Chemoprevention of hepatocellular carcinoma in chronic hepatitis C

Polysaccharide-Rich Fractions from Ganoderma resinaceum (Ganodermataceae) as Chemopreventive Agents in N-Diethylnitrosamine-Induced Hepatocellular Carcinoma in Wistar Rats

Hepatocellular carcinoma (HCC) is one of the most common and lethal diseases worldwide. Its treatment remains ineffective and the prognosis remains severe, thus favoring the emergence of a preventive approach. Mushroom-derived polysaccharides offer great opportunities because of their less toxicity and bioactivities. The present study aimed to investigate the chemopreventive effects of water-soluble polysaccharides from Ganoderma resinaceum on HCC. Two G. resinaceum polysaccharide-rich fractions (GRP I and GRP II) were obtained following hot water and alcohol precipitation. Their proteins, phenol compounds, and total neutral sugar content were assayed. The in vitro antiproliferative effect was assessed in MDA-MB 231, Hela, and HepG₂ using the MTT assay. Further, for the in vivo study, seven groups of nine rats each received N-diethylnitrosamine (100 mg/kg BW), vehicle (NaCl 0.9%), doxorubicin (10 mg/kg BW), or G. resinaceum polysaccharides (125 and 250 mg/kg BW). Liver cancer initiation and progression was assessed by evaluating histomorphology of liver section, hepatic injury markers, hematology, cytokines/chemokines levels, and stress oxidative markers. GRP II presented higher protein and sugar and lower phenol compound content than GRP I. GRP exhibited CC₅₀ of 340 and 261.7 in HepG₂ cells after 48 h. Moreover, GRP I and GRP II (125 and 250 mg/kg) prevented the alteration of the histoarchitecture of the liver induced by the DEN. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alpha-fetoprotein (AFP), proinflammatory cytokines (G-CSF, IFNγ, and TNFα), and chemokines (eotaxin and fractalkine) levels were significantly decreased in the GRP I- and GRP II-treated groups, while anti-inflammatory cytokines (IL-10 and IL-12p70) levels were increased. The antioxidant defense was also stimulated by reducing malondialdehyde (MDA) and nitric oxide (NO₂) levels, increasing catalase (CAT) and superoxide dismutase (SOD) activities, and reducing glutathione (GSH) levels. Our results indicate that GRP I exhibits chemopreventive effects by inhibiting cell proliferation and restoring liver architecture, antioxidant enzymes, and cytokines/chemokines balance.

Cystathionine β-Synthase in Physiology and Cancer

Cystathionine β-synthase (CBS) regulates homocysteine metabolism and contributes to hydrogen sulfide (H₂S) biosynthesis through which it plays multifunctional roles in the regulation of cellular energetics, redox status, DNA methylation, and protein modification. Inactivating mutations in CBS contribute to the pathogenesis of the autosomal recessive disease CBS-deficient homocystinuria. Recent studies demonstrating that CBS promotes colon and ovarian cancer growth in preclinical models highlight a newly identified oncogenic role for CBS. On the contrary, tumor-suppressive effects of CBS have been reported in other cancer types, suggesting context-dependent roles of CBS in tumor growth and progression. Here, we review the physiological functions of CBS, summarize the complexities regarding CBS research in oncology, and discuss the potential of CBS and its key metabolites, including homocysteine and H₂S, as potential biomarkers for cancer diagnosis or therapeutic targets for cancer treatment.

Chinese medicines for prevention and treatment of human hepatocellular carcinoma: current progress on pharmacological actions and mechanisms

Hepatocellular carcinoma (HCC) is one of leading causes of death in the world. Although various treatments have been developed, the therapeutic side effects are far from desirable. Chinese medicines (CMs, including plants, animal parts and minerals) have drawn a great deal of attention in recent years for their potential in the treatment of HCC. Most studies have shown that CMs may be able to retard HCC progression with multiple actions, either alone or in combination with other conventional therapies to improve quality of life in HCC patients. Additionally, CMs are used for preventing HCC occurrence. The aim of this study is to review the potential prophylactic and curative effects of CMs on human HCC and the possible mechanisms that underlie these pharmacological actions. Publications were collected and reviewed from PubMed and China National Knowledge Infrastructure from 2000 to 2014. Keywords for literature searches include "Chinese medicine", "Chinese herb", "traditional Chinese Medicine", "hepatocellular carcinoma" and "liver cancer". CMs in forms of pure compounds, isolated fractions, and composite formulas are included. Combination therapies are also considered. Both in vitro and in vivo efficacies of CMs are being discussed and the translational potential to bedside is to be discussed with clinical cases, which show the actions of CMs on HCC may include tumor growth inhibition, antimetastatic activities, anti-inflammation, anti-liver cancer stem cells, reversal on multi-drug resistance and induction/reduction of oxidative stress. Multiple types of molecules are found to contribute in the above actions. The review paper indicated that CMs might have potential to both prevent HCC occurrence and retard HCC progression with several molecular targets involved.

Chemoprevention of Diethylnitrosamine-Initiated and Phenobarbital-Promoted Hepatocarcinogenesis in Rats by Sulfated Polysaccharides and Aqueous Extract of Ulva lactuca

Hepatocellular carcinoma (HCC) is one of the common cancers and lethal diseases worldwide. Both oxidative stress and chronic inflammation contribute to the pathogenesis of HCC. Because of limited treatment options and a grave prognosis of HCC, preventive management has been emphasized. The marine macroalgae Ulva lactuca (Ulvaceae) is consumed by humans and livestock because of its nutritional value. Recent studies showed that various extracts of U. lactuca possess antiviral, antiplasmodial, antinephrotoxic, antioxidant, and anti-inflammatory properties. However, very limited information is available on anticancer potential of U. lactuca with no reports on liver cancer chemopreventive efficacy of this marine algae. Accordingly, the present study was initiated to evaluate the possible antihepatocarcinogenic effects and antioxidant mechanisms of action of various U. lactuca extracts against a clinically relevant rodent model of HCC. Initiation of hepatocarcinogenesis was performed in Sprague-Dawley rats by a single injection of dietary carcinogen diethylnitrosamine (DENA, 200 mg/kg, intraperitoneally), followed by promotion with phenobarbital (0.05%) in drinking water. The rats were fed with daily oral dose (50 mg/kg) of polysaccharide sulfate or aqueous extract of U. lactuca for 2, 12, and 24 weeks. At these timepoints, blood samples were taken to measure hepatic injury markers, including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, γ-glutamyl transferase, and bilirubin. The liver tissue was harvested for measurement of hepatic oxidative indices, including lipid peroxidation, reduced glutathione, nitric oxide, catalase, superoxide dismutase, glutathione reductase, and glutathione S-transferase. Hepatic histopathology, immunohistochemical analysis of cell proliferation and apoptosis by DNA fragmentation assay were performed. Our results clearly indicate that sulfated polysaccharides of U. lactuca exert a marked chemoprevention of DENA-initiated hepatocarcinogenesis through inhibition of abnormal cell proliferation and induction of apoptosis. A modest inhibition rat liver carcinogenesis was observed with the aqueous extract. The sulfated polysaccharides altered serum parameters of hepatic damage and modulated various components of the hepatic enzymatic and nonenzymatic antioxidant defense systems. The sulfated polysaccharides from U. lactuca may have unique properties of providing protection against DENA-induced oxidative stress which could contribute to chemoprevention of experimental hepatocarcinogenesis. U. lactuca sulfated polysaccharides could be developed as chemopreventive and therapeutic drug against human HCC.

Silymarin and hepatocellular carcinoma: a systematic, comprehensive, and critical review

The blessed milk thistle (Silybum marianum L.), a flowering plant native to Mediterranean Europe, has been consumed and extensively used as a cure for various chronic liver ailments over several centuries. Milk thistle extract, known as silymarin, is a complex mixture of seven major flavonolignans and one flavonoid. The phytoconstituents of silymarin owe their therapeutic and hepatoprotective effects to their strong antioxidant and anti-inflammatory properties. Primary liver cancer, also known as hepatocellular carcinoma (HCC), occurs in a milieu of oxidative stress and inflammation. The etiology of HCC includes chronic infection with hepatitis B and C viruses, cirrhosis, and exposure to dietary and environmental hepatocarcinogens. Current therapeutic options for HCC, including surgical resection and liver transplantation, have limited benefits and are essentially ineffective. Chemoprevention, using phytochemicals with potent antioxidant and anti-inflammatory properties, represents a fascinating strategy, which has been a subject of intense investigation in the recent years. In this review, we explore the potential role of silymarin as a chemopreventive and therapeutic agent for HCC. The review systematically evaluates the preclinical in-vitro and in-vivo studies investigating the effects of silymarin and its constituents on HCC. The biochemical mechanisms involved in the anti-liver-cancer effects of silymarin have been presented. The current status of clinical studies evaluating the potential of role of silymarin in liver cancer, especially that caused by hepatitis C virus, has also been examined. Potential challenges and future directions of research involved in the 'bench-to-bedside' transition of silymarin phytoconstituents for the chemoprevention and treatment of HCC have also been discussed.

Prevention of hepatocellular carcinoma: Focusing on antioxidant therapy

Oxidative stress has been investigated in the context of alcoholic liver injury for many years and shown to be a causal factor of chronic hepatitis C (CHC), nonalcoholic steatohepatitis (NASH), drug-induced liver injury, Wilson’s disease, and hemochromatosis. In CHC, it has been demonstrated that oxidative stress plays an important role in hepatocarcinogenesis. In cases with persistent hepatitis due to failure of hepatitis C virus eradication, or chronic liver disease, such as NASH, the treatment of which remains unestablished, it is important to reduce serum alanine aminotransferase levels and prevent liver fibrosis and development of hepatocellular carcinoma. This also suggests the importance of antioxidant therapy. Among treatment options where it would be expected that anti-inflammatory activity plays a role in their confirmed efficacy for chronic hepatitis, iron depletion therapy, glycyrrhizin, ursodeoxycholic acid, Sho-Saiko-To, and vitamin E can all be considered antioxidant therapies. To date, however, the ability of these treatments to prevent cancer has been confirmed only in CHC. Nevertheless, anti-inflammatory and anti-fibrotic effects have been demonstrated in other liver diseases and these therapies may potentially be effective for cancer prevention.

Cell death and cell death responses in liver disease: mechanisms and clinical relevance

Hepatocellular death is present in almost all types of human liver disease and is used as a sensitive parameter for the detection of acute and chronic liver disease of viral, toxic, metabolic, or autoimmune origin. Clinical data and animal models suggest that hepatocyte death is the key trigger of liver disease progression, manifested by the subsequent development of inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Modes of hepatocellular death differ substantially between liver diseases. Different modes of cell death such as apoptosis, necrosis, and necroptosis trigger specific cell death responses and promote progression of liver disease through distinct mechanisms. In this review, we first discuss molecular mechanisms by which different modes of cell death, damage-associated molecular patterns, and specific cell death responses contribute to the development of liver disease. We then review the clinical relevance of cell death, focusing on biomarkers; the contribution of cell death to drug-induced, viral, and fatty liver disease and liver cancer; and evidence for cell death pathways as therapeutic targets.

Sho-saiko-to, a traditional herbal medicine, regulates gene expression and biological function by way of microRNAs in primary mouse hepatocytes

BACKGROUND

Sho-saiko-to (SST) (also known as so-shi-ho-tang or xiao-chai-hu-tang) has been widely prescribed for chronic liver diseases in traditional Oriental medicine. Despite the substantial amount of clinical evidence for SST, its molecular mechanism has not been clearly identified at a genome-wide level.

METHODS

By using a microarray, we analyzed the temporal changes of messenger RNA (mRNA) and microRNA expression in primary mouse hepatocytes after SST treatment. The pattern of genes regulated by SST was identified by using time-series microarray analysis. The biological function of genes was measured by pathway analysis. For the identification of the exact targets of the microRNAs, a permutation-based correlation method was implemented in which the temporal expression of mRNAs and microRNAs were integrated. The similarity of the promoter structure between temporally regulated genes was measured by analyzing the transcription factor binding sites in the promoter region.

RESULTS

The SST-regulated gene expression had two major patterns: (1) a temporally up-regulated pattern (463 genes) and (2) a temporally down-regulated pattern (177 genes). The integration of the genes and microRNA demonstrated that 155 genes could be the targets of microRNAs from the temporally up-regulated pattern and 19 genes could be the targets of microRNAs from the temporally down-regulated pattern. The temporally up-regulated pattern by SST was associated with signaling pathways such as the cell cycle pathway, whereas the temporally down-regulated pattern included drug metabolism-related pathways and immune-related pathways. All these pathways could be possibly associated with liver regenerative activity of SST. Genes targeted by microRNA were moreover associated with different biological pathways from the genes not targeted by microRNA. An analysis of promoter similarity indicated that co-expressed genes after SST treatment were clustered into subgroups, depending on the temporal expression patterns.

CONCLUSIONS

We are the first to identify that SST regulates temporal gene expression by way of microRNA. MicroRNA targets and non-microRNA targets moreover have different biological roles. This functional segregation by microRNA would be critical for the elucidation of the molecular activities of SST.

New insights on the role of epigenetic alterations in hepatocellular carcinoma

Emerging evidence assigns to epigenetic mechanisms heritable differences in gene function that come into being during cell development or via the effect of environmental factors. Epigenetic deregulation is strongly involved in the development of hepatocellular carcinoma (HCC). It includes changes in methionine metabolism, promoter hypermethylation, or increased proteasomal degradation of oncosuppressors, as well as posttranscriptional deregulation by microRNA or messenger RNA (mRNA) binding proteins. Alterations in the methylation of the promoter of methyl adenosyltransferase MAT1A and MAT2A genes in HCC result in decreased S-adenosylmethionine levels, global DNA hypomethylation, and deregulation of signal transduction pathways linked to methionine metabolism and methyl adenosyltransferases activity. Changes in S-adenosylmethionine levels may also depend on MAT1A mRNA destabilization associated with MAT2A mRNA stabilization by specific proteins. Decrease in MAT1A expression has also been attributed to miRNA upregulation in HCC. A complex deregulation of miRNAs is also strongly involved in hepatocarcinogenesis, with up-regulation of different miRNAs targeting oncosuppressor genes and down-regulation of miRNAs targeting genes involved in cell-cycle and signal transduction control. Oncosuppressor gene down-regulation in HCC is also induced by promoter hypermethylation or posttranslational deregulation, leading to proteasomal degradation. The role of epigenetic changes in hepatocarcinogenesis has recently suggested new promising therapeutic approaches for HCC on the basis of the administration of methylating agents, inhibition of methyl adenosyltransferases, and restoration of the expression of tumor-suppressor miRNAs.

Pleiotropic effects of methionine adenosyltransferases deregulation as determinants of liver cancer progression and prognosis

Downregulation of liver-specific MAT1A gene, encoding S-adenosylmethionine (SAM) synthesizing isozymes MATI/III, and upregulation of widely expressed MAT2A, encoding MATII isozyme, known as MAT1A:MAT2A switch, occurs in hepatocellular carcinoma (HCC). Being inhibited by its reaction product, MATII isoform upregulation cannot compensate for MATI/III decrease. Therefore, MAT1A:MAT2A switch contributes to decrease in SAM level in rodent and human hepatocarcinogenesis. SAM administration to carcinogen-treated rats prevents hepatocarcinogenesis, whereas MAT1A-KO mice, characterized by chronic SAM deficiency, exhibit macrovesicular steatosis, mononuclear cell infiltration in periportal areas, and HCC development. This review focuses upon the pleiotropic changes, induced by MAT1A/MAT2A switch, associated with HCC development. Epigenetic control of MATs expression occurs at transcriptional and post-transcriptional levels. In HCC cells, MAT1A/MAT2A switch is associated with global DNA hypomethylation, decrease in DNA repair, genomic instability, and signaling deregulation including c-MYC overexpression, rise in polyamine synthesis, upregulation of RAS/ERK, IKK/NF-kB, PI3K/AKT, and LKB1/AMPK axis. Furthermore, decrease in MAT1A expression and SAM levels results in increased HCC cell proliferation, cell survival, and microvascularization. All of these changes are reversed by SAM treatment in vivo or forced MAT1A overexpression or MAT2A inhibition in cultured HCC cells. In human HCC, MAT1A:MAT2A and MATI/III:MATII ratios correlate negatively with cell proliferation and genomic instability, and positively with apoptosis and global DNA methylation. This suggests that SAM decrease and MATs deregulation represent potential therapeutic targets for HCC. Finally, MATI/III:MATII ratio strongly predicts patients' survival length suggesting that MAT1A:MAT2A expression ratio is a putative prognostic marker for human HCC.

Effects of coffee consumption in chronic hepatitis C: a randomized controlled trial

BACKGROUND

Coffee is associated with a reduced risk of hepatocellular carcinoma in patients with chronic C hepatitis. This prospective trial was aimed at assessing the mechanisms underlying coffee-related protective effects.

METHODS

Forty patients with chronic hepatitis C were randomized into two groups: the first consumed 4 cups of coffee/day for 30 days, while the second remained coffee "abstinent". At day 30, the groups were switched over for a second month.

RESULTS

At baseline, aspartate aminotransferase and alanine aminotransferase were lower in patients drinking 3-5 (Group B) than 0-2 cups/day (Group A) (56 ± 6 vs 74 ± 11/60 ± 3 vs 73 ± 7 U/L p=0.05/p=0.04, respectively). HCV-RNA levels were significantly higher in Group B [(6.2 ± 1.5) × 10(5)vs (3.9 ± 1.0) × 10(5)UI/mL, p=0.05]. During coffee intake, 8-hydroxydeoxyguanosine and collagen levels were significantly lower than during abstinence (15 ± 3 vs 44 ± 16 8-hydroxydeoxyguanosine/10(5)deoxyguanosine, p=0.05 and 56 ± 9 vs 86 ± 21 ng/mL, p=0.04). Telomere length was significantly higher in patients during coffee intake (0.68 ± 0.06 vs 0.48 ± 0.04 Arbitrary Units, p=0.006). Telomere length and 8-hydroxydeoxyguanosine were inversely correlated.

CONCLUSION

In chronic hepatitis C coffee consumption induces a reduction in oxidative damage, correlated with increased telomere length and apoptosis, with lower collagen synthesis, factors that probably mediate the protection exerted by coffee with respect to disease progression.

Pomegranate Bioactive Constituents Suppress Cell Proliferation and Induce Apoptosis in an Experimental Model of Hepatocellular Carcinoma: Role of Wnt/ β -Catenin Signaling Pathway

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide, and chemoprevention represents a viable approach in lowering the mortality of this disease. Pomegranate fruit, an abundant source of anti-inflammatory phytochemicals, is gaining tremendous attention for its wide-spectrum health benefits. We previously reported that a characterized pomegranate emulsion (PE) prevents diethylnitrosamine (DENA)-induced rat hepatocarcinogenesis though inhibition of nuclear factor-kappaB (NF- κ B). Since NF- κ B concurrently induces Wnt/ β -catenin signaling implicated in cell proliferation, cell survival, and apoptosis evasion, we examined antiproliferative, apoptosis-inducing and Wnt/ β -catenin signaling-modulatory mechanisms of PE during DENA rat hepatocarcinogenesis. PE (1 or 10 g/kg) was administered 4 weeks before and 18 weeks following DENA exposure. There was a significant increase in hepatic proliferation (proliferating cell nuclear antigen) and alteration in cell cycle progression (cyclin D1) due to DENA treatment, and PE dose dependently reversed these effects. PE substantially induced apoptosis by upregulating proapoptotic protein Bax and downregulating antiapoptotic protein Bcl-2. PE dose dependently reduced hepatic β -catenin and augmented glycogen synthase kinase-3 β expression. Our study provides evidence that pomegranate phytochemicals exert chemoprevention of hepatic cancer through antiproliferative and proapoptotic mechanisms by modulating Wnt/ β -catenin signaling. PE, thus, targets two interconnected molecular circuits (canonical NF- κ B and Wnt/ β -catenin pathways) to exert chemoprevention of HCC.

S-adenosylmethionine in liver health, injury, and cancer

S-adenosylmethionine (AdoMet, also known as SAM and SAMe) is the principal biological methyl donor synthesized in all mammalian cells but most abundantly in the liver. Biosynthesis of AdoMet requires the enzyme methionine adenosyltransferase (MAT). In mammals, two genes, MAT1A that is largely expressed by normal liver and MAT2A that is expressed by all extrahepatic tissues, encode MAT. Patients with chronic liver disease have reduced MAT activity and AdoMet levels. Mice lacking Mat1a have reduced hepatic AdoMet levels and develop oxidative stress, steatohepatitis, and hepatocellular carcinoma (HCC). In these mice, several signaling pathways are abnormal that can contribute to HCC formation. However, injury and HCC also occur if hepatic AdoMet level is excessive chronically. This can result from inactive mutation of the enzyme glycine N-methyltransferase (GNMT). Children with GNMT mutation have elevated liver transaminases, and Gnmt knockout mice develop liver injury, fibrosis, and HCC. Thus a normal hepatic AdoMet level is necessary to maintain liver health and prevent injury and HCC. AdoMet is effective in cholestasis of pregnancy, and its role in other human liver diseases remains to be better defined. In experimental models, it is effective as a chemopreventive agent in HCC and perhaps other forms of cancer as well.

Caffeinated and decaffeinated coffee and tea intakes and risk of colorectal cancer in a large prospective study

BACKGROUND

Coffee and tea are widely consumed globally and are rich sources of potential chemopreventive compounds. Epidemiologic data for coffee and tea intakes in relation to colorectal cancer remain unclear. Despite differences in gut physiology, few studies have conducted investigations by anatomic subsites.

OBJECTIVE

We evaluated coffee and tea intakes (caffeinated and decaffeinated) in relation to colon (proximal and distal) and rectal cancers.

DESIGN

The NIH-AARP Diet and Health Study included 489,706 men and women who completed a baseline (1995-1996) self-administered questionnaire of demographics, diet, and lifestyle. Over a median of 10.5 y of follow-up, we identified 2863 proximal colon, 1993 distal colon, and 1874 rectal cancers. Multivariable HRs and 95% CIs were estimated by using Cox regression.

RESULTS

Approximately 16% of participants drank ≥4 cups coffee/d. Compared with nondrinkers, drinkers of 4-5 cups coffee/d (HR: 0.85; 95% CI: 0.75, 0.96) and ≥6 cups coffee/d (HR: 0.74; 95% CI: 0.61, 0.89; P-trend < 0.001) had a lower risk of colon cancer, particularly of proximal tumors (HR for ≥6 cups/d: 0.62; 95% CI: 0.49, 0.81; P-trend < 0.0001). Results were similar to those overall for drinkers of predominantly caffeinated coffee. Although individual HRs were not significant, there was a significant P-trend for both colon and rectal cancers for people who drank predominantly decaffeinated coffee. No associations were observed for tea.

CONCLUSIONS

In this large US cohort, coffee was inversely associated with colon cancer, particularly proximal tumors. Additional investigations of coffee intake and its components in the prevention of colorectal cancer by subsites are warranted. The NIH-AARP Diet and Health Study was registered at clinicaltrials.gov as NCT00340015.

Association of IL28B SNP With Progression of Egyptian HCV Genotype 4 Patients to End Stage Liver Disease

BACKGROUND

IL28B single nucleotide polymorphisms (SNPs) play important roles in the management of hepatitis C virus (HCV) infections and are strongly associated with spontaneous and treatment-induced HCV clearance.

OBJECTIVES

In the present study, the association between IL28B variants and the progression of HCV infection in Egyptian patients infected with type 4a virus will be examined.

PATIENTS AND METHODS

Frequencies of the protective genotype C/C of SNP, rs12979860 were determined in healthy subjects, spontaneous resolvers, and chronic HCV type 4 patients with low F scores and in patients with end stage liver disease (ESLD). This study included a total of 404 subjects. Patients infected with HCV type 4a (n = 304) were divided into; chronic hepatitis C (CHC) with low F scores (CHC, n = 110), end stage liver disease (n = 110), liver cirrhosis (LC) (n = 35) and hepatocellular carcinoma (HCC) patients (n = 75), spontaneous resolvers of HCV infection (n = 84) were also included. A healthy group representing the Egyptian population (n = 100) was also included in the genotyping of IL28B. The later was typed via a polymerase chain reaction based restriction fragment length polymorphism (PCR-RFLP) assay analysis on purified genomic DNA extracted from all individuals.

RESULTS

A significant increase (P < 0.0005) was observed in frequencies of IL-28B rs12979860 C/C genotypes in the healthy population, than in the CHC, LC and HCC groups (C/C = 48%, 13%, 0%.and 0% respectively). On the other hand the C/C genotype was significantly higher (P < 0.0005) in spontaneous resolvers than in healthy subjects. A comparable significant increase in the frequency of C/T allele accompanied by mild elevation of T/T allele frequency, were detected along the progression towards ESLD.

CONCLUSIONS

Genotype C/C is associated with viral clearance during acute infection. The sharp decline in the C/C genotype from healthy to CHC subjects and the total absence of the C/C genotype in ESLD suggests a central role of this genotype against HCV disease progression.

The retinoid X receptors and their ligands

This chapter presents an overview of the current status of studies on the structural and molecular biology of the retinoid X receptor subtypes α, β, and γ (RXRs, NR2B1-3), their nuclear and cytoplasmic functions, post-transcriptional processing, and recently reported ligands. Points of interest are the different changes in the ligand-binding pocket induced by variously shaped agonists, the communication of the ligand-bound pocket with the coactivator binding surface and the heterodimerization interface, and recently identified ligands that are natural products, those that function as environmental toxins or drugs that had been originally designed to interact with other targets, as well as those that were deliberately designed as RXR-selective transcriptional agonists, synergists, or antagonists. Of these synthetic ligands, the general trend in design appears to be away from fully aromatic rigid structures to those containing partial elements of the flexible tetraene side chain of 9-cis-retinoic acid. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).