Histone modification-mediated CYP2E1 gene expression and apoptosis of HepG2 cells

Epigenetic Activation of Cytochrome P450 1A2 Sensitizes Hepatocellular Carcinoma Cells to Sorafenib

Cytochrome P450 1A2 (CYP1A2) is a known tumor suppressor in hepatocellular carcinoma (HCC), but its expression is repressed in HCC and the underlying mechanism is unclear. In this study, we investigated the epigenetic mechanisms of CYP1A2 repression and potential therapeutic implications. In HCC tumor tissues, the methylation rates of CYP1A2 CpG island (CGI) and DNA methyltransferase (DNMT) 3A protein levels were significantly higher, and there was a clear negative correlation between DNMT3A and CYP1A2 protein expression. Knockdown of DNMT3A by siRNA significantly increased CYP1A2 expression in HCC cells. Additionally, treating HCC cells with decitabine (DAC) resulted in a dose-dependent upregulation of CYP1A2 expression by reducing the methylation level of CYP1A2 CGI. Furthermore, we observed a decreased enrichment of H3K27Ac in the promoter region of CYP1A2 in HCC tissues. Treatment with the trichostatin A (TSA) restored CYP1A2 expression in HCC cells by increasing H3K27Ac levels in the CYP1A2 promoter region. Importantly, combination treatment of sorafenib with DAC or TSA resulted in a leftward shift of the dose-response curve, lower IC50 values, and reduced colony numbers in HCC cells. Our findings suggest that hypermethylation of the CGI at the promoter, mediated by the high expression of DNMT3A, and hypoacetylation of H3K27 in the CYP1A2 promoter region, leads to CYP1A2 repression in HCC. Epigenetic drugs DAC and TSA increase HCC cell sensitivity to sorafenib by restoring CYP1A2 expression. Our study provides new insights into the epigenetic regulation of CYP1A2 in HCC and highlights the potential of epigenetic drugs as a therapeutic approach for HCC. SIGNIFICANCE STATEMENT: This study marks the first exploration of the epigenetic mechanisms underlying cytochrome P450 (CYP) 1A2 suppression in hepatocellular carcinoma (HCC). Our findings reveal that heightened DNA methyltransferase expression induces hypermethylation of the CpG island at the promoter, coupled with diminished H3K27Ac levels, resulting in the repression of CYP1A2 in HCC. The use of epigenetic drugs such as decitabine and trichostatin A emerges as a novel therapeutic avenue, demonstrating their potential to restore CYP1A2 expression and enhance sorafenib sensitivity in HCC cells.

CYP2E1 plays a suppressive role in hepatocellular carcinoma by regulating Wnt/Dvl2/β-catenin signaling

Objective

Knowledge of the role of CYP2E1 in hepatocarcinogenesis is largely based on epidemiological and animal studies, with a primary focus on the role of CYP2E1 in metabolic activation of procarcinogens. Few studies have directly assessed the effects of CYP2E1 on HCC malignant phenotypes.

Methods

The expression of CYP2E1 in HCC tissues was determined by qRT-PCR, western blotting and immunohistochemistry. Overexpression of CYP2E1 in HCC cell was achieved by lentivirus transfection. The function of CYP2E1 were detected by CCK-8, wound healing, transwell assays, xenograft models and pulmonary metastasis model. TOP/FOPFlash reporter assay, western blotting, functional rescue experiments, Co-immunoprecipitation and reactive oxygen species detection were conducted to reveal the underlying mechanism of the tumor suppressive role of CYP2E1.

Results

CYP2E1 expression is down-regulated in HCC tissues, and this downregulation was associated with large tumor diameter, vascular invasion, poor differentiation, and shortened patient survival time. Ectopic expression of CYP2E1 inhibits the proliferation, invasion and migration and epithelial-to-mesenchymal transition of HCC cells in vitro, and inhibits tumor formation and lung metastasis in nude mice. Mechanistic investigations show that CYP2E1 overexpression significantly inhibited Wnt/β-catenin signaling activity and decreased Dvl2 expression in HCC cells. An increase in Dvl2 expression restored the malignant phenotype of HCC cells. Notably, CYP2E1 promoted the ubiquitin-mediated degradation of Dvl2 by strengthening the interaction between Dvl2 and the E3 ubiquitin ligase KLHL12 in CYP2E1-stable HCC cells. CYP2E1-induced ROS accumulation was a critical upstream event in the Wnt/β-Catenin pathway in CYP2E1-overexpressing HCC cells.

Conclusions

These results provide novel insight into the role of CYP2E1 in HCC and the tumor suppressor role of CYP2E1 can be attributed to its ability to manipulate Wnt/Dvl2/β-catenin pathway via inducing ROS accumulation, which provides a potential target for the prevention and treatment of HCC.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03396-6.

Molecular effects and retinopathy induced by hydroxychloroquine during SARS-CoV-2 therapy: Role of CYP450 isoforms and epigenetic modulations

Antimalaria drugs such as chloroquine (CQ) and hydroxychloroquine (HCQ) have been administered to several inflammatory diseases including rheumatoid arthritis and systemic lupus erythematosus, and infectious diseases such as acquired immune deficiency syndrome and influenza. Recently, several patients infected with novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) were given HCQ, and showed a discrepant response. HCQ inhibits SARS-CoV-2 cell entry, and inflammatory cascade by interfering with lysosomal and endosomal activities, and autophagy, impeding virus-membrane fusion, and inhibiting cytokine production resulted from inflammatory pathways activation. Despite ongoing administration of HCQ in a wide spectrum of disorders, there are some reports about several side effects, especially retinopathy in some patients treated with HCQ. Cytochrome P450 (CYP450) and its isoforms are the main metabolizers of HCQ and CQ. Pharmacokinetic properties of CYP enzymes are influenced by CYP polymorphism, non-coding RNAs, and epigenetic mechanisms such as DNA methylation, and histone acetylation. Accumulating evidence about side effects of HCQ in some patients raise the possibility that different response of patients to HCQ might be due to difference in their genome. Therefore, CYP450 genotyping especially for CYP2D6 might be helpful to refine HCQ dosage. Also, regular control of retina should be considered for patients under HCQ treatment. The major focus of the present review is to discuss about the pharmacokinetic and pharmacodynamic properties of CQ and HCQ that may be influenced by epigenetic mechanisms, and consequently cause several side effects especially retinopathy during SARS-CoV-2 therapy.

Histone Deacetylase Expressions in Hepatocellular Carcinoma and Functional Effects of Histone Deacetylase Inhibitors on Liver Cancer Cells In Vitro

Hepatocellular carcinoma (HCC) is a leading cause for deaths worldwide. Histone deacetylase (HDAC) inhibition (HDACi) is emerging as a promising therapeutic strategy. However, most pharmacological HDACi unselectively block different HDAC classes and their molecular mechanisms of action are only incompletely understood. The aim of this study was to systematically analyze expressions of different HDAC classes in HCC cells and tissues and to functionally analyze the effect of the HDACi suberanilohydroxamic acid (SAHA) and trichostatin A (TSA) on the tumorigenicity of HCC cells. The gene expression of all HDAC classes was significantly increased in human HCC cell lines (Hep3B, HepG2, PLC, HuH7) compared to primary human hepatocytes (PHH). The analysis of HCC patient data showed the increased expression of several HDACs in HCC tissues compared to non-tumorous liver. However, there was no unified picture of regulation in three different HCC patient datasets and we observed a strong variation in the gene expression of different HDACs in tumorous as well as non-tumorous liver. Still, there was a strong correlation in the expression of HDAC class IIa (HDAC4, 5, 7, 9) as well as HDAC2 and 8 (class I) and HDAC10 (class IIb) and HDAC11 (class IV) in HCC tissues of individual patients. This might indicate a common mechanism of the regulation of these HDACs in HCC. The Cancer Genome Atlas (TCGA) dataset analysis revealed that HDAC4, HDAC7 and HDAC9 as well as HDAC class I members HDAC1 and HDAC2 is significantly correlated with patient survival. Furthermore, we observed that SAHA and TSA reduced the proliferation, clonogenicity and migratory potential of HCC cells. SAHA but not TSA induced features of senescence in HCC cells. Additionally, HDACi enhanced the efficacy of sorafenib in killing sorafenib-susceptible cells. Moreover, HDACi reestablished sorafenib sensitivity in resistant HCC cells. In summary, HDACs are significantly but differently increased in HCC, which may be exploited to develop more targeted therapeutic approaches. HDACi affect different facets of the tumorigenicity of HCC cells and appears to be a promising therapeutic approach alone or in combination with sorafenib.

Epigenetic regulation of histone H3 in the process of hepatocellular tumorigenesis

Better understanding of epigenetic regulation of hepatocellular carcinoma (HCC) will help us to cure this most common malignant liver cancer worldwide. The underlying mechanisms of HCC tumorigenesis are genomic aberrations regulated by genetic and epigenetic modifications. Histone H3 lysine modifications regulate histone structure and modulate transcriptional factor binding with target gene promoters. Targetting genes include VASH2, fatty acids synthase, RIZ1, FBP1, MPP1/3, YAP, which affect tumorigenesis, metabolisms, angiogenesis, and metastasis. Signal pathway studies demonstrate that the HGF-MET-MLL axis, phosphatase and tensin homolog (PTEN)-PI3K-Akt axis; WNT-β-catenin signal pathway is involved in histone H3 modification. A variety of factors such as virus infection, reactive oxygen species, food-borne toxins, irradiation, or non-coding RNA cause hepatocellular DNA damage or modification. Dysfunctional DNA repair mechanisms, including those at the epigenetic level are also major causes of HCC tumorigenesis. The development of therapies based on epigenetic regulatory mechanisms has great potential to advance the care of HCC patients in the future.

The characteristics of the ancient cell death suppressor, TMBIM6, and its related signaling pathways after endoplasmic reticulum stress

Activation of the unfolded protein response in combination with generation of reactive oxygen species, from cytochrome P450 members and NADPH-P450 reductases, are two major consequences of Endoplasmic Reticulum (ER) stress that cause oxidative damage and cell death. Herein, we reviewed the role of Bax Inhibitor-1 (BI-1), an evolutionarily conserved protein encoded by the Transmembrane Bax inhibitor Motif Containing 6 gene, in protection from ER stress. As BI-1 has multimodal properties that can target a wide array of pathophysiological consequences after injury, our main objective was to explore BI-1's protective role in ER stress and its potential signaling pathways.

Regulation of cytochrome P450 expression by microRNAs and long noncoding RNAs: Epigenetic mechanisms in environmental toxicology and carcinogenesis

Environmental exposures to hazardous chemicals are associated with a variety of human diseases and disorders, including cancers. Phase I metabolic activation and detoxification reactions catalyzed by cytochrome P450 enzymes (CYPs) affect the toxicities of many xenobiotic compounds. Proper regulation of CYP expression influences their biological effects. Noncoding RNAs (ncRNAs) are involved in regulating CYP expression, and ncRNA expression is regulated in response to environmental chemicals. The mechanistic interactions between ncRNAs and CYPs associated with the toxicity and carcinogenicity of environmental chemicals are described in this review, focusing on microRNA-dependent CYP regulation. The role of long noncoding RNAs in regulating CYP expression is also presented and new avenues of research concerning this regulatory mechanism are described.

Alcohol-Induced Epigenetic Changes in Cancer

Chronic, heavy alcohol consumption is associated with serious negative health effects, including the development of several cancer types. One of the pathways affected by alcohol toxicity is the one-carbon metabolism. The alcohol-induced impairment of this metabolic pathway results in epigenetic changes associated with cancer development. These epigenetic changes are induced by folate deficiency and by products of the ethanol metabolism. The changes induced by long-term heavy ethanol consumption result in elevations of homocysteine and S-adenosyl-homocysteine (SAH) and reductions in S-adenosylmethionine (SAM) and antioxidant glutathione (GSH) levels, leading to abnormal promoter gene hypermethylation, global hypomethylation, and metabolic insufficiency of antioxidant defense mechanisms. In addition, reactive oxygen species (ROS) generated during the ethanol metabolism induce alterations in DNA methylation patterns that play a critical role in cancer development. Specific epigenetic changes in esophageal, hepatic, and colorectal cancers have been detected in blood samples and proposed to be used clinically as epigenetic biomarkers for diagnosis and prognosis of these cancers. Also, genetic variants of genes involved in one-carbon metabolism and ethanol metabolism were found to modulate the relationship between alcohol-induced epigenetic changes and cancer risk. Furthermore, alcohol metabolism products have been associated with an increase in NADH levels, which lead to histone modifications and changes in gene expression that in turn influence cancer susceptibility. Chronic excessive use of alcohol also affects selected members of the family of microRNAs, and as miRNAs could act as epigenetic regulators, this may play an important role in carcinogenesis. In conclusion, targeting alcohol-induced epigenetic changes in several cancer types could make available clinical tools for the diagnosis, prognosis, and treatment of these cancers, with an important role in precision medicine.

LncRNA-uc002mbe.2 Interacting with hnRNPA2B1 Mediates AKT Deactivation and p21 Up-Regulation Induced by Trichostatin in Liver Cancer Cells

Long non-coding RNAs (lncRNAs) have been implicated in liver carcinogenesis. We previously showed that the induction of lncRNA-uc002mbe.2 is positively associated with the apoptotic effect of trichostatin A (TSA) in hepatocellular carcinoma (HCC) cells. The current study further analyzed the role of uc002mbe.2 in TSA-induced liver cancer cell death. The level of uc002mbe.2 was markedly increased by TSA in the cytoplasm of HCC cells. Knockdown of uc002mbe.2 prohibited TSA-induced G2/M cell cycle arrest, p21 induction, and apoptosis of Huh7 cells and reversed the TSA-mediated decrease in p-AKT. RNA pull-down and RNA-binding protein immunoprecipitation (RIP) assays revealed that TSA induced an interaction between uc002mbe.2 and heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1) in Huh7 cells. This interaction mediated AKT deactivation and p21 induction in liver cancer cells. In an athymic xenograft mouse model, knockdown of uc002mbe.2 significantly prohibited the TSA-mediated reduction in tumor size and weight. In addition, the ability of TSA to reduce hnRNPA2B1 and p-AKT levels and induce p21 in the xenograft tumors was prevented by uc002mbe.2 knockdown. Therefore, the interaction of uc002mbe.2 and hnRNPA2B1 in mediating AKT deactivation and p21 induction is involved in the cytostatic effect of trichostatin in liver cancer cells.

Alterations of Histone Modifications Contribute to Pregnane X Receptor-Mediated Induction of CYP3A4 by Rifampicin

CYP3A4 is one of the major drug-metabolizing enzymes in human and is responsible for the metabolism of 60% of clinically used drugs. Many drugs are able to induce the expression of CYP3A4, which usually causes drug-drug interactions and adverse drug reactions. This study aims to explore the role of histone modifications in rifampicin-induced expression of CYP3A4 in LS174T cells. We found that the induction of CYP3A4 mRNA (4- to 15-fold) by rifampicin in LS174T cells was associated with increased levels of histone H3 lysine 4 trimethylation (H3K4me3, above 1.8-fold) and H3 acetylation (above 2-fold) and a decreased level of histone H3 lysine 27 trimethylation (H3K27me3, about 50%) in the CYP3A4 promoter. Rifampicin enhanced recruitment to the CYP3A4 promoter of nuclear receptor coactivator 6 (NCOA6, above 3-fold) and histone acetyltransferase p300 (p300, above 1.6-fold). Silencing NCOA6 or p300 by short-hairpin RNAs resulted in inhibition of the CYP3A4 induction as well as altered levels of H3K4me3, H3K27me3, or H3 acetylation in the CYP3A4 promoter. Knockdown of pregnane X receptor (PXR) expression not only suppressed the recruitment of NCOA6 and p300 but also abolished the changes caused by rifampicin in H3K4me3, H3K27me3, and H3 acetylation levels in the CYP3A4 promoter. Moreover, rifampicin treatment enhanced the nuclear accumulation and interactions between PXR and NCOA6/p300. In conclusion, we show that the alterations of histone modifications contribute to the PXR-mediated induction of CYP3A4 by rifampicin.

New Insights into the Epigenetics of Hepatocellular Carcinoma

Hepatocellular Carcinoma (HCC) is one of the most predominant malignancies with high fatality rate. This deadly cancer is rising at an alarming rate because it is quite resistant to radio- and chemotherapy. Different epigenetic mechanisms such as histone modifications, DNA methylation, chromatin remodeling, and expression of noncoding RNAs drive the cell proliferation, invasion, metastasis, initiation, progression, and development of HCC. These epigenetic alterations because of potential reversibility open way towards the development of biomarkers and therapeutics. The contribution of these epigenetic changes to HCC development has not been thoroughly explored yet. Further research on HCC epigenetics is necessary to better understand novel molecular-targeted HCC treatment and prevention. This review highlights latest research progress and current updates regarding epigenetics of HCC, biomarker discovery, and future preventive and therapeutic strategies to combat the increasing risk of HCC.

Integrated Multiple "-omics" Data Reveal Subtypes of Hepatocellular Carcinoma

Hepatocellular carcinoma is one of the most heterogeneous cancers, as reflected by its multiple grades and difficulty to subtype. In this study, we integrated copy number variation, DNA methylation, mRNA, and miRNA data with the developed “cluster of cluster” method and classified 256 HCC samples from TCGA (The Cancer Genome Atlas) into five major subgroups (S1-S5). We observed that this classification was associated with specific mutations and protein expression, and we detected that each subgroup had distinct molecular signatures. The subclasses were associated not only with survival but also with clinical observations. S1 was characterized by bulk amplification on 8q24, TP53 mutation, low lipid metabolism, highly expressed onco-proteins, attenuated tumor suppressor proteins and a worse survival rate. S2 and S3 were characterized by telomere hypomethylation and a low expression of TERT and DNMT1/3B. Compared to S2, S3 was associated with less copy number variation and some good prognosis biomarkers, including CRP and CYP2E1. In contrast, the mutation rate of CTNNB1 was higher in S3. S4 was associated with bulk amplification and various molecular characteristics at different biological levels. In summary, we classified the HCC samples into five subgroups using multiple “-omics” data. Each subgroup had a distinct survival rate and molecular signature, which may provide information about the pathogenesis of subtypes in HCC.

The antitumor effect of TIG3 in liver cancer cells is involved in ERK1/2 inhibition

Tazarotene-induced gene 3 (TIG3) was first characterized in tazarotene-treated human keratinocytes and identified as a retinoic acid responder gene, an important mediator of antitumor effects by retinoids. In this study, we aim to investigate the inhibitory effect of TIG3 on the growth of liver cancer and explore its underlying mechanism. Human hepatocellular carcinoma (HCC) Hep3B cells were transfected with plasmid GV141 carrying full-length TIG3 complementary DNA (cDNA). The effects of TIG3 on cell proliferation, apoptosis, and migration were determined in vitro. The suppressor effect of TIG3 on tumor growth was evaluated in vivo in a nude mouse HCC model. We observed that TIG3 expression is decreased in the Hep3B cell line as well as primary HCC tumors, and TIG3 expression inversely correlates with Ki-67 expression. Overexpression of TIG3 suppresses tumor growth in HCC both in vitro and in vivo via ERK1/2 inhibition by promoting apoptosis and inhibiting proliferation and migration. These findings identify TIG3 as an attractive therapeutic target for HCC.

Epigenetic modification of histone 3 lysine 27: mediator subunit MED25 is required for the dissociation of polycomb repressive complex 2 from the promoter of cytochrome P450 2C9

The Mediator complex is vital for the transcriptional regulation of eukaryotic genes. Mediator binds to nuclear receptors at target response elements and recruits chromatin-modifying enzymes and RNA polymerase II. Here, we examine the involvement of Mediator subunit MED25 in the epigenetic regulation of human cytochrome P450 2C9 (CYP2C9). MED25 is recruited to the CYP2C9 promoter through association with liver-enriched HNF4α, and we show that MED25 influences the H3K27 status of the HNF4α binding region. This region was enriched for the activating marker H3K27ac and histone acetyltransferase CREBBP after MED25 overexpression but was trimethylated when MED25 expression was silenced. The epigenetic regulator Polycomb repressive complex (PRC2), which represses expression by methylating H3K27, plays an important role in target gene regulation. Silencing MED25 correlated with increased association of PRC2 not only with the promoter region chromatin but with HNF4α itself. We confirmed the involvement of MED25 for fully functional preinitiation complex recruitment and transcriptional output in vitro. Formaldehyde-assisted isolation of regulatory elements (FAIRE) revealed chromatin conformation changes that were reliant on MED25, indicating that MED25 induced a permissive chromatin state that reflected increases in CYP2C9 mRNA. For the first time, we showed evidence that a functionally relevant human gene is transcriptionally regulated by HNF4α via MED25 and PRC2. CYP2C9 is important for the metabolism of many exogenous chemicals including pharmaceutical drugs as well as endogenous substrates. Thus, MED25 is important for regulating the epigenetic landscape resulting in transcriptional activation of a highly inducible gene, CYP2C9.

Epigenetic histone modifications in a clinically relevant rat model of chronic ethanol-binge-mediated liver injury

PURPOSE

Ethanol binge augments liver injury after chronic ethanol consumption in humans, but the mechanism behind the enhanced liver injury by ethanol binge is not known. In this study we used a clinically relevant rat model in which liver injury is amplified by binge after chronic ethanol treatment and investigated the importance of histone modifications.

METHODS

Eight-week-old Sprague-Dawley rats were fed ethanol in a liquid diet for 4 weeks. Control rats were fed an isocaloric liquid diet. This was followed by three binge administrations of ethanol (intragastric 5 g/kg body weight, 12 h apart). In the control, ethanol was replaced by water. Four hours after the last binge administration, liver samples were analyzed for histone modifications and parameters of liver injury.

RESULTS

Chronic ethanol administration alone caused an increase in histone H3 ser10 and ser28 (H3S10 or S28) phosphorylation, and binge ethanol reduced their levels. Levels of dually modified phosphoacetylated histone H3 (H3AcK9/PS10) increased after acute binge ethanol and remained same after chronic ethanol binge. In contrast, histone H3 lysine-9 acetylation (H3AcK9) was not increased after chronic ethanol but increased significantly after acute binge and chronic ethanol binge. Increase in histone acetylation was accompanied by increased phospho-ERK1/2 in the nuclear extracts. Increased acetylation after chronic ethanol binge was also accompanied by increased protein levels of GCN5 histone acetyl transferase and a modest increase in HDAC3 in the nucleus. Histone lysine-9 dimethylation was significantly increased after chronic ethanol binge. Chronic ethanol binge also resulted in a decrease in the SAM:SAH ratio with a relative decrease of SAM levels and a corresponding increase in SAH levels.

CONCLUSIONS

Ethanol binge after chronic ethanol altered the profile of site-specific histone modifications and may underlie the mechanism of augmented liver injury by chronic-ethanol-binge-treated rats.

In-vitro evaluation of chronic alcohol effects on expression of drug-metabolizing and drug-transporting proteins

Objectives

In alcoholics without alcoholic liver disease, boosted drug elimination has been reported. However, mechanistic explanations for this phenomenon remain uncertain. In particular, data on the potential role of drug transporters are sparse.

Methods

Using a well-established in-vitro model for induction of human drug-metabolizing and drug-transporting proteins, we evaluated the potency of ethanol and the major fermentation side-product isopentanol to alter expression and function of these proteins by quantitative real-time polymerase chain reaction, Western blotting and flow cytometry. P-glycoprotein (Pgp)-inhibiting properties of ethanol and isopentanol were investigated via calcein extrusion assay.

Key findings

Ethanol and isopentanol significantly changed expression levels of drug-metabolizing and drug-transporting proteins that normalized within 2 weeks upon withdrawal. Cytochrome P-450 2C19 and Pgp were most strongly induced. Ethanol-induced Pgp at the messenger RNA (mRNA) (twofold to eightfold) and protein level (twofold), but not at the functional level. Both compounds did not inhibit Pgp.

Conclusions

Ethanol is demonstrated to increase mRNA and protein expression of human drug transporters such as Pgp in vitro. Withdrawal of ethanol exposure causes return to non-induced conditions within weeks. Functional consequences of increased Pgp expression in alcoholics need to be evaluated by clinical trials applying selective Pgp substrates such as digoxin.

Induction of the liver cancer-down-regulated long noncoding RNA uc002mbe.2 mediates trichostatin-induced apoptosis of liver cancer cells

Differential expression of long non-coding RNAs (lncRNAs) plays critical roles in hepatocarcinogenesis. Considerable attention has focused on the antitumor effect of histone deacetylase inhibitor (Trichostatin A, TSA) as well as the coding gene expression-induced apoptosis of cancer cells. However, it is not known whether lncRNA has a role in TSA-induced apoptosis of human hepatocellular carcinoma (HCC) cells. The global expression of lncRNAs and coding genes was analyzed with the Human LncRNA Array V2.0 after 24 h treatment. Expression was verified in cell lines and tissues by quantitative real-time PCR. The data showed that 4.8% (959) of lncRNA and 6.1% (1849) of protein coding gene were significantly differentially expressed. The differential expressions of lncRNA and protein coding genes had distinguishable hierarchical clustering expression profiling pattern. Among these differentially expressed lncRNAs, the greatest change was noted for uc002mbe.2, which had more than 300 folds induction upon TSA treatment. TSA selectively induced uc002mbe.2 in four studied HCC cell lines. Compared with normal human hepatocytes and adjacent noncancerous tissues, uc002mbe.2 expression level was significantly lower in the HCC cell lines and liver cancer tissues. The TSA-induced uc002mbe.2 expression was positively correlated with the apoptotic effect of TSA in HCC cells. In addition, knockdown the expression of uc002mbe.2 significantly reduced TSA-induced apoptosis of Huh7cells. Therefore, TSA-induced apoptosis of HCC cells is uc002mbe.2 dependent and reduced expression of uc002mbe.2 may be associated with liver carcinogenesis.

Epigenetic-dependent regulation of drug transport and metabolism: an update

The pharmacokinetics of a drug are subject to large interindividual variability, which can result in lack of response or adverse drug reactions. In addition to genetic polymorphisms and drug interactions, key genes involved in the metabolism and transport of drugs are demonstrated to have epigenetic influences that can potentially affect interindividual variability in drug response. Emerging studies have focused on the importance of DNA methylation for ADME gene expression and for drug action and resistance, particularly in cancer. However, the epigenetic and ncRNA-dependent regulation of these genes, as well as the pharmacological consequences, is in need of greater attention. In the current review we provide an update of epigenetic and ncRNA-dependent regulation of ADME genes.

Association of liver stiffness with hepatic expression of pharmacokinetically important genes in alcoholic liver disease

BACKGROUND

Enhanced drug elimination in alcoholics remains largely indefinable. In contrast, the reduced elimination of drugs in patients with advanced alcoholic liver disease (ALD) is normally owing to hepatic end-stage disease such as cirrhosis. We here study the mRNA expression of various hepatic drug metabolizing enzymes and transporters in association with liver stiffness (LS) being a novel noninvasive parameter for the assessment of cirrhosis to unravel the dynamic relationship between ALD and determinants of pharmacokinetics such as drug metabolizing enzymes and transporters.

METHODS

We quantified mRNA expression levels of various cytochrome P-450 isoenzymes (CYPs) and drug transporters in 26 liver specimens of chronic alcoholics and 5 controls by quantitative polymerase chain reaction. In addition, liver histology, clinical data, and LS evaluated by transient elastography (Fibroscan) were obtained.

RESULTS

Eighteen patients had a normal or moderate LS < 8 kPa (69.2%), while in the remaining 8 patients (30.7%) advanced F3 or F4 fibrosis could be established with an LS > 8 kPa. Overall, CYP3A4, CYP2E1, and solute carrier organic anion transporter 1B1 (SLCO1B1) were negatively correlated with increasing LS. CYPs and drug transporters tended to be up-regulated in alcoholics without advanced fibrosis (LS < 8.0 kPa) compared to healthy controls supporting data of boosted drug elimination in alcoholics without advanced ALD. However, in alcoholics with severely increased LS (>8 kPa), expression levels of CYP2E1, SLC22A2, and SLCO1B1 were significantly lower.

CONCLUSIONS

In conclusion, CYPs and drug transporters seem to be induced in chronic alcoholics without irreversible liver damage but decline in case of manifest cirrhosis. Our study also suggests that noninvasive measurements of LS could be useful for pharmacokinetic predictions and individualized pharmacotherapy.

Noncoding microRNAs: small RNAs play a big role in regulation of ADME?

There are considerable interindividual variations in drug absorption, distribution, metabolism and excretion (ADME) in humans, which may lead to undesired drug effects in pharmacotherapy. Some of the mechanistic causes are known, e.g., genetic polymorphism, inhibition and induction of ADME enzymes and transporters, while others such as posttranscriptional regulation of ADME genes are under active study. MicroRNAs (miRNAs) are a large group of small, noncoding RNAs that control posttranscriptional expression of target genes. More than 1000 miRNAs have been identified in the human genome, which may regulate thousands of protein-coding genes. Some miRNAs directly or indirectly control the expression of xenobiotic-metabolizing cytochrome P450 enzymes, ATP-binding cassette or solute carrier transporters and/or nuclear receptors. Consequently, intervention of miRNA epigenetic signaling may alter ADME gene expression, change the capacity of drug metabolism and transport, and influence the sensitivity of cells to xenobiotics. In addition, the expression of some ADME regulatory miRNAs is significantly changed in cells following the exposure to a given drug, and the consequent changes in ADME gene expression might result in distinct ADME properties and drug response. In this review, we summarized recent findings on the role of noncoding miRNAs in epigenetic regulation of ADME genes and discussed the potential impact on pharmacokinetics and pharmacodynamics.

Epigenetic mechanisms in hepatocellular carcinoma: how environmental factors influence the epigenome

Epigenetic mechanisms maintain heritable changes in gene expression and chromatin organization over many cell generations. Importantly, deregulated epigenetic mechanisms play a key role in a wide range of human malignancies, including liver cancer. Hepatocellular carcinoma (HCC), which originates from the hepatocytes, is by far the most common liver cancer, with rates and aetiology that show considerable geographic variation. Various environmental agents and lifestyles known to be risk factors for HCC (such as infection by hepatitis B virus (HBV) and hepatitis C virus (HCV), chronic alcohol intake, and aflatoxins) are suspected to promote its development by eliciting epigenetic changes, however the precise gene targets and underlying mechanisms have not been elucidated. Many recent studies have exploited conceptual and technological advances in epigenetics and epigenomics to investigate the role of epigenetic events induced by environmental factors in HCC tumors and non-tumor precancerous (cirrhotic) lesions. These studies have identified a large number of genes and pathways that are targeted by epigenetic deregulation (changes in DNA methylation, histone modifications and RNA-mediated gene silencing) during the development and progression of HCC. Frequent identification of aberrant epigenetic changes in specific genes in cirrhotic tissue is consistent with the notion that epigenetic deregulation of selected genes in pre-malignant lesions precedes and promotes the development of HCC. In addition, several lines of evidence argue that some environmental factors (such as HBV virus) may abrogate cellular defense systems, induce silencing of host genes and promote HCC development via an "epigenetic strategy". Finally, profiling studies reveal that HCC tumors and pre-cancerous lesions may exhibit epigenetic signatures associated with specific risk factors and tumor progression stage. Together, recent evidence underscores the importance of aberrant epigenetic events induced by environmental factors in liver cancer and highlights potential targets for biomarker discovery and future preventive and therapeutic strategies.

Enrichment of Nur77 mediated by retinoic acid receptor β leads to apoptosis of human hepatocellular carcinoma cells induced by fenretinide and histone deacetylase inhibitors

The synthetic retinoid fenretinide is one of the most promising clinically tested retinoids. Previously, we have shown that fenretinide induces apoptosis of Huh7 cells, but HepG2 cells are relatively resistant to fenretinide-induced apoptosis. This study examines the interactive role of fenretinide and histone deacetylase inhibitors (HDACi) in inducing apoptosis of human hepatocellular carcinoma (HCC) cells and the underlying mechanism. Trichostatin A and scriptaid can either enhance fenretinide-induced apoptosis in the fenretinide sensitive HCC cells (Huh7 and Hep3B) or sensitize the fenretinide resistant cells (HepG2) to become sensitive to the apoptotic effect of fenretinide in a cancer cell-specific manner. The sensitivity of cells to fenretinide-induced apoptosis was not associated with reactive oxygen species production nor with antioxidant gene expression. However, the level of retinoic acid receptor β (RARβ) and Nur77 (NR4A1) was important for inducing apoptosis. Upon fenretinide and HDACi treatment, the expression of RARβ and Nur77 were induced and colocalized in the cytosol. The induction of Nur77 protein level, but not the messenger RNA level, was RARβ-dependent. In addition, RARβ interacted with Nur77. Nur77 was essential for fenretinide-induced and HDACi-induced apoptosis of Huh7 cells. Induction of the expression, the interaction, and the nuclear export of RARβ and Nur77 mediate fenretinide-induced and HDACi-induced apoptosis.

CONCLUSION

Our findings suggest that targeting Nur77 and RARβ simultaneously provides an effective way to induce HCC cell death.