Hypermethylation-repressed methionine adenosyltransferase 1A as a potential biomarker for hepatocellular carcinoma

MAT1A Suppression by the CTBP1/HDAC1/HDAC2 Transcriptional Complex Induces Immune Escape and Reduces Ferroptosis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) remains a significant health burden globally due to its high prevalence and morbidity. C-terminal-binding protein 1 (CTBP1) is a transcriptional corepressor that modulates gene transcription by interacting with transcription factors or chromatin-modifying enzymes. High CTBP1 expression has been associated with the progression of various human cancers. In this study, bioinformatics analysis suggested the existence of a CTBP1/histone deacetylase 1 (HDAC1)/HDAC2 transcriptional complex that regulates the expression of methionine adenosyltransferase 1A (MAT1A), whose loss has been associated with ferroptosis suppression and HCC development. Thus, this study aims to investigate the interactions between the CTBP1/HDAC1/HDAC2 complex and MAT1A and their roles in HCC progression. First, high expression of CTBP1 was observed in HCC tissues and cells, where it promoted HCC cell proliferation and mobility while inhibiting cell apoptosis. CTBP1 interacted with HDAC1 and HDAC2 to suppress the MAT1A transcription, and silencing of either HDAC1 or HDAC2 or overexpression of MAT1A led to the inhibition of cancer cell malignancy. In addition, MAT1A overexpression resulted in increased S-adenosylmethionine levels, which promoted ferroptosis of HCC cells directly or indirectly by increasing CD8+ T-cell cytotoxicity and interferon-γ production. In vivo, MAT1A overexpression suppressed growth of CTBP1-induced xenograft tumors in mice while enhancing immune activity and inducing ferroptosis. However, treatment with ferrostatin-1, a ferroptosis inhibitor, blocked the tumor-suppressive effects of MAT1A. Collectively, this study reveals that the CTBP1/HDAC1/HDAC2 complex-induced MAT1A suppression is liked to immune escape and reduced ferroptosis of HCC cells.

NFATc1 is a tumor suppressor in hepatocellular carcinoma and induces tumor cell apoptosis by activating the FasL-mediated extrinsic signaling pathway

Nuclear factor of activated T cells (NFAT) is a family of transcription factors that have important functions in many tumors. However, the expression level and functional role of NFAT in hepatocellular carcinoma (HCC) remain unclear. In this study, we showed that NFATc1 expression was decreased in both HCC tissues and cell lines. Low expression of NFATc1 was correlated with larger tumor size, advanced tumor‐node‐metastasis (TNM) stage, high serum AFP level, and liver cirrhosis. Furthermore, patients with low NFATc1 expression exhibited poor prognosis. Ectopic expression of NFATc1 in HCC cells inhibited proliferation and colony formation, leading to G1 arrest and induction of apoptosis. In addition, we demonstrated that NFATc1 increased Fas ligand (FasL) expression by directly binding to its promoter and activated the extrinsic apoptotic pathway. NFATc1 and FasL expression patterns and their prognostic value for patients with HCC were also evaluated in TCGA Liver Hepatocellular Carcinoma database. Knock‐down of FasL expression by siRNA in HCC cell lines abolished NFATc1's antiproliferative and pro‐apoptotic effects. In conclusion, NFATc1 is frequently inactivated in HCC and functions as a tumor suppressor in liver carcinogenesis. Ectopic expression of NFATc1 in HCC cells induces apoptosis by activating the FasL‐mediated extrinsic signaling pathway.

Arid1a Has Context-Dependent Oncogenic and Tumor Suppressor Functions in Liver Cancer

ARID1A, an SWI/SNF chromatin-remodeling gene, is commonly mutated in cancer and hypothesized to be tumor suppressive. In some hepatocellular carcinoma patients, ARID1A was highly expressed in primary tumors but not in metastatic lesions, suggesting that ARID1A can be lost after initiation. Mice with liver-specific homozygous or heterozygous Arid1a loss were resistant to tumor initiation while ARID1A overexpression accelerated initiation. In contrast, homozygous or heterozygous Arid1a loss in established tumors accelerated progression and metastasis. Mechanistically, gain of Arid1a function promoted initiation by increasing CYP450-mediated oxidative stress, while loss of Arid1a within tumors decreased chromatin accessibility and reduced transcription of genes associated with migration, invasion, and metastasis. In summary, ARID1A has context-dependent tumor-suppressive and oncogenic roles in cancer.

5-Aza-2<-deoxycytidine induces hepatoma cell apoptosis via enhancing methionine adenosyltransferase 1A expression and inducing S-adenosylmethionine production

In hepatocellular cancer (HCC), lack of response to chemotherapy and radiation treatment can be caused by a loss of epigenetic modifications of cancer cells. Methionine adenosyltransferase 1A is inactivated in HCC and may be stimulated by an epigenetic change involving promoter hypermethylation. Therefore, drugs releasing epigenetic repression have been proposed to reverse this process. We studied the effect of the demethylating reagent 5-aza-2<-deoxycitidine (5-Aza-CdR) on MAT1A gene expression, DNA methylation and S-adenosylmethionine (SAMe) production in the HCC cell line Huh7. We found that MAT1A mRNA and protein expression were activated in Huh7 cells with the treatment of 5-Aza-CdR; the status of promoter hypermethylation was reversed. At the same time, MAT2A mRNA and protein expression was significantly reduced in Huh7 cells treated with 5-Aza-CdR, while SAMe production was significantly induced. However, 5-Aza-CdR showed no effects on MAT2A methylation. Furthermore, 5-Aza-CdR inhibited the growth of Huh7 cells and induced apoptosis and through down-regulation of Bcl-2, up-regulation of Bax and caspase-3. Our observations suggest that 5-Aza- CdR exerts its anti-tumor effects in Huh7 cells through an epigenetic change involving increased expression of the methionine adenosyltransferase 1A gene and induction of S-adenosylmethionine production.

DNA methylation, microRNAs, and their crosstalk as potential biomarkers in hepatocellular carcinoma

Epigenetic alterations have been identified as a major characteristic in human cancers. Advances in the field of epigenetics have contributed significantly in refining our knowledge of molecular mechanisms underlying malignant transformation. DNA methylation and microRNA expression are epigenetic mechanisms that are widely altered in human cancers including hepatocellular carcinoma (HCC), the third leading cause of cancer related mortality worldwide. Both DNA methylation and microRNA expression patterns are regulated in developmental stage specific-, cell type specific- and tissue-specific manner. The aberrations are inferred in the maintenance of cancer stem cells and in clonal cell evolution during carcinogenesis. The availability of genome-wide technologies for DNA methylation and microRNA profiling has revolutionized the field of epigenetics and led to the discovery of a number of epigenetically silenced microRNAs in cancerous cells and primary tissues. Dysregulation of these microRNAs affects several key signalling pathways in hepatocarcinogenesis suggesting that modulation of DNA methylation and/or microRNA expression can serve as new therapeutic targets for HCC. Accumulative evidence shows that aberrant DNA methylation of certain microRNA genes is an event specifically found in HCC which correlates with unfavorable outcomes. Therefore, it can potentially serve as a biomarker for detection as well as for prognosis, monitoring and predicting therapeutic responses in HCC.

Alterations of epigenetics and microRNA in hepatocellular carcinoma

Studies have shown that alterations of epigenetics and microRNA (miRNA) play critical roles in the initiation and progression of hepatocellular carcinoma (HCC). Epigenetic silencing of tumor suppressor genes in HCC is generally mediated by DNA hypermethylation of CpG island promoters and histone modifications such as histone deacetylation, methylation of histone H3 lysine 9 (H3K9) and tri-methylation of H3K27. Chromatin-modifying drugs such as DNA methylation inhibitors and histone deacetylase inhibitors have shown clinical promise for cancer therapy. miRNA are small non-coding RNA that regulate expression of various target genes. Specific miRNA are aberrantly expressed and play roles as tumor suppressors or oncogenes during hepatocarcinogenesis. We and other groups have demonstrated that important tumor suppressor miRNA are silenced by epigenetic alterations, resulting in activation of target oncogenes in human malignancies including HCC. Restoring the expression of tumor suppressor miRNA by inhibitors of DNA methylation and histone deacetylase may be a promising therapeutic strategy for HCC.

Choline's role in maintaining liver function: new evidence for epigenetic mechanisms

PURPOSE OF REVIEW

Humans eating diets low in choline develop fatty liver and liver damage. Rodents fed choline-methionine-deficient diets not only develop fatty liver, but also progress to develop fibrosis and hepatocarcinoma. This review focuses on the role of choline in liver function, with special emphasis on the epigenetic mechanisms of action.

RECENT FINDINGS

Dietary intake of methyl donors like choline influences the methylation of DNA and histones, thereby altering the epigenetic regulation of gene expression. The liver is the major organ within which methylation reactions occur, and many of the hepatic genes involved in pathways for the development of fatty liver, hepatic fibrosis, and hepatocarcinomas are epigenetically regulated.

SUMMARY

Dietary intake of choline varies over a three-fold range and many humans have genetic polymorphisms that increase their demand for choline. Choline is an important methyl donor needed for the generation of S-adenosylmethionine. Dietary choline intake is an important modifier of epigenetic marks on DNA and histones, and thereby modulates the gene expression in many of the pathways involved in liver function and dysfunction.