A study on prevention of bleeding complications using lusutrombopag for safe RFA in patients with hepatocellular carcinoma with low platelet counts: prospective observational study.

BACKGROUND: Platelet (PLT) transfusion was the most practical way to increase patients' PLT counts before invasive hepatic procedures such as radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC). A novel drug that raises the PLT count by acting on the thrombopoietin receptor has recently become available. METHODS: Lusutrombopag 3 mg was administered daily for 7 days to patients who underwent RFA for liver tumors with low PLT counts (< 50,000 PLT µL- 1). We collected demographic data concerning the patients' liver function and PLT counts. RESULTS: Lusutrombopag was administered to 91 patients, with a median age of 71 years (range 51-86). Forty-two patients had hepatitis C, 12 had hepatitis B, 21 had alcoholic liver disease, 11 had nonalcoholic steatohepatitis, and five had other diseases. The median Child-Pugh score was 7 (range 5-11). Thirty-seven patients had stage I tumors, 41 had Stage II, 12 had stage III, and one had stage IV. PLT count was elevated from 4.4 × 104 ± 1.4 × 104 to 8.6 × 104 ± 2.5 × 104 PLT µL- 1. Lusutrombopag administration prevented PLT transfusions in 84/91 patients (92%). No patient had bleeding complications after RFA. One had portal thrombosis after lusutrombopag administration. Patients who achieved PLT counts of > 50,000 PLT µL- 1 had higher PLT counts before lusutrombopag administration. The degree of splenomegaly did not affect the rate of PLT count elevation. There was no specific adverse effect by administrating lusutrombopag for patients with PLT counts of around 50,000 µL- 1 but > 50,000 µL- 1. CONCLUSIONS: Lusutrombopag administration before RFA was effective and seemed to be relatively safe for hepatocellular carcinoma patients with low PLT counts. TRIAL REGISTRATION: This study was approved by Japanese Red Cross Medical Center Institutional Reseach Comittie (#862, 07/03/2016), and was registered in a publically accessible primary register (#UMIN000046629, registered date: 14/01/2022).

Clinical features associated with radiological response to sorafenib in unresectable hepatocellular carcinoma: a large multicenter study in Japan.

BACKGROUND & AIMS: There have been no established predictive factors of responders to sorafenib in patients with unresectable hepatocellular carcinoma (HCC). This study aimed to investigate the factors predicting a good response to sorafenib in Japanese patients with HCC. METHODS: A total of 465 patients with unresectable HCC in the Japanese Red Cross Liver Study Group were treated with sorafenib between January 2008 and August 2013, and 316 patients with sufficient clinical data were analysed. To determine the factors predicting a good response, the relationships between radiological response and the following clinicopathological factors were analysed: age, gender, performance status, liver function, tumour status and decrease in serum alpha-foetoprotein (AFP) level after 1 month. RESULTS: This study included 259 males and 57 females with a median age of 70 years (range, 37-90 years), of which 191 (60.4%) were classified as Barcelona Clinic Liver Cancer stage C, and 271 (85.8%) had Child-Pugh class A liver function. The median overall survival time was 307 days and progression-free survival time was 109 days. According to the modified Response Evaluation Criteria In Solid Tumours, four patients achieved a complete response, 51 achieved a partial response, 136 had stable disease and 125 had progressive disease. Multivariate analysis identified female gender (P = 0.003) and decreased serum AFP level after 1 month (P = 0.042) as independent predictors of a complete or partial response. CONCLUSION: Our results suggest female gender and a decrease in serum AFP level are independent predictors of good response to sorafenib.

Proposal of Japan Red Cross score for sorafenib therapy in hepatocellular carcinoma.

AIM: There have been no established predictors of the outcome on sorafenib therapy for hepatocellular carcinoma (HCC) patients. We aimed to establish a new prognostic model suitable for sorafenib in HCC. METHODS: Among 465 HCC patients treated with sorafenib in 14 hospitals, we formed a training cohort with 270 patients at seven hospitals located in West Japan and a validation cohort with 167 patients at seven hospitals located in East Japan. In the training cohort, we examined the relationship between overall survival (OS) and pretreatment clinical factors, and structured a new prognostic model. We verified this model in the validation cohort and compared with four existing staging models. RESULTS: Multivariate analysis demonstrated distant metastases, portal invasion, intrahepatic tumor burden of more than 50%, serum α-fetoprotein of 150 ng/dL or more, des-γ-carboxyprothrombin of 1200 mAU/mL or more, albumin of 3.5 g/dL or less and total bilirubin of more than 1.0 mg/dL were significant independent adverse prognostic factors. We calculated a Japan Red Cross (JRC) score with these factors and classified three groups: low-, intermediate- or high-risk. Their median OS were well stratified (18.0, 8.8 and 3.7 months, respectively, P < 0.001) in the training cohort. In the validation cohort, OS were also statistically stratified (23.9, 10.3 and 2.9 months, P < 0.001). C-statistics of the JRC score was 0.755, the highest in the five models, indicating its novel predictability. CONCLUSION: Our proposed JRC score well predicts the prognosis of sorafenib therapy, and would be useful to plan individualized strategies for unresectable HCC.

Acute Liver Failure Due to Hypereosinophilic Syndrome Accompanied by Duodenal Perforation.

A 78-year-old woman presenting with severe acute liver failure was admitted to our hospital. On screening for the etiology of acute liver failure, it was diagnosed as being due to idiopathic hypereosinophilic syndrome (eosinophil count reported as 4766/µL; 33.8% of the white blood cells). Her medical history included marked eosinophilia, as observed six months prior to this admission. Corticosteroid therapy was initiated. During the clinical course, duodenal perforation occurred but was managed promptly by appropriate surgery. A liver biopsy, following the initiation of corticosteroid therapy, revealed degenerating hepatic cells with mild eosinophilic infiltration. With corticosteroid therapy, the liver function improved.

Double-stranded RNA-activated protein kinase inhibits hepatitis C virus replication but may be not essential in interferon treatment.

BACKGROUND: Double-stranded RNA-activated protein kinase (PKR), an interferon (IFN)-stimulated gene, is activated by binding with double-stranded RNA, a putative replicative intermediate of the hepatitis C virus (HCV). Activated PKR phosphorylates the alpha subunit of eukaryotic initiation factor-2 to inhibit the translation of viral protein. AIMS/METHODS: We established stable PKR knockdown Huh7 cells using RNA interference and investigated the effect of PKR against HCV replication using a subgenomic replicon that expressed luciferase reporter protein and the JFH1 full-length HCV genome. RESULTS: In stable PKR knockdown cells that harboured a subgenomic replicon, luciferase activity was approximately three times higher than that of control cells, indicating that the subgenomic replicon replicated with a higher efficiency in stable PKR knockdown cells than that in control cells. Furthermore, stable PKR knockdown cells secreted significantly more HCV particles than did control cells after transfection with the full-length HCV genome. The replication of the subgenomic replicon was suppressed by the addition of IFN-alpha in both cells. Although the extent of suppression was significantly lower in stable PKR knockdown than control cells using a low concentration (2.5-5 U/ml) of IFN-alpha, even 10 U/ml IFN-alpha suppressed the replication of subgenomic replicon by >98% in both cells. CONCLUSIONS: Double-stranded RNA-activated protein kinase plays an important role in suppressing HCV replication in an innate state, but may not be essential in IFN therapy.

Potential contribution of tumor suppressor p53 in the host defense against hepatitis C virus.

UNLABELLED: Infection by hepatitis C virus (HCV) usually results into chronic hepatitis that can ultimately lead to cirrhosis and hepatocellular carcinoma. Type 1 interferons (IFN-alpha/beta) constitute the primary cellular defense against viral infection including HCV. IFN binding to their receptors activates associated Jak1 and Tyk2 kinases, which ultimately leads to phosphorylation and assembly of a signal transducer and activator of transcription protein (STAT)1-STAT2-interferon regulatory factor (IRF)9 trimetric complex called interferon-stimulated gene factor 3 that translocates into the nucleus and binds to the interferon- stimulated response elements (ISRE), leading to transcriptional induction of several antiviral genes, including double-stranded RNA-activated protein kinase (PKR), 2',5'- oligoadenylate synthetase (OAS), and myxovirus resistance protein A (MxA). Understanding the mechanisms of how the virus evades this cellular innate defense and establishes a chronic infection is the key for the development of better therapeutics against HCV infection. Here, we demonstrate that p53 could have a crucial role in the cellular innate defense against HCV. We observed significantly higher levels of HCV RNA replication and viral protein expression in the Huh7 cells when their p53 expressions were knocked down. Moreover, IFN treatment was less effective in inhibiting the HCV RNA replication in the p53-knocked-down (p53kd) Huh7 cells. In fact, the activation of the ISRE and the induction of ISGs were significantly attenuated in the p53kd Huh7 cells and p53 was found to directly interact with IRF9. CONCLUSION: These observations underscore the potential contributions of the tumor suppressor p53 in cellular antiviral immunity against HCV with possible therapeutic implications.

Gene expressions associated with chemosensitivity in human hepatoma cells.

BACKGROUND/AIMS: Only limited patients with hepatoma benefit from chemotherapy without a clear explanation. We aimed to identify genes associated with chemosensitivity using transcriptional profiles. METHODOLOGY: In 8 hepatoma cells (HLE, HLF, Huh7, Hep3B, PLC/PRF/5, SK-Hep1, Huh6, and HepG2) transcriptional profiles were obtained using cDNA microarray including 2300 genes. Chemosensitivities to 8 anticancer drugs (nimustine, mitomycin C, cisplatin, carboplatin, doxorubicin, epirubicin, mitoxantrone, and 5-fluorouracil) were measured by obtaining 50% growth inhibitory concentrations (GI50) using MTT assay. Genes having drug-specific association with chemosensitivity were selected. RESULTS: Up-regulation of topoisomerase II beta was associated with chemo-resistance, the target of doxorubicin. Platinum-specific resistance was associated with superoxide dismutase 2 expression. Antigen peptide transporter 1 expression correlated with nimustine and mitoxantrone-specific susceptibility. These results were verified by semi-quantitative RT-PCR. Drug inactivators reported in non-liver cancers such as multidrug transporters and drug metabolizers showed less diversity of chemosensitivity in hepatoma cells. CONCLUSIONS: To evaluate these gene expressions may be useful to select anticancer drugs, and possibly to consider new therapeutic target to modify drug action.

Early Gastric Cancer Recurrence Following Curative Resection Presenting as Biliary Tract Dilatation, Pancreatic Duct Dilatation and Intestinal Wall Thickening.

Early gastric cancer, especially cancer confined to the mucosa (stage T1a), is known to have a high cure rate with rare recurrence. We herein report the case of a 40-year-old female who initially presented with biliary tract dilatation, pancreatic duct dilatation and intestinal wall thickening 3 years after curative resection of pT1aN0 stage gastric cancer. The intestinal resection specimen revealed tumor cells spreading through the subserosa to the submucosa sparing mucosal membrane, which made exploratory laparotomy the only approach to confirm the diagnosis. It is always important to be aware of malignancy recurrence and clinicians should not hesitate to choose exploratory laparotomy to avoid any delay in the diagnosis and treatment.

Vitamin K2 binds 17beta-hydroxysteroid dehydrogenase 4 and modulates estrogen metabolism.

Vitamin K is a cofactor for gamma-glutamyl carboxylase, an enzyme that is important for blood coagulation. Recent studies have shown that vitamin K has other roles, in addition to post-transcriptional modification, such as bone metabolism and antitumoral actions; these findings have indicated that there might be unknown intracellular binding proteins that are specific for vitamin K. In this study, vitamin K-binding proteins were characterized by pull-down experiment using a chemically synthesized biotynylated vitamin K followed by mass spectrometric identification of the pull-downed components. The results indicated that 17beta hydroxy steroid dehydrogenase 4, apolipoportein E, and 40S ribosomal proteins S7 and S13 might be the candidates of the vitamin K-binding proteins. Subsequent experiments showed that vitamin K2 binds 17beta hydroxysteroid dehydrogenase 4 and decreases the intracellular estradiol:estrone ratio, which resulted in the inhibition of the amount of estrogen receptor alpha-binding to its target DNA. These results suggest a possible novel role for vitamin K in modulating estrogen function.

UDP-glucuronosyltransferase 1A7 genetic polymorphisms are associated with hepatocellular carcinoma in japanese patients with hepatitis C virus infection.

PURPOSE: Genetic polymorphisms of UDP-glucuronosyltransferase 1A7 (UGT1A7), which detoxifies endogenous and environmental carcinogens, have been reported to be associated with hepatocellular carcinoma (HCC) in German populations. On the other hand, we reported that interleukin-1 beta (IL-1 beta) gene polymorphisms were associated with hepatitis C virus (HCV)-related HCC. In this study, we evaluated the association of both genes with the risk of HCC in Japanese HCV-infected patients. EXPERIMENTAL DESIGN: Genetic polymorphisms of UGT1A7 and IL-1 beta were investigated in 280 Japanese patients (122 with HCC and 158 without HCC) with chronic HCV infections, by use of standard PCR-based genotyping techniques. RESULTS: We designated the UGT1A7*1 allele (a haplotype conferring higher activity) as H and the *2, *3, and *4 alleles (haplotypes conferring lower activity) as L. The proportions of UGT1A7 L/L and H/L alleles (genotypes) in patients with HCC (25% and 45%, respectively) were higher than those in patients without HCC (15% and 39%, respectively) with odds ratios of 2.73 (95% confidence interval, 1.40-5.35) and 1.80 (95% confidence interval, 1.05-3.09), respectively, compared with the UGT1A7 H/H alleles. Multivariate analyses revealed that UGT1A7 L/L and IL-1 beta/-31T/T-511C/C genotypes, the presence of cirrhosis, age >60 years, male sex, and alpha-fetoprotein >20 microg/ml were associated with the presence of HCC (odds ratios, 2.33, 2.67, 4.20, 3.12, 3.09, and 2.90, respectively). CONCLUSION: The UGT1A7 polymorphisms together with IL-1 beta were associated with the presence of HCC in Japanese HCV-infected patients.

Hepatic gene expression profiles associated with fibrosis progression and hepatocarcinogenesis in hepatitis C patients.

AIM: To determine fibrosis progression and hepatocellular carcinoma (HCC), using simultaneous gene expression analysis. METHODS: Total RNA samples were extracted from liver biopsies from 19 patients with hepatitis C virus (HCV) infection and 3 patients without HCV infection. Among the 19 HCV-infected patients, 7 and 12 patients had grade F1-2 and F3-4 fibrosis, respectively. Of the 12 patients with F3-4 fibrosis, 8 had HCC. Gene expression in the liver samples was determined using an oligonucleotide microarray. The following comparisons were performed: normal livers vs HCV-infected livers; F1-2 vs F3-4; and F3-4 with HCC vs F3-4 without HCC. Genes that were differentially expressed between these groups were identified based on signal-to-noise ratios. RESULTS: In the HCV-infected livers, genes involved in immune responses were highly expressed. Expression levels of genes for plasma proteins and drug-metabolizing enzymes were decreased and those of genes involved in the cell cycle and oncogenesis were increased in the F3-4 cases as compared to the F1-2 cases. Among the F3-4 cases, genes involved in carbohydrate metabolism tended to be more highly expressed in patients with HCC than in patients without HCC. CONCLUSION: We identified genes that are associated with fibrosis progression and hepatocarcinogenesis. This information may be used to detect increased carcinogenic potential in the livers of patients with HCV infection.

Relevance network between chemosensitivity and transcriptome in human hepatoma cells.

Generally, hepatoma is not a chemosensitive tumor, and the mechanism of resistance to anticancer drugs is not fully elucidated. We aimed to comprehensively evaluate the relationship between chemosensitivity and gene expression profile in human hepatoma cells, by using microarray analysis, and analyze the data by constructing relevance networks. In eight hepatoma cell lines (HLE, HLF, Huh7, Hep3B, PLC/PRF/5, SK-Hep1, Huh6, and HepG2), the baseline expression levels of 2300 genes were measured by cDNA microarray. The concentrations of eight anticancer drugs (nimustine, mitomycin C, cisplatin, carboplatin, doxorubicin, epirubicin, mitoxantrone, and 5-fluorouracil) needed for 50% growth inhibition were examined and used as a measure of chemosensitivity. These data were combined and comprehensive pair-wise correlations between gene expression levels and the 50% growth inhibition values were calculated. Significant correlations with significance were used to construct networks of similarity. Fifty-two relations, including 42 genes, were selected. Among them, nearly 20% were various types of transporters, and most of them negatively correlated with chemosensitivity. Transporter associated with antigen processing 1 was associated with resistance to mitoxantrone, consistent with previous reports. Other transporters were not reported previously to associate with chemosensitivity. Resistance to doxorubicin and its analogue, epirubicin, were positively correlated with topoisomerase II beta expression, whereas it negatively correlated with expression of carboxypeptidases A3 and Z. Response to nimustine was associated with expression of superoxide dismutase 2. Relevance networks identified several negative correlations between gene expression and resistance, which were missed by hierarchical clustering. Our results suggested the necessity of systematically evaluating the transporting systems that may play a major role in resistance in hepatoma. This may provide useful information to modify anticancer drug action in hepatoma.

Identification of genes associated with sensitivity to 5-fluorouracil and cisplatin in hepatoma cells.

BACKGROUND: The prognosis of patients with advanced hepatoma is grim. Although chemotherapy is adapted to such patients, the efficacy is low and the outcome cannot be predicted before therapy. In this study, we aimed to identify genes associated with sensitivity to 5-fluorouracil and cisplatin, drugs widely used in treatment, using gene expression profiles. METHODS: Gene expression was evaluated in eight human hepatoma cell lines using an in-house cDNA microarray including 2300 known genes. The 50% growth inhibitory concentrations (GI50) of 5-fluorouracil and cisplatin were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and designated as chemosensitivity. Genes with expression ratios associated with GI50 were selected using the permutation test. RESULTS: For 5-fluorouracil and cisplatin, 21 and 40 genes, respectively, were selected. From among the genes associated with 5-fluorouracil and cisplatin, several encoding metabolic enzymes were selected. In addition, several genes involved in the cell cycle and transcription were identified. CONCLUSIONS: We identified genes that may be associated with sensitivity to 5-fluorouracil and cisplatin. A list of these genes may be useful to elucidate how these drugs work on human hepatoma.

Liver chip and gene shaving.

A comprehensive profile of genes expressed at the mRNA level in various human tissues is considered to be important for understanding the molecular mechanisms of the tissue-specific function and the pathogenesis of related diseases. Here, the gene expression profiling in three human digestive tissues, liver, stomach, and pancreas, was catalogued by generating a large number of expressed sequence tags, and clarified how quantitatively the gene expressions are different. After assembling the redundant clones among three tissues, the results showed that only 1.7% among the assembled genes was expressed commonly in the investigated tissues. These results suggest that the significant functional divergences in different tissues must be related to the divergence of the gene expression profiles. Recently, microarray technologies are widely used. Considering the results that different genes express in different tissues, however, it is important to spot the cDNAs derived from the same tissues or cells examined to acquire information efficiently. For the study of digestive diseases, we constructed an in-house microarray by using the cDNA sets derived from the digestive tissues (liver and gastric chip). In addition, because the amount of information acquired by the microarray analyses is huge, the power of bioinformatics for unifying the obtained data is indispensable. Some examples of the strategies for handling the microarray data obtained by our in-house microarrays are shown in this article.

A simple combination of serum type IV collagen and prothrombin time to diagnose cirrhosis in patients with chronic active hepatitis C.

BACKGROUND/AIM:: Cirrhosis in chronic hepatitis C is a major cause of mortality. The components of reported diagnostic indices of cirrhosis based on biochemical markers may be modified by therapies for hepatic inflammation. We aimed to construct index of cirrhosis in patients treated for chronic active hepatitis. METHODS:: Using sera of consecutive 140 patients with chronic hepatitis C, routine blood tests including fibrosis markers, type IV collagen and procollagen type III peptide (PIIIP), were performed. Diagnosis of cirrhosis was determined by biopsy. Using multivariate analyses, diagnostic indices of cirrhosis were constructed. RESULTS:: Fifty-eight patients were diagnosed to have cirrhosis. Platelet count, prothrombin time, and albumin were lower, and type IV collagen and PIIIP were higher in patients with cirrhosis (p<0.05). There was no difference in aspartate and alanine aminotransferases (AST, ALT) and gamma-glutamyl-transpeptidase (GGT) (p>0.3). Our diagnostic indices I (prothrombin time and platelet count) and II (prothrombin time and type IV collagen) of cirrhosis showed the area under the ROC curves (AUC) of 0.77 and 0.81, respectively. The index II was relatively superior to the index I. CONCLUSIONS:: Using combination of type IV collagen and prothrombin time, efficient diagnosis of cirrhosis can be performed in patients with chronic active hepatitis C.

Comparison of standard-dose and half­dose sorafenib therapy on clinical outcome in patients with unresectable hepatocellular carcinoma in field practice: A propensity score matching analysis.

The aims of the present study were to examine whether unresectable hepatocellular carcinoma (HCC) patients treated with initial dose of sorafenib of 400 mg/day (half-dose group) had comparable treatment efficacy, safety and survival merit as compared with those treated with initial dose of sorafenib of 800 mg/day (standard-dose group) in a multicenter large study. For reducing the bias in patient selection, we compared clinical outcomes of these two groups using propensity score matching analysis. A total of 465 patients were treated with sorafenib at fourteen hospitals in Japanese Red Cross Liver Study Group from 2008 to 2013. After propensity score matching, 139 matched HCC patients were selected for analysis in both groups. We retrospectively compared overall survival (OS), progression-free survival (PFS), best treatment response and sorafenib related serious adverse events (SAEs) in the two groups. There were no relevant differences in terms of OS (median OS intervals: 9.2 months in the standard-dose group and 9.7 months in the half­dose group, P=0.350), PFS (median PFS intervals: 3.4 months in the standard-dose group and 3.2 months in the half-dose group, P=0.729) and best treatment efficacy (objective response rate: P=0.416; disease control rate: P=0.719). Grade 3 or more SAEs were observed in 37 patients (26.6%) in the standard-dose group and 33 patients (23.7%) in the half-dose group (P=0.580). Furthermore, in all subgroup analyses according to Child-Pugh classification and Barcelona Clinic Liver Cancer stage, there were no significant differences in the two groups. In conclusion, unresectable HCC patients treated with initial half­dose sorafenib had comparable prognosis compared with those treated with initial standard-dose sorafenib.

Sorafenib Therapy for BCLC Stage B/C Hepatocellular Carcinoma; Clinical Outcome and Safety in Aged Patients: A Multicenter Study in Japan.

BACKGROUND AND AIMS: We aimed to compare clinical outcomes and safety after sorafenib therapy between patients with Barcelona Clinic Liver Cancer (BCLC) stage B or C hepatocellular carcinoma (HCC) aged ≥75 years (aged group, n=179) and those with BCLC stage B or C HCC aged <75 years (control group, n=279). PATIENTS AND METHODS: We compared overall survival (OS), progression free survival (PFS), best treatment response and sorafenib related serious adverse events (SAEs) of grade 3 or more in the two groups. Furthermore, for reducing the selection bias, we compared clinical outcome of these two groups using propensity score matching analysis. RESULTS: The median OS and PFS intervals were 9.7 and 3.8 months in the aged group and 8.2 and 3.3 months in the control group (P=0.641 for OS and P=0.068 for PFS). Disease control rates were 49.2% (88/179) in the aged group and 49.1% (137/279) in the control group (P>0.999). Objective response rates were 15.1% (27/179) in the aged group and 14.3% (40/279) in the control group (P=0.892). Treatment related SAEs of grade 3 or more were observed in 51 patients (28.5%) in the aged group and in 69 patients (24.7%) in the control group (P=0.385). In the propensity score matched cohort (132 pairs), no significant difference in the two groups was observed in terms of OS (P=0.898) and PFS (P=0.407). CONCLUSION: In BCLC stage B or C HCC patients treated with sorafenib, life expectancy, disease progression, treatment efficacy and SAEs are unaffected by age over 75 years.

Interferon-beta is activated by hepatitis C virus NS5B and inhibited by NS4A, NS4B, and NS5A.

Innate immunity is part of the antiviral response. Interferon (IFN)-beta plays a leading role in this system. To investigate the influence of hepatitis C virus (HCV) on innate immunity, we examined the effect of viral proteins on IFN-beta induction. HepG2 cells were co-transfected with plasmids for seven HCV proteins (core protein, NS2, NS3, NS4A, NS4B, NS5A, and NS5B) and the IFN-beta promoter luciferase. Toll-like receptor (TLR) 3 and Toll/IL-1 receptor domain-containing adapter inducing IFN-beta (TRIF) play key roles in dsRNA-mediated activation of interferon regulatory factor (IRF)-3 and IFN-beta; therefore, the participation of TLR3/TRIF in NS5B-mediated IFN induction was examined. Among seven HCV proteins, only NS5B, a viral RNA-dependent RNA polymerase (RdRp), activated the IFN-beta promoter. However, mutant NS5B without RdRp activity or template/primer association did not activate the IFN-beta promoter. Activation of the IFN-beta promoter by NS5B required the positive regulatory domain III, a binding sequence for IRF-3. Moreover, IRF-3 was phosphorylated by NS5B. Both inhibition of TLR3 expression by small interfering RNA and expression of the dominant negative form of TRIF significantly reduced NS5B-induced activation of IFN-beta. Of the six other HCV proteins, NS4A, NS4B, and NS5A efficiently inhibited this activation. HCV NS5B is a potent activator of the host innate immune system, possibly through TLR3/TRIF and synthesis of dsRNA. Meanwhile, NS4A, NS4B, and NS5A block IFN-beta induction by NS5B, which may contribute toward the persistence of this virus.

Hepatitis C virus core protein is a potent inhibitor of RNA silencing-based antiviral response.

BACKGROUND & AIMS: Persistent infection with hepatitis C virus (HCV) leads to chronic hepatitis and hepatocellular carcinoma (HCC). RNA interference (RNAi) may act as a host antiviral response against viral RNA. METHODS: The effects of RNAi on both the replicative intermediates and the internal ribosome entry site (IRES) of HCV were studied by using HCV-related short interfering RNA (siRNA) detection assay. The mechanism that permits HCV to escape RNAi was studied by using RNAi assay materials. RESULTS: These studies demonstrate that the Dicer, an RNase enzyme that generates short siRNA, can target and digest both the IRES and the replicative intermediate of HCV into siRNA of approximately 22 nucleotides. Further studies also show that Dicer can inhibit the replication of the HCV subgenomic replicon. However, the HCV core protein inhibits this RNAi and rescues the replication of the HCV subgenomic replicon through a direct interaction with Dicer. CONCLUSIONS: RNAi is a limiting factor for HCV infection, and the core protein suppresses the RNA silencing-based antiviral response. This ability of the core protein to counteract the host defense may lead to a persistent viral infection and may contribute to the pathogenesis of HCV.