The AMPK-related kinase SNARK regulates hepatitis C virus replication and pathogenesis through enhancement of TGF-β signaling

BACKGROUND & AIMS

Hepatitis C virus (HCV) is a major cause of chronic liver disease worldwide. The biological and therapeutic importance of host cellular cofactors for viral replication has been recently appreciated. Here we examined the roles of SNF1/AMP kinase-related kinase (SNARK) in HCV replication and pathogenesis.

METHODS

The JFH1 infection system and the full-length HCV replicon OR6 cell line were used. Gene expression was knocked down by siRNAs. SNARK mutants were created by site-directed mutagenesis. Intracellular mRNA levels were measured by qRT-PCR. Endogenous and overexpressed proteins were detected by Western blot analysis and immunofluorescence. Transforming growth factor (TGF)-β signaling was monitored by a luciferase reporter construct. Liver biopsy samples from HCV-infected patients were analyzed for SNARK expression.

RESULTS

Knockdown of SNARK impaired viral replication, which was rescued by wild type SNARK but not by unphosphorylated or kinase-deficient mutants. Knockdown and overexpression studies demonstrated that SNARK promoted TGF-β signaling in a manner dependent on both its phosphorylation and kinase activity. In turn, chronic HCV replication upregulated the expression of SNARK in patients. Further, the SNARK kinase inhibitor metformin suppressed both HCV replication and SNARK-mediated enhancement of TGF-β signaling.

CONCLUSIONS

Thus reciprocal regulation between HCV and SNARK promotes TGF-β signaling, a major driver of hepatic fibrogenesis. These findings suggest that SNARK will be an attractive target for the design of novel host-directed antiviral and antifibrotic drugs.

SOCS1 abrogates IFN's antiviral effect on hepatitis C virus replication

Suppressor of cytokine signaling 1 (SOCS1) and suppressor of cytokine signaling 3 (SOCS3) have been thought to block type I interferon (IFN) signaling. We have previously reported that SOCS3 suppresses HCV replication in an mTOR-dependent manner. However, the relationship between SOCS1 and HCV replication remains unclear. Here, we found that overexpression of SOCS1 alone did not have an effect on HCV RNA replication. However, suppression of HCV replication by IFN-α was rescued by SOCS1 overexpression. The upregulation of HCV replication by SOCS1 overexpression in the presence of IFN is likely a result of the impairment of IFN signaling by SOCS1 and subsequent induction of ISGs. Knockdown of SOCS1 alone with specific shRNA enhanced the antiviral effect of IFN compared with negative control. Thus, SOCS1 acts as a suppressor of type I IFN function against HCV.

ARF1 and GBF1 generate a PI4P-enriched environment supportive of hepatitis C virus replication

Cellular levels of phosphatidylinositol 4-phosphate (PI4P) have been shown to be upregulated during RNA replication of several viruses, including the HCV replicon model. However, whether PI4P is required in an infectious HCV model remains unknown. Moreover, it is not established whether the host transport machinery is sequestered by the generation of PI4P during HCV infection. Here we found that PI4P was enriched in HCV replication complexes when Huh7.5.1 cells were infected with JFH1. HCV replication was inhibited upon overexpression of the PI4P phosphatase Sac1. The PI4P kinase PI4KIIIβ was also found to be required for HCV replication. Moreover, the vesicular transport proteins ARF1 and GBF1 colocalized with PI4KIIIβ and were both required for HCV replication. During authentic HCV infection, PI4P plays an integral role in virus replication.

IL28B inhibits hepatitis C virus replication through the JAK-STAT pathway

BACKGROUND & AIMS

The combination of pegylated interferon (IFN) α and ribavirin (RBV) is the standard therapy for patients with chronic HCV infection. However, it produces a sustained virologic response (SVR) in only half of the treated individuals and is associated with significant side effects. Recently, several single-nucleotide polymorphisms (SNPs) near the IL28B locus, also known as IFNλ3, were identified to be strong predictors of SVR in patients receiving PEG-IFN and RBV. We sought to determine whether IL28B was capable of inhibiting HCV replication and to determine the pathway by which IL28B exhibits anti-HCV activity.

METHODS

Using the full-length HCV replicon OR6 and the infectious HCV clones JFH1 and Jc1, we assessed the anti-HCV effect of IL28B on HCV and characterized the key steps of the JAK-STAT pathway by real time PCR, luciferase assay, and Western blot. Finally, we evaluated the anti-HCV effect of IL28B in the presence of JAK-STAT pathway inhibitors such as blocking antibodies, a pharmacological inhibitor, and siRNAs.

RESULTS

We found that IL28B inhibits HCV replication in a dose- and time-dependent manner. Like IFNα, IL28B induces the phosphorylation of STAT1 and STAT2, ISRE-driven transcription, and expression of known ISGs. The anti-HCV effects of IL28A, IL28B, and IL29 were abrogated by an IL10R2 blocking antibody, a pharmacological inhibitor of JAK1/TYK2, and by siRNA against IL28R1, STAT1, STAT2, and IRF9.

CONCLUSIONS

Our data demonstrate that IL28A, IL28B, and IL29 signal through the JAK-STAT pathway to inhibit HCV. These data suggest possible applications of new approaches in HCV treatment.

HIV infection increases HCV-induced hepatocyte apoptosis

BACKGROUND & AIMS

HCV related liver disease is one of the most important complications in persons with HIV, with accelerated fibrosis progression in coinfected persons compared to those with HCV alone. We hypothesized that HCV-HIV coinfection increases HCV related hepatocyte apoptosis and that HCV and HIV influence TRAIL signaling in hepatocytes.

METHODS

We analyzed the effect of HIV in JFH1-infected Huh7.5.1 cells. Apoptosis was measured by Caspase-Glo 3/7 assay and Western blotting for cleaved PARP. TRAIL, TRAIL receptor 1 (DR4), and 2 (DR5) mRNA and protein levels were assessed by real-time PCR and Western blot, respectively. We also investigated activation of caspase pathways using caspase inhibitors and assessed expression of Bid and cytochrome C.

RESULTS

We found increased caspase 3/7 activity and cleaved PARP in JFH1 HCV-infected Huh7.5.1 cells in the presence of heat-inactivated HIV, compared to Huh7.5.1 cells infected with JFH1 or exposed to heat-inactivated HIV alone. Both DR4 and DR5 mRNA and protein expression were increased in JFH1-infected cells in the presence of inactivated HIV compared to Huh7.5.1 cells infected with JFH1 or exposed to heat-inactivated HIV alone. Pancaspase, caspase-8, and caspase-9 inhibition blocked apoptosis induced by HCV, inactivated HIV, and HCV plus inactivated HIV. A caspase-9 inhibitor blocked apoptosis induced by HCV, HIV, and HCV-HIV comparably to pancaspase and caspase-8 inhibitors. HCV induced the activation of Bid cleavage and cytochrome C release. The addition of HIV substantially augmented this induction.

CONCLUSIONS

Our findings indicate that hepatocyte apoptosis is increased in the presence of HCV and HIV compared to HCV or HIV alone, and that this increase is mediated by DR4 and DR5 up-regulation. These results provide an additional mechanism for the accelerated liver disease progression observed in HCV-HIV co-infection.

Hepatitis B screening, prophylaxis and re-activation in the era of rituximab-based chemotherapy

BACKGROUND

Hepatitis B re-activation is a well-described complication in patients with inactive chronic hepatitis B receiving chemotherapy. Screening for HBV and pre-emptive therapy are recommended. However, the rates of HBV screening, prophylaxis and re-activation during rituximab-containing chemotherapy are unknown.

PATIENTS AND METHODS

We performed a retrospective study of patients with non-Hodgkin lymphoma (NHL) who received rituximab between August 1997 and September 2009. We evaluated patients for hepatitis B serologies, antiviral prophylaxis and hepatitis B re-activation during or up to 6 months after chemotherapy.

RESULTS

One thousand four hundred and twenty-nine patients underwent rituximab-containing chemotherapy for NHL. Hepatitis B serologies were documented in 524 (36.6%) patients. Of these, 20 (3.8%) were HBsAg positive and 10 (50%) experienced HBV re-activation. Only half (5/10) had HBV serology documented before re-activation. Only 3/8 (37.5%) of patients with newly documented HBsAg positivity received antiviral prophylaxis. Virological breakthrough occurred in two of the patients on chronic therapy, in one of three inactive carriers on prophylaxis and in two of five patients not receiving prophylaxis. Re-activation developed in another five patients not screened previously for hepatitis B. One patient developed ALF and died. Re-activation did not occur in 25 patients with isolated positive core antibody.

CONCLUSIONS

At tertiary care institutions hepatitis B serologies are infrequently assessed before rituximab-based chemotherapy and prophylaxis is uncommon. Greater adherence to recommendations for screening and prophylaxis is necessary. This suboptimal screening rate could be even lower in community hospitals and could result in significant harm to unscreened and unprophylaxed patients.

Hepatitis C virus regulates transforming growth factor beta1 production through the generation of reactive oxygen species in a nuclear factor kappaB-dependent manner

BACKGROUND & AIMS

The generation of oxidative stress and transforming growth factor beta1 (TGF-beta1) production play important roles in liver fibrogenesis. We have previously shown that hepatitis C virus (HCV) increases hepatocyte TGF-beta1 expression. However, the mechanisms by which this induction occurs have not been well studied. We explored the possibility that HCV infection regulates TGF-beta1 expression through the generation of reactive oxygen species (ROS), which act through > or =1 of the p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and nuclear factor kappaB (NFkappaB) signaling pathways to induce TGF-beta1 expression.

METHODS

We used small molecule inhibitors and short interfering RNAs to knock down these pathways to study the mechanism by which HCV regulates TGF-beta1 production in the infectious JFH1 model.

RESULTS

We demonstrated that HCV induces ROS and TGF-beta1 expression. We further found that JFH1 induces the phosphorylation of p38MAPK, JNK, ERK, and NFkappaB. We also found that HCV-mediated TGF-beta1 enhancement occurs through a ROS-induced and p38 MAPK, JNK, ERK1/2, NFkappaB-dependent pathway.

CONCLUSIONS

These findings provide further evidence to support the hypothesis that HCV enhances hepatic fibrosis progression through the generation of ROS and induction of TGF-beta1. Strategies to limit the viral induction of oxidative stress appear to be warranted to inhibit fibrogenesis.

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.

Hepatic SOCS3 expression is strongly associated with non-response to therapy and race in HCV and HCV/HIV infection

BACKGROUND/AIMS

The response rates of HCV infection to interferon therapy vary depending on viral and host factors. We hypothesized that key regulators of the IFN signaling pathway are predictive of treatment outcome.

METHODS

We measured the expression of signal transducer and activator of transcription 1 (STAT1) and suppressor of cytokine signaling 3 (SOCS3) in pretreatment liver biopsies. Staining quantitation was compared to treatment outcomes.

RESULTS

Forty-nine patients with HCV and 25 patients with HCV/HIV infection treated with peginterferon/ribavirin were analyzed. Pretreatment hepatic SOCS3 expression was higher in non-responders than responders. Genotype 1 responders had similar levels of SOCS3 as genotype 2/3 responders. African Americans (AA) had higher hepatic SOCS3 than non-AA. Pretreatment hepatic SOCS3 was the most powerful independent predictor of sustained virologic response (SVR), even more so than genotype by logistic regression analysis. Failure to achieve SVR and AA race were independently associated with high hepatic SOCS3 levels. The hepatic expression of STAT-1 did not differ between responders and non-responders.

CONCLUSIONS

Our data indicate that hepatic SOCS3 is a stronger baseline predictor of antiviral response than viral genotype. Poor response to antiviral therapy in AA may be associated with higher hepatic SOCS3 expression.

Association of interferon regulatory factor-7 gene polymorphism with liver cirrhosis in chronic hepatitis C patients

BACKGROUND AND AIMS

Interferon (IFN) regulatory factor 7 (IRF-7) has been shown to play an essential role in the transcriptional activation of virus-inducible cellular genes, especially IFN genes. Polymorphisms of the IRF-7 gene may probably affect both the quality and the quantity of IRF-7. We investigated the role of IRF-7 polymorphisms in Japanese patients with chronic hepatitis C virus (HCV) infection.

METHODS

We studied a total of nine polymorphisms of the IRF-7 gene including SNP1047A/G (Lys/Glu) and SNP2157A/G (Gln/Arg) using the Taqman allelic discrimination and sequencing techniques in 406 Japanese patients with chronic HCV infection. We further performed functional analysis of SNP1047 and SNP2157 by transcriptional activation of the IFNA promoter.

RESULTS

We found that SNP1047AG and SNP2157AG genotypes were in complete linkage disequilibrium and were present in a significantly higher proportion in HCV-infected patients with cirrhosis (5.6%) than in those without cirrhosis (1.7%) (P=0.03). Multivariate analysis also revealed that SNP1047 and SNP2157 were independently associated with cirrhosis at an odds ratio of 2.5. Functional analysis revealed that SNP1047G and SNP2157G alleles increased IFNA expression.

CONCLUSION

SNP1047AG and SNP2157AG genotypes were strongly associated with cirrhosis. SNP1047G and SNP2157G alleles might be used as markers of host factors associated with a higher risk of cirrhosis in Japanese patients with chronic HCV infection.

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

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.

HIV increases HCV replication in a TGF-beta1-dependent manner

BACKGROUND & AIMS

Human immunodeficiency virus (HIV) coinfection increases hepatitis C virus (HCV)-related progression of hepatic fibrosis, increases HCV persistence, and decreases response rates to interferon-based anti-HCV therapy. It has remained unclear how HIV, a nonhepatotropic virus, accelerates the progression of liver disease by HCV.

METHODS

We explored the possibility that circulating HIV and/or its proteins contribute to the pathogenesis of HCV through engagement of extracellular coreceptors on hepatocytes.

RESULTS

In this study, we found that inactivated HIV or gp120 increases HCV replication and enhances HCV-regulated transforming growth factor (TGF)-beta1 expression in both a replicon and an infectious model of HCV. This proviral effect of HIV and gp120 on HCV replication is neutralized by antibodies to CCR5 or CXCR4. However, HIV and gp120 did not alter type I interferon-mediated signaling in these HCV models, indicating that HIV regulates HCV replication through an alternative mechanism. Interestingly, we found that human TGF-beta1 also enhanced HCV replication. The effect of HIV on HCV replication was blocked by a neutralizing antibody to TGF-beta1, indicating that its effects on HCV replication are TGF-beta1 dependent.

CONCLUSIONS

These results suggest a novel mechanism by which HIV not only enhances HCV replication but also contributes to progression of hepatic fibrosis.

MDM2 promoter SNP309 is associated with the risk of hepatocellular carcinoma in patients with chronic hepatitis C

PURPOSE

A single nucleotide polymorphism (SNP) in the promoter region of MDM2 gene, SNP309, has recently been shown to be associated with accelerated tumor formation in both hereditary and sporadic cancers in humans. However, the association of SNP309 with hepatocellular carcinoma is unknown. We evaluated the association of SNP309 with the risk of hepatocellular carcinoma development among Japanese patients with chronic hepatitis C virus infection.

EXPERIMENTAL DESIGN

We genotyped the SNP309 at the MDM2 promoter in 435 Japanese patients with chronic hepatitis C virus infection, including 187 patients with hepatocellular carcinoma and 48 healthy subjects, using a fluorogenic PCR. Presence of SNP was also confirmed by direct sequencing of the MDM2 promoter region.

RESULTS

The proportion of G/G genotype of the SNP309 in patients with hepatocellular carcinoma (33%) was significantly higher than that in patients without hepatocellular carcinoma (23%), with an odds ratio (95% confidence interval) of 2.28 (1.30-3.98). A multivariate analysis revealed that MDM2 SNP309 (G/G versus T/T), age >60 years, male gender, presence of cirrhosis, serum alpha-fetoprotein >20 mug/L, and serum albumin <3.2 g/dL were independently associated with the hepatocellular carcinoma development at odds ratio of 2.27, 2.46, 3.08, 4.15, 4.87, and 6.33, respectively.

CONCLUSIONS

The MDM2 promoter SNP309 is associated with the presence of hepatocellular carcinoma in Japanese patients with chronic hepatitis C.

Nucleotide change of codon 38 in the X gene of hepatitis B virus genotype C is associated with an increased risk of hepatocellular carcinoma

BACKGROUND/AIMS

The hepatitis B virus (HBV) genotype C is associated with the development of hepatocellular carcinoma (HCC). In addition, the HBV X gene, which encodes the pleiotropic transactivator HBx, has also been associated with the development of HCC. In this study, we investigated whether nucleotide changes in the X gene of genotype C are associated with the development of HCC.

METHODS/RESULTS

We sequenced the X gene in age- and sex-matched 39 HBV-infected patients with HCC and 36 HBV-infected patients without HCC. A novel nucleotide change that resulted in a proline to serine substitution at codon 38 in HBx (codon-38 change) was preferentially found in patients with HCC. Then, sera were collected from a new group of age- and sex-matched 52 patients with HCC and 51 patients without HCC. In this cohort also, the codon-38 change was associated with HCC. Multiple logistic regression analysis showed the prevalence of the codon-38 change was significantly associated with HCC in all patients (P=0.001, odds ratio: 4.89).

CONCLUSION

The codon-38 change in genotype C is an independent risk factor for the development of HCC and may serve as a useful molecular marker for predicting the clinical outcomes in patients infected with HBV.

Large-scale search of single nucleotide polymorphisms for hepatocellular carcinoma susceptibility genes in patients with hepatitis C

Hepatitis C virus (HCV) infection is a major risk factor for developing hepatocellular carcinoma (HCC). The host genetic factors that are involved in the development of HCC in patients with HCV infection remain to be investigated. To search for single nucleotide polymorphisms (SNPs) in HCC susceptibility genes, 393 SNPs in 171 candidate genes were examined in 188 Japanese patients with chronic HCV infection, including 77 patients with HCC. HCC-related SNPs were then examined in another 188 patients (including 93 patients with HCC) with chronic HCV infection. Haplotype analyses of HCC-related genes were performed in a total of 376 patients. Of the 393 SNPs, 31 SNPs in 29 genes were significantly associated with HCC based on an initial screening (P < .05). Of these 31 SNPs, 3 SNPs of 3 genes (SCYB14, GFRA1, and CRHR2) were significantly associated with HCC in a secondary screening. Haplotype analyses of these 3 genes identified 2 haplotype blocks associated with HCC. In conclusion, these SNPs and haplotypes located in the SCBY14, CRHR2, and GFRA1 genes will be used as markers to identify a subgroup of Japanese patients with chronic HCV infection who are at high risk of developing HCC.

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.

Vitamin K2 binds 17β-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.

Acyclic retinoid inhibits human hepatoma cell growth by suppressing fibroblast growth factor-mediated signaling pathways

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is one of the most common human malignancies. Its high mortality rate is mainly a result of high intrahepatic recurrence. The novel synthetic retinoid acyclic retinoid (ACR) has been reported to prevent the recurrence of human HCC after surgical resection of primary tumors, but the molecular mechanisms underlying its effects remain to be elucidated. In this study, we clarified the molecular targets of ACR.

METHODS

The inhibitory effects by ACR on growth were examined. Intracellular signaling induced by ACR was comprehensively studied by a reporter assay. Gene expression changes by ACR were examined using a microarray. From these results, a candidate signaling pathway modulated by ACR was determined and whether antagonizing this pathway reverses the effect was examined.

RESULTS

We show that ACR inhibits the growth of HCC cells through the down-regulation of fibroblast growth factor (FGF) receptor 3 expression and FGF-mediated signaling, which in turn suppresses the activity of Rho and serum response factor-mediated transcription. Conversely, overexpression of the active form of FGF receptor 3 or the addition of FGF reverses the ACR-mediated inhibition of growth. In addition, silencing the FGF receptor 3 gene by RNA interference inhibits cell growth.

CONCLUSIONS

These studies show that ACR is a potent inhibitor of FGF signaling and that selective blocking of the FGF-mediated pathway could be a promising therapeutic approach for the management of patients with HCC.

Vitamin K2 inhibits the growth and invasiveness of hepatocellular carcinoma cells via protein kinase A activation

Hepatocellular carcinoma (HCC) is a common human malignancy. Its high mortality rate is mainly a result of high intrahepatic recurrence and portal venous invasion (PVI). We previously reported that the development of PVI is related to levels of des-gamma-carboxy prothrombin (DCP), a serum protein that increases at a notably higher rate in patients with HCC. Because DCP is produced by a vitamin K shortage, we examined the biological effects of extrinsic supplementation of vitamin K(2) in HCC cells in vitro and in vivo. Consequently, vitamin K(2) inhibits the growth and invasion of HCC cells through the activation of protein kinase A, which modulates the activities of several transcriptional factors and inhibits the small GTPase Rho, independent of suppression of DCP. In addition, administration of vitamin K(2) to nude mice inoculated with liver tumor cells reduced both tumor growth and body weight loss. In conclusion, similar to an acyclic retinoid--which was previously reported to prevent the recurrence of HCC--vitamin K(2), another lipid-soluble vitamin, may be a promising therapeutic means for the management of HCC.