cd36, Acaab1, Fabp2, and Gdf15 in male and female mice. The expression of Pparg, Mogat1, and Cd36 was positively correlated with liver triglycerides in male mice, and Mogat1 and Cd36 expression were positively correlated with liver triglycerides in female mice. Our results indicate the value of CC mice in combination with HF/HS diet‐induced alterations as an approach to study the susceptibility and interindividual variabilities in the pathogenesis of nonalcoholic fatty liver and early nonalcoholic steatohepatitis at the population level, uncovering of susceptible and resistant cohorts, and identifying sex‐specific molecular determinants of disease susceptibility.
Hepatocellular carcinoma (HCC) is one of the most aggressive human cancers, and its incidence is steadily increasing worldwide. Recent epidemiologic findings have suggested that the increased ...incidence of HCC is associated with obesity, type II diabetes mellitus, and nonalcoholic steatohepatitis (NASH); however, the mechanisms and the molecular pathogenesis of NASH-related HCC are not fully understood. To elucidate the underlying mechanisms of the development of NASH-related HCC, we investigated the hepatic transcriptomic and histone modification profiles in Stelic Animal Model mice, the first animal model of NASH-related HCC to resemble the disease pathogenesis in humans. The results demonstrate that the development of NASH-related HCC is characterized by progressive transcriptomic alterations, global loss of histone H4 lysine 20 trimethylation (H4K20me3), and global and gene-specific deacetylation of histone H4 lysine 16 (H4K16). Pathway analysis of the entire set of differentially expressed genes indicated that the inhibition of cell death pathway was the most prominent alteration, and this was facilitated by persistent gene-specific histone H4K16 deacetylation. Mechanistically, deacetylation of histone H4K16 was associated with downregulation of lysine acetyltransferase KAT8, which was driven by overexpression of its inhibitor nuclear protein 1 (
). The results of this study identified a reduction of global and gene-specific histone H4K16 acetylation as a key pathophysiologic mechanism contributing to the development of NASH-derived HCC and emphasized the importance of epigenetic alterations as diagnostic and therapeutic targets for HCC.
Histone H4K16 deacetylation induces silencing of genes related to the cell death that occurred during the development of NASH-related HCC.
.
The presence of furan in common cooked foods along with evidence from experimental studies that lifetime exposure to furan causes liver tumors in rats and mice has caused concern to regulatory public ...health agencies worldwide; however, the mechanisms of the furan-induced hepatocarcinogenicity remain unclear. The goal of the present study was to investigate whether or not long-term exposure to furan causes epigenetic alterations in rat liver. Treating of male Fisher 344 rats by gavage 5 days per week with 0, 0.92, 2.0, or 4.4 mg furan/kg body weight (bw)/day resulted in dose- and time-dependent epigenetic changes consisting of alterations in DNA methylation and histone lysine methylation and acetylation, altered expression of chromatin modifying genes, and gene-specific methylation. Specifically, exposure to furan at doses 0.92, 2.0, or 4.4 mg furan/kg bw/day caused global DNA demethylation after 360 days of treatment. There was also a sustained decrease in the levels of histone H3 lysine 9 and H4 lysine 20 trimethylation after 180 and 360 days of furan exposure, and a marked reduction of histone H3 lysine 9 and H3 lysine 56 acetylation after 360 days at 4.4 mg/kg bw/day. These histone modification changes were accompanied by a reduced expression of Suv39h1, Prdm2, and Suv4-20h2 histone methyltransferases and Ep300 and Kat2a histone acetyltransferases. Additionally, furan at 2.0 and 4.4 mg/kg bw/day induced hypermethylation-dependent down-regulation of the Rassf1a gene in the livers after 180 and 360 days. These findings indicate possible involvement of dose- and time-dependent epigenetic modifications in the furan hepatotoxicity and carcinogenicity.
Breast cancer is a global public health problem and the most frequent cause of cancer death among women. Mammary carcinogenesis is driven not only by genetic alterations but also by epigenetic ...disturbances. Because epigenetic marks are potentially reversible they represent promising molecular targets for breast cancer prevention interventions. Selenium is a promising anti-breast cancer trace element that has shown the modulation of DNA methylation and histone post-translational modifications in other malignancies. This study aimed to evaluate the effects of selenium compounds methylseleninic acid (MSA) and selenite on cell proliferation and death, expression of the tumor suppressor gene RASSF1A and epigenetic marks in MCF-7 human breast adenocarcinoma cells. Treatment with MSA or selenite markedly inhibited (P<0.05) in a dose-dependent manner the proliferation of MCF-7 cells. MSA induced (P<0.05) G2/M cell arrest while selenite presented the opposite effect. Regarding cell death induction, MSA acted mainly by inducing apoptosis (P<0.05), while selenite only induced necrosis (P<0.05). Furthermore selenite, but not MSA, markedly induced (P<0.05) cytotoxicity and increased (P<0.05) RASSF1A expression. Both selenium compounds inhibited (P<0.05) DNMT1 expression. MSA decreased (P<0.05) H3K9me3 and increased (P<0.05) H4K16ac, while selenite decreased (P<0.05) this latter histone mark. To the best of our knowledge this is the first report showing that selenite and MSA modulate epigenetic marks specifically in breast cancer cells. Our data reinforce the anti-breast cancer potential of selenium that is dependent on its chemical form. Furthermore the data show that epigenetic mechanisms represent relevant molecular targets involved in selenium inhibitory effects in breast cancer cells.
Furan is a significant food contaminant and a potent hepatotoxicant and rodent liver carcinogen. The carcinogenic effect of furan has been attributed to genotoxic and non-genotoxic, including ...epigenetic, changes in the liver; however, the mechanisms of the furan-induced liver tumorigenicity are still unclear. The goal of the present study was to investigate the role of transcriptomic and epigenetic events in the development of hepatic lesions in Fischer (F344) rats induced by furan treatment in a classic 2-year rodent tumorigenicity bioassay. High-throughput whole-genome transcriptomic analysis demonstrated distinct alterations in gene expression in liver lesions induced in male F344 rats treated with 0.92 or 2.0 mg furan/kg body weight (bw)/day for 104 weeks. Compared to normal liver tissue, 1336 and 1541 genes were found to be differentially expressed in liver lesions in rats treated with 0.92 and 2.0 mg furan/kg bw/day, respectively, among which 1001 transcripts were differentially expressed at both doses. Pairing transcriptomic and next-generation bisulfite sequencing analyses of the common differentially expressed genes identified 42 CpG island-containing genes in which the methylation level was correlated inversely with gene expression. Forty-eight percent of these genes (20 genes, including
Areg
,
Jag1
, and
Foxe1
) that exhibited the most significant methylation and gene expression changes were involved in key pathways associated with different aspects of liver pathology. Our findings illustrate that gene-specific DNA methylation changes have functional consequences and may be an important component of furan hepatotoxicity and hepatocarcinogenicity.
Acrylamide has been classified as a “Group 2A carcinogen” (probably carcinogenic to humans) by the International Agency for Research on Cancer. The carcinogenicity of acrylamide is attributed to its ...well-recognized genotoxicity. In the present study, we investigated the effect of acrylamide on epigenetic alterations in mice. Female B6C3F1 mice received acrylamide in drinking water for 28 days, at doses previously used in a 2 year cancer bioassay (0, 0.0875, 0.175, 0.35, and 0.70 mM), and the genotoxic and epigenetic effects were investigated in lungs, a target organ for acrylamide carcinogenicity, and livers, a nontarget organ. Acrylamide exposure resulted in a dose-dependent formation of N7-(2-carbamoyl-2-hydroxyethyl)guanine and N3-(2-carbamoyl-2-hydroxyethyl)adenine in liver and lung DNA. In contrast, the profiles of global epigenetic alterations differed between the two tissues. In the lungs, acrylamide exposure resulted in a decrease of histone H4 lysine 20 trimethylation (H4K20me3), a common epigenetic feature of human cancer, while in the livers, there was increased acetylation of histone H3 lysine 27 (H3K27ac), a gene transcription activating mark. Treatment with 0.70 mM acrylamide also resulted in substantial alterations in the DNA methylation and whole transcriptome in the lungs and livers; however, there were substantial differences in the trends of DNA methylation and gene expression changes between the two tissues. Analysis of differentially expressed genes showed a marked up-regulation of genes and activation of the gene transcription regulation pathway in livers, but not lungs. This corresponded to increased histone H3K27ac and DNA hypomethylation in livers, in contrast to hypermethylation and transcription silencing in lungs. Our results demonstrate that acrylamide induced global epigenetic alterations independent of its genotoxic effects, suggesting that epigenetic events may determine the organ-specific carcinogenicity of acrylamide. Additionally this study provides strong support for the importance of epigenetic alterations, in addition to genotoxic events, in the mechanism of carcinogenesis induced by genotoxic chemical carcinogens.
Nonalcoholic fatty liver disease (NAFLD) is a major health problem and a leading cause of chronic liver disease in the United States and developed countries. In humans, genetic factors greatly ...influence individual susceptibility to NAFLD. The goals of this study were to compare the magnitude of interindividual differences in the severity of liver injury induced by methyl‐donor deficiency among individual inbred strains of mice and to investigate the underlying mechanisms associated with the variability. Feeding mice a choline‐ and folate‐deficient diet for 12 wk caused liver injury similar to NAFLD. The magnitude of liver injury varied among the strains, with the order of sensitivity being A/J ≈ C57BL/6J ≈ C3H/HeJ < 129S1/SvImJ ≈ CAST/EiJ < PWK/PhJ < WSB/EiJ. The interstrain variability in severity of NAFLD liver damage was associated with dysregulation of genes involved in lipid metabolism, primarily with a down‐regulation of the peroxisome proliferator receptor α (PPARα)‐regulated lipid catabolic pathway genes. Markers of oxidative stress and oxidative stress‐induced DNA damage were also elevated in the livers but were not correlated with severity of liver damage. These findings suggest that the PPARα‐regulated metabolism network is one of the key mechanisms determining interstrain susceptibility and severity of NAFLD in mice.—Tryndyak, V., de Conti, A., Kobets, T., Kutanzi, K., Koturbash, I., Han, T., Fuscoe, J. C., Latendresse, J. R., Melnyk, S., Shymonyak, S., Collins, L., Ross, S. A., Rusyn, I., Beland, F. A., Pogribny, I. P. Interstrain differences in the severity of liver injury induced by a choline‐ and folate‐deficient diet in mice are associated with dysregulation of genes involved in lipid metabolism. FASEB J. 26, 4592–4602 (2012). www.fasebj.org
Abstract
Nonalcoholic fatty liver disease (NAFLD) is becoming a major etiological risk factor for hepatocellular carcinoma (HCC) in the United States and other Western countries. In this study, we ...investigated the role of gene-specific promoter cytosine DNA methylation and gene expression alterations in the development of NAFLD-associated HCC in mice using (1) a diet-induced animal model of NAFLD, (2) a Stelic Animal Model of nonalcoholic steatohepatitis-derived HCC, and (3) a choline- and folate-deficient (CFD) diet (CFD model). We found that the development of NAFLD and its progression to HCC was characterized by down-regulation of glycine N-methyltransferase (Gnmt) and this was mediated by progressive Gnmt promoter cytosine DNA hypermethylation. Using a panel of genetically diverse inbred mice, we observed that Gnmt down-regulation was an early event in the pathogenesis of NAFLD and correlated with the extent of the NAFLD-like liver injury. Reduced GNMT expression was also found in human HCC tissue and liver cancer cell lines. In in vitro experiments, we demonstrated that one of the consequences of GNMT inhibition was an increase in genome methylation facilitated by an elevated level of S-adenosyl-L-methionine. Overall, our findings suggest that reduced Gnmt expression caused by promoter hypermethylation is one of the key molecular events in the development of NAFLD-derived HCC and that assessing Gnmt methylation level may be useful for disease stratification.
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