Hepatocyte-Specific Yap1 Knockout Maintained the Liver Homeostasis of Lipid Metabolism in Mice.

Introduction: Yes-associated protein 1 (YAP1) is a crucial molecule in the Hippo pathway. The impact of hepatocyte-specific Yap1 knockout (Yap1 LKO) on hepatic lipid droplets (LD) and pePLIN2 in metabolic fatty liver has not been reported. This study aims to explore whether Yap1 LKO could offer a protective effect in a liver injury model. Methods: Three-week-old Yap1 LKO and Yap1 Flox mice were given aristolochic acid I (AAI) combined carbon tetrachloride (CCL4) establish liver injury model. Eight-week-old Yap1 LKO and Yap1 Flox mice were fed with a high-fat diet for 18 weeks to establish obesity-related liver injury model. Further biochemical, histomorphological, immunohistochemical, and lipidomic analyses were performed on serum and liver tissues of these mice to elucidate the effects of hepatocyte-specific Yap1 knockout on hepatic lipid metabolism. Results: Yap1 LKO reduced triglyceride (TG) content and PLIN2 expression level in the liver during the intervention of AAI combined CCl4. Moreover, Yap1 LKO improved lipid metabolism homeostasis in the liver by increasing the beneficial lipid molecules and reducing the harmful lipid molecules through lipidomics. Finally, Yap1 LKO reduced TG content in the serum and liver, hepatic vacuolar degeneration, and hepatic PLIN2 expression level in mice fed with a high-fat diet (HFD). Conclusion: Yap1 LKO is protective in regulating liver and blood TG when induced with toxic substances AAI combined CCl4 and a high-fat diet.

Dihydroartemisinin increased the abundance of Akkermansia muciniphila by YAP1 depression that sensitizes hepatocellular carcinoma to anti-PD-1 immunotherapy.

The effect of anti-programmed cell death 1 (anti-PD-1) immunotherapy is limited in patients with hepatocellular carcinoma (HCC). Yes-associated protein 1 (YAP1) expression increased in liver tumor cells in early HCC, and Akkermansia muciniphila abundance decreased in the colon. The response to anti-PD-1 treatment is associated with A. muciniphila abundance in many tumors. However, the interaction between A. muciniphila abundance and YAP1 expression remains unclear in HCC. Here, anti-PD-1 treatment decreased A. muciniphila abundance in the colon, but increased YAP1 expression in the tumor cells by mice with liver tumors in situ. Mechanistically, hepatocyte-specific Yap1 knockout (Yap1LKO) maintained bile acid homeostasis in the liver, resulting in an increased abundance of A. muciniphila in the colon. Yap1 knockout enhanced anti-PD-1 efficacy. Therefore, YAP1 inhibition is a potential target for increasing A. muciniphila abundance to promote anti-PD-1 efficacy in liver tumors. Dihydroartemisinin (DHA), acting as YAP1 inhibitor, increased A. muciniphila abundance to sensitize anti-PD-1 therapy. A. muciniphila by gavage increased the number and activation of CD8+ T cells in liver tumor niches during DHA treatment or combination with anti-PD-1. Our findings suggested that the combination anti-PD-1 with DHA is an effective strategy for liver tumor treatment.

Si-Ni-San reduces lipid droplet deposition associated with decreased YAP1 in metabolic dysfunction-associated fatty liver disease.

ETHNOPHARMACOLOGICAL RELEVANCE: Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common chronic liver disease worldwide. However, its complex pathogenesis and lack of effective drugs for treating it present significant challenges. Si-Ni-San (SNS) is one of the representative formulas for treating patients with MAFLD in traditional Chinese medicine (TCM) clinics. According to our previous work, SNS reduces lipid droplet (LD) deposition in livers of mice with MAFLD. AIM OF THE STUDY: To elucidate the mechanism of SNS in reducing LD deposition in MAFLD. MATERIALS AND METHODS: First, LD areas were detected with Oil red O staining in HepG2 cells induced by oleic acid (OA). Cell Counting Kit-8 (CCK-8) assay was used to test cell viability after treatment with different concentrations of SNS serum. The expression of Yes-associated protein 1 (YAP1) was monitored by Western blot. Second, C57BL/6 mice were fed a high-fat diet (HFD) for 12 weeks and gavaged with SNS decoction during the 11th and 12th weeks. Then, the weight of the body and the liver was examined. LD numbers and their locations in the liver were detected by triglyceride (TG) assay and hematoxylin and eosin staining (H&E). The expression levels of YAP1 and perilipin2 (PLIN2) were detected using Western blot and immunohistochemistry (IHC) in liver tissues. Finally, active ingredients of SNS decoction and SNS serum were identified by liquid chromatography-mass spectrometry (LC-MS). Finally, molecular docking was performed between the compounds in SNS and YAP1 to analyze their active interaction. RESULTS: Cellular experiments showed that SNS serum reduced LD vacuoles and YAP1 expression in OA-induced HepG2 cells. Animal experiments confirmed that LD vacuoles, PLIN2 expression (3.16-fold), and YAP1 expression (2.50-fold) were increased in the HFD group compared with the normal diet (ND) group. SNS reduced LD vacuoles, TG content (0.84-fold), PLIN2 expression (0.33-fold), and YAP1 expression (0.27-fold) compared with the normal saline (NS) group in Yap1Flox mice with MAFLD. In SNS, baicalein-6-glucuronide, desoxylimonin, galangin-7-glucoside, glycyrrhizic-acid, licoricesaponin-K2, and nobiletin showed a high binding effect with YAP1. Knockout of hepatocyte YAP1 reduced LD vacuoles, TG content (0.40-fold), and PLIN2 expression (0.62-fold) in mice. Meanwhile, SNS reduced LD vacuoles, TG content (0.70-fold), and PLIN2 expression (0.19-fold) in Yap1LKO mice with MAFLD. The effect of SNS in reducing TG and PLIN2 was diminished in Yap1LKO mice compared with Yap1Flox mice. CONCLUSION: SNS reduced LD deposition and YAP1 expression in MAFLD liver cells both in vivo and in vitro. YAP1 was highly expressed in livers with MAFLD, and knockout of hepatocellular YAP1 reduced LD deposition in mice. SNS reduced LD deposition associated with decreased YAP1 in MAFLD liver cells.

Wolfberry enhanced the abundance of Akkermansia muciniphila by YAP1 in mice with acetaminophen-induced liver injury.

Drug-induced liver injury (DILI) by acetaminophen (APAP) was one of the most challenging liver diseases. Wolfberry (Lycium barbarum L.), a traditional Chinese medicinal material and food supplement, has a potential effect on increasing the abundance of Akkermansia muciniphila (A. muciniphila) in mice colons. However, the effect and mechanism of wolfberry remain unclear in APAP-induced DILI. In this study, wolfberry promoted the proliferation of activated-A. muciniphila in vitro and in vivo. For the first time, we detected that the activated-A. muciniphila but not the killed-A. muciniphila increased the expression level of Yes-associated protein 1 (YAP1) in the liver and alleviated liver injury in APAP-induced DILI mice. Mechanically, A. muciniphila improved the intestinal mucosal barrier and reduced lipopolysaccharide (LPS) content in the liver, leading to the increased expression level of YAP1. Furthermore, wolfberry increased the A. muciniphila abundance in the colon and YAP1 expression in the liver from APAP-induced DILI mice, which promoted the recovery of APAP-induced liver injury. Meanwhile, wolfberry combination with A. muciniphila synergistically increased AKK abundance and YAP1 expression in the liver. Our research provides an innovative strategy to improve DILI.

Dihydroartemisinin inhibited the Warburg effect through YAP1/SLC2A1 pathway in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) was the third most common cause of cancer death. But it has only limited therapeutic options, aggressive nature, and very low overall survival. Dihydroartemisinin (DHA), an anti-malarial drug approved by the Food and Drug Administration (FDA), inhibited cell growth in HCC. The Warburg effect was one of the ten new hallmarks of cancer. Solute carrier family 2 member 1 (SLC2A1) was a crucial carrier for glucose to enter target cells in the Warburg effect. Yes-associated transcriptional regulator 1 (YAP1), an effector molecule of the hippo pathway, played a crucial role in promoting the development of HCC. This study sought to determine the role of DHA in the SLC2A1 mediated Warburg effect in HCC. In this study, DHA inhibited the Warburg effect and SLC2A1 in HepG2215 cells and mice with liver tumors in situ. Meanwhile, DHA inhibited YAP1 expression by inhibiting YAP1 promoter binding protein GA binding protein transcription factor subunit beta 1 (GABPB1) and cAMP responsive element binding protein 1 (CREB1). Further, YAP1 knockdown/knockout reduced the Warburg effect and SLC2A1 expression by shYAP1-HepG2215 cells and Yap1LKO mice with liver tumors. Taken together, our data indicated that YAP1 knockdown/knockout reduced the SLC2A1 mediated Warburg effect by shYAP1-HepG2215 cells and Yap1LKO mice with liver tumors induced by DEN/TCPOBOP. DHA, as a potential YAP1 inhibitor, suppressed the SLC2A1 mediated Warburg effect in HCC.

Dihydroartemisinin broke the tumor immunosuppressive microenvironment by inhibiting YAP1 expression to enhance anti-PD-1 efficacy.

The efficacy of anti-PD-1 therapy is not as expected in hepatocellular carcinoma (HCC). YAP1 was overexpressed and activated in HCC. The mechanism of YAP1 in HCC immune escape is unclear. Anti-PD-1 treatment increased YAP1 expression in liver tumor cells, and exhausted CD4+ and CD8+ T cells in the blood and spleen of liver tumor mice. YAP1 knockdown suppressed PD-L1 expression, which was involved in JAK1/STAT1, 3 pathways. Moreover, Yap1 knockout elevated CD4+ and CD8+ T cells in liver tumor niche. Consistently, verteporfin, YAP1 inhibitor, decreased TGF-ß and IFN-γ in liver tumor niche and exhausted CD8+ T cell in the spleen. DHA suppressed YAP1 expression and break immune evasion in liver tumor niche, characterized by decreased PD-L1 in liver tumor cells and increased CD8+ T cell infiltration. Furthermore, DHA combined with anti-PD-1 treatment promoted CD4+ T cell infiltration in the spleen and CD8+ T cell in tumor tissues of mice. In summary, YAP1 knockdown in liver tumor cells suppressed PD-L1 expression and recruited cytotoxic T lymphocytes (CTLs), leading to break immune evasion in tumor niche. Mechanistically, YAP1 knockdown suppressed PD-L1 expression, which was involved in JAK1/STAT1, 3 pathways. Finally, DHA inhibited YAP1 expression, which not only inhibited liver tumor proliferation but also break the immunosuppressive niche in liver tumor tissues and improve the effect of anti-PD-1 therapy.

The Effects of Qinghao-Kushen and Its Active Compounds on the Biological Characteristics of Liver Cancer Cells.

Background and Aims: Artemisia annua (Qinghao) and Sophora flavescens (Kushen) are traditional Chinese medicines (TCMs). They are widely used in disease therapy, including hepatocellular carcinoma (HCC). However, their key compounds and targets for HCC treatment are unclear. This article mainly analyzed the vital active compounds and the mechanism of Qinghao-Kushen acting on HCC. Methods: First, we chose a traditional Chinese medicine, which has an excellent clinical effect on HCC by network meta-analysis. Then, we composed the Qinghao-Kushen herb pair and prepared the medicated serum. The active compounds of Qinghao-Kushen were verified by the LC-MS method. Next, we detected key targets from PubChem, SymMap, SwissTargetPrediction, DisGeNET, and GeneCards databases. Subsequently, the mechanism of Qinghao-Kushen was predicted by network pharmacology strategy and primarily examined in HuH-7 cells, HepG2 cells, and HepG2215 cells. Results: The effect of the Qinghao-Kushen combination was significantly better than that of single Qinghao or single Kushen in HepG2 and HuH-7 cells. Qinghao-Kushen increased the expression of activated caspase-3 protein than Qinghao or Kushen alone in HepG2 and HepG2215 cells. Network analyses and the LC-MS method revealed that the pivotal compounds of Qinghao-Kushen were matrine and scopoletin. GSK-3ß was one of the critical molecules related to Qinghao-Kushen. We confirmed that Qinghao-Kushen and matrine-scopoletin decreased the expression of GSK-3ß in HepG2 cells while increased GSK-3ß expression in HepG2215 cells. Conclusions: This work not only illustrated that the practical components of Qinghao-Kushen on HCC were matrine and scopoletin but shed light on the inhibitory of Qinghao-Kushen and matrine-scopoletin on liver cancer cells. Moreover, Qinghao-Kushen and matrine-scopoletin had a synergistic effect over the drug alone in HuH-7, HepG2, or HepG2215 cells. GSK-3ß may be a potential target for HCC therapy.

Solute carrier family 2 members 1 and 2 as prognostic biomarkers in hepatocellular carcinoma associated with immune infiltration.

BACKGROUND: Metabolic reprogramming has been identified as a core hallmark of cancer. Solute carrier family 2 is a major glucose carrier family. It consists of 14 members, and we mainly study solute carrier family 2 member 1 (SLC2A1) and solute carrier family 2 member 2 (SLC2A2) here. SLC2A1, mainly existing in human erythrocytes, brain endothelial cells, and normal placenta, was found to be increased in hepatocellular carcinoma (HCC), while SLC2A2, the major transporter of the normal liver, was decreased in HCC. AIM: To identify if SLC2A1 and SLC2A2 were associated with immune infiltration in addition to participating in the metabolic reprogramming in HCC. METHODS: The expression levels of SLC2A1 and SLC2A2 were tested in HepG2 cells, HepG215 cells, and multiple databases. The clinical characteristics and survival data of SLC2A1 and SLC2A2 were examined by multiple databases. The correlation between SLC2A1 and SLC2A2 was analyzed by multiple databases. The functions and pathways in which SLC2A1, SLC2A2, and frequently altered neighbor genes were involved were discussed in String. Immune infiltration levels and immune marker genes associated with SLC2A1 and SLC2A2 were discussed from multiple databases. RESULTS: The expression level of SLC2A1 was up-regulated, but the expression level of SLC2A2 was down-regulated in HepG2 cells, HepG215 cells, and liver cancer patients. The expression levels of SLC2A1 and SLC2A2 were related to tumor volume, grade, and stage in HCC. Interestingly, the expression levels of SLC2A1 and SLC2A2 were negatively correlated. Further, high SLC2A1 expression and low SLC2A2 expression were linked to poor overall survival and relapse-free survival. SLC2A1, SLC2A2, and frequently altered neighbor genes played a major role in the occurrence and development of tumors. Notably, SLC2A1 was positively correlated with tumor immune infiltration, while SLC2A2 was negatively correlated with tumor immune infiltration. Particularly, SLC2A2 methylation was positively correlated with lymphocytes. CONCLUSION: SLC2A1 and SLC2A2 are independent therapeutic targets for HCC, and they are quintessential marker molecules for predicting and regulating the number and status of immune cells in HCC.

Dihydroartemisinin promoted FXR expression independent of YAP1 in hepatocellular carcinoma.

Loss of FXR, one of bile acid receptors, enlarged livers. Yes-associated protein 1 (YAP1), a dominant oncogene, promotes hepatocellular carcinoma (HCC). However, the relationship between FXR and YAP1 was unspecified in bile acid homeostasis in HCC. Here, we used TIMER2.0, the Cancer Genome Atlas (TCGA) Database, and Kaplan-Meier Plotter Database and discovered that FXR was positively correlated with better prognosis in liver cancer patients. Our previous research showed that dihydroartemisinin (DHA) inhibited cell proliferation in HepG2 and HepG22215 cells. However, the relationship of YAP1 and the bile acid receptor FXR remains elusive during DHA treatment. Furthermore, we showed that DHA improved FXR and reduced YAP1 in the liver cancer cells and mice. Additionally, the expression of nucleus protein FXR was enhanced in Yap1LKO mice with liver cancer. DHA promoted the expression level of whole and nuclear protein FXR independent of YAP1 in Yap1LKO mice with liver cancer. DHA declined cholesterol 7α-hydroxylase, but not sterol 27-hydroxylase, and depressed cholic acid and chenodeoxycholic acid of liver tissue in Yap1LKO mice with liver cancer. Generally, our results suggested that DHA improved FXR and declined YAP1 to suppress bile acid metabolism. Thus, we suggested that FXR acted as a potential therapeutic target in HCC.

Modulation of Oral Microflora during Helicobacter Pylori Eradication.

OBJECTIVE: To analyse the saliva microbial abundance and composition by 16s rRNA sequence during Helicobacter pylori (H.pylori) eradication. STUDY DESIGN: Descriptive study. PLACE AND DURATION OF STUDY: Hebei University of Chinese Medicine, Hebei Provincial Hospital of Traditional Chinese Medicine, from March 2019 to January 2020. METHODOLOGY: The saliva microbial were analysed before and after the bismuth-containing quadruple therapy. A total of ten saliva samples (three groups) were enrolled in the study. The authors used the linear discriminant analysis effect size (LEfSe) method and Welch's t-test for comparative analysis to identify which taxa could be significantly affected in three groups. RESULTS: H.pylori 16S rRNA gene sequence was not detected in the ten saliva samples. The abundance of Prevotella_sp._oral_clone_P4PB_83_P2 from healthy adults was higher than H.pylori-positive patients. Moreover, after the bismuth-containing quadruple therapy, the diversity and richness of saliva bacteria reduced. Lautropia, Burkholderiales, uncultured bacterium, Burkholderiaceae, and Actinomyces were enriched in H.pylori-positive patient samples after the bismuth-containing quadruple therapy. CONCLUSION: The diversity and richness of salivary microbiome were reduced in H.pylori-positive patient, and bismuth-containing quadruple therapy affected oral microbiota. Key Words: Helicobacter pylori, Saliva, Microbiota, RNA, Bismuth.

Dihydroartemisinin reduced lipid droplet deposition by YAP1 to promote the anti-PD-1 effect in hepatocellular carcinoma.

BACKGROUND: Anti-PD-1 was used to treat for many cancers, but the overall response rate of monoclonal antibodies blocking the inhibitory PD-1/PD-L1 was less than 20%. Lipid droplet (LD) deposition reduced chemotherapy efficacy, but whether LD deposition affects anti-PD-1 treatment and its mechanism remains unclear. Dihydroartemisinin (DHA) was FDA proved antimalarial medicine, but its working mechanism on LD deposition has not been clarified. PURPOSE: This study aimed to elucidate the mechanism of DHA reducing LDs deposition and improving the efficacy of anti-PD-1. METHODS: LD numbers and area were separately detected by electron microscopy and oil Red O staining. The expression of YAP1 and PLIN2 was detected by immunohistochemical staining in liver cancer tissues. Transcription and protein expression levels of YAP1 and PLIN2 in cells were detected by qRT-PCR and Western blot after DHA treated HepG2215 cells and Yap1LKO mice. RESULTS: LD accumulation was found in the liver tumor cells of DEN/TOPBCOP-induced liver tumor mice with anti-PD-1 treatment. But DHA treatment or YAP1 knockdown reduced LD deposition and PLIN2 expression in HepG2215 cells. Furthermore, DHA reduced the LD deposition, PLIN2 expression and triglycerides (TG) content in the liver tumor cells of Yap1LKO mice with liver tumor. CONCLUSION: Anti-PD-1 promoted LD deposition, while YAP1 knockdown/out reduced LD deposition in HCC. DHA reduced LD deposition by inhibiting YAP1, enhancing the effect of anti-PD-1 therapy.

Anti-malarial drug dihydroartemisinin downregulates the expression levels of CDK1 and CCNB1 in liver cancer.

Liver cancer is the third leading cause of cancer-associated mortality worldwide. By the time liver cancer is diagnosed, it is already in the advanced stage. Therefore, novel therapeutic strategies need to be identified to improve the prognosis of patients with liver cancer. In the present study, the profiles of GSE84402, GSE19665 and GSE121248 were used to screen differentially expressed genes (DEGs). Subsequently, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses for DEGs were conducted using the Database for Annotation, Visualization and Integrated Discovery. The protein-protein interaction network was established to screen the hub genes associated with liver cancer. Additionally, the expression levels of hub genes were validated using the Gene Expression Profiling Interactive Analysis and Oncomine databases. In addition, the prognostic value of hub genes in patients with liver cancer was analyzed using Kaplan-Meier Plotter. It was demonstrated that 132 and 246 genes were upregulated and downregulated, respectively, in patients with liver cancer. Among these DEGs, 10 hub genes with high connected node values were identified, which were AURKA, BIRC5, BUB1B, CCNA2, CCNB1, CCNB2, CDC20, CDK1, DLGAP5 and MAD2L1. CDK1 and CCNB1 had the most connection nodes and the highest score and were therefore, the most significantly expressed. In addition, it was demonstrated that high expression levels of CDK1 and CCNB1 were associated with poor overall survival time of patients with liver cancer. Dihydroartemisinin (DHA) is a Food and Drug Administration-approved drug, which is derived from the traditional Chinese medicine Artemisia annua Linn. DHA inhibits cell proliferation in numerous cancer types, including liver cancer. In our previous study, it was revealed that DHA inhibited the proliferation of HepG2215 cells. In the present study, it was further demonstrated that DHA reduced the expression levels of CDK1 and CCNB1 in liver cancer. Overall, CDK1 and CCNB1 were the potential therapeutic targets of liver cancer, and DHA reduced the expression levels of CDK1 and CCNB1, and inhibited the proliferation of liver cancer cells.

Cisplatin promotes the expression level of PD-L1 in the microenvironment of hepatocellular carcinoma through YAP1.

Hepatocellular carcinoma (HCC) is one of the most lethal malignancies worldwide. However, the immune tolerance limits the effect of chemotherapeutic drugs. Therefore, the mechanism of cisplatin in promoting PD-L1 expression by YAP1 was investigated in the present study, and we found that cisplatin increased the expression level of YAP1 in the mouse liver with H22 cells. Meanwhile, cisplatin improved the expression level of PD-L1, IL-1ß and CCL2 in the tumor microenvironment. Further, cisplatin also enhanced the expression level of YAP1 in shYAP1 HepG2215 cells. The expression of PD-L1 was decreased by Verteporfin, YAP1 inhibitor, during the treatment of DEN/TCPOBOP-induced liver cancer in C57BL/6 mice. These results suggested that cisplatin could deteriorate the immunosuppressive microenvironment through increasing PD-L1, CCL2, IL-1ß by upregulated YAP1 expression. Therefore, the study suggested that YAP1 blockade destroyed the immunosuppressive microenvironment of cancer to improve the effect of chemotherapy in HCC.

Increased protein kinase C gamma activity induces Purkinje cell pathology in a mouse model of spinocerebellar ataxia 14.

Spinocerebellar ataxias (SCAs) are hereditary diseases leading to Purkinje cell degeneration and cerebellar dysfunction. Most forms of SCA are caused by expansion of CAG repeats similar to other polyglutamine disorders such as Huntington's disease. In contrast, in the autosomal dominant SCA-14 the disease is caused by mutations in the protein kinase C gamma (PKCγ) gene which is a well characterized signaling molecule in cerebellar Purkinje cells. The study of SCA-14, therefore, offers the unique opportunity to reveal the molecular and pathological mechanism eventually leading to Purkinje cell dysfunction and degeneration. We have created a mouse model of SCA-14 in which PKCγ protein with a mutation found in SCA-14 is specifically expressed in cerebellar Purkinje cells. We find that in mice expressing the mutated PKCγ protein the morphology of Purkinje cells in cerebellar slice cultures is drastically altered and mimics closely the morphology seen after pharmacological PKC activation. Similar morphological abnormalities were seen in localized areas of the cerebellum of juvenile transgenic mice in vivo. In adult transgenic mice there is evidence for some localized loss of Purkinje cells but there is no overall cerebellar atrophy. Transgenic mice show a mild cerebellar ataxia revealed by testing on the rotarod and on the walking beam. Our findings provide evidence for both an increased PKCγ activity in Purkinje cells in vivo and for pathological changes typical for cerebellar disease thus linking the increased and dysregulated activity of PKCγ tightly to the development of cerebellar disease in SCA-14 and possibly also in other forms of SCA.

Suppression of short interfering RNA-mediated gene silencing by the structural proteins of hepatitis C virus.

Viruses have evolved strategies to overcome the antiviral effects of the host at different levels. Besides specific defence mechanisms, the host responds to viral infection via the interferon pathway and also by RNA interference (RNAi). However, several viruses have been identified that suppress RNAi. We addressed the question of whether hepatitis C virus (HCV) suppresses RNAi, using cell lines constitutively expressing green fluorescent protein (GFP) and inducibly expressing HCV proteins. It was found that short interfering RNA-mediated GFP gene silencing was inhibited when the entire HCV polyprotein was expressed. Further studies showed that HCV structural proteins, and in particular envelope protein 2 (E2), were responsible for this inhibition. Co-precipitation assays demonstrated that E2 bound to Argonaute-2 (Ago-2), a member of the RNA-induced silencing complex, RISC. Thus, HCV E2 that interacts with Ago-2 is able to suppress RNAi.

Apoptosis and pathogenesis of melanoma and nonmelanoma skin cancer.

Skin cancers, i.e., basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma, belong to the most frequent tumors. Their formation is based on constitutional and/or inherited factors usually combined with environmental factors, mainly UV-irradiation through long term sun exposure. UV-light can randomly induce DNA damage in keratinocytes, but it can also mutate genes essential for control and surveillance in the skin epidermis. Various repair and safety mechanisms exist to maintain the integrity of the skin epidermis. For example, UV-light damaged DNA is repaired and if this is not possible, the DNA damaged cells are eliminated by apoptosis (sunburn cells). This occurs under the control of the p53 suppressor gene. Fas-ligand (FasL), a member of the tumor necrosis superfamily, which is preferentially expressed in the basal layer of the skin epidermis, is a key surveillance molecule involved in the elimination of sunburn cells, but also in the prevention of cell transformation. However, UV light exposure downregulates FasL expression in keratinocytes and melanocytes leading to the loss of its sensor function. This increases the risk that transformed cells are not eliminated anymore. Moreover, important control and surveillance genes can also be directly affected by UV-light. Mutation in the p53 gene is the starting point for the formation of SCC and some forms of BCC. Other BCCs originate through UV light mediated mutations of genes of the hedgehog signaling pathway which are essential for the maintainance of cell growth and differentiation. The transcription factor Gli2 plays a key role within this pathway, indeed, Gli2 is responsible for the marked apoptosis resistance of the BCCs. The formation of malignant melanoma is very complex. Melanocytes form nevi and from the nevi melanoma can develop through mutations in various genes. Once the keratinocytes or melanocytes have been transformed they re-express FasL which may allow the expanding tumor to evade the attack of immune effector cells. FasL which is involved in immune evasion or genes which govern the apoptosis resistance, e.g., Gli2 could therefore be prime targets to prevent tumor formation and growth. Attempts to silence these genes by RNA interference using gene specific short interfering RNAs (siRNAs) or short hairpin RNAs (shRNAs) have been functionally successful not only in tissue cultures and tumor tissues, but also in a mouse model. Thus, siRNAs and/or shRNAs may become a novel and promising approach to treat skin cancers at an early stage.

Gene silencing of transcription factor Gli2 inhibits basal cell carcinomalike tumor growth in vivo.

Basal cell carcinoma (BCC) belongs worldwide to the most frequent malignancy among Caucasians. The understanding of the molecular mechanisms of BCC formation, which is a prerequisite for the development of efficient new therapies, is still incomplete. The formation of sporadic BCCs in the skin is associated with uncontrolled hedgehog signaling, and the transcription factor Gli2 has been identified as a key mediator or effector of this signaling. There is indication in the literature that preventing Gli2 function may inhibit BCC formation and growth in vivo; however, the mechanism is unclear and difficult to study in humans. Therefore, we used a mouse tumor allograft model to investigate the role of Gli2 in tumor formation. A constitutively Gli2 expressing mouse tumor cell line was stably transfected with Gli2-specific shRNA to induce Gli2 gene silencing or with control shRNA. Injecting the Gli2 gene silenced cells into nude mice for tumor formation we detected a strongly retarded tumor growth compared with control tumor cells. Investigating the mechanisms, we found that Gli2 gene silencing has led to the disruption of the tumor structure as demonstrated by staining tumor sections with hematoxylin. Two main reasons for the tumor destruction were identified. We found that apoptosis was markedly increased while vascularization was strongly decreased in these tumors. Thus, important functions of the transcription factor Gli2 in this tumor model are the prevention of apoptosis and the promotion of microvascularization.

Role of apoptosis in basal cell and squamous cell carcinoma formation.

Long-term ultraviolet-light (UV) exposure of human skin epidermis is associated with an increased risk for the development of skin cancers, such as melanoma, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). UV radiation not only induces DNA damage in epidermal cells, it also interferes with skin homeostasis, which is maintained by a unique distribution pattern of apoptosis-inducing and -preventing molecules. If the DNA damage is not repaired or the damaged cells are not eliminated by apoptosis, the consequence can be cell transformation, uncontrolled proliferation and eventually skin tumor formation. An important "repair" gene is the p53 suppressor gene. Excessive UV exposure can mutate the p53 gene leading to the loss of its repair function and thus apoptosis resistance of the DNA-damaged cell. For BCC formation an additional pathway has been identified. Mutation of genes of the Hedgehog signaling pathway evokes the downregulation of apoptotic genes and upregulation of anti-apoptotic genes preventing the elimination of damaged cells. In addition, BCC and SCC strongly express the apoptosis-inducing Fas-ligand (FasL) which may help the tumor to escape the attack of immune effector cells. Silencing the genes involved in tumor formation by RNA interference might become a promising new approach to treat skin tumors.

Enhanced gene silencing by the application of multiple specific small interfering RNAs.

Small interfering RNA duplexes (siRNA) induce gene silencing in various eukaryotic cells, although usually in an incomplete manner. Using chemically synthesized siRNAs targeting the HIV-1 co-receptor CXCR4 or the apoptosis-inducing Fas-ligand (FasL), co-transfection of cells with two or more siRNA duplexes targeting different sites on the same mRNA resulted in an enhanced gene silencing compared with each single siRNA. This was shown in the down-regulation of protein and mRNA expression, and functionally in the inhibition of CXCR4-mediated HIV infection and of FasL-mediated cell apoptosis. Transfection efficiency determined for the FasL-specific siRNAs was dose-dependent and varied among the siRNAs tested, but was not the main reason for the enhanced gene silencing.

Fas ligand downregulation with antisense oligonucleotides in cells and in cultured tissues of normal skin epidermis and basal cell carcinoma.

Fas ligand (FasL), a member of the tumor necrosis factor family, induces apoptosis upon interaction with Fas-receptor-expressing cells. FasL normally plays an important immune regulatory role, but it can also cause severe skin diseases if overexpressed and it may serve some tumors for immune evasion. Thus, in situ inhibition of FasL expression with antisense oligonucleotides in patients may be a novel approach to overcome its pathogenic role. We designed and evaluated 15 phosphorothioate antisense oligonucleotides directed against different regions of the human FasL mRNA. They exhibited different inhibitory activities on FasL expression in HEK293 cells. The most potent antisense oligonucleotide, ASO8, specifically downregulated 90% FasL expression at the protein level and 80% at the mRNA level. FasL downregulation reduced the effector function of HEK293 cells toward Fas receptor positive target cells. Further studies demonstrated that ASO8 efficiently inhibited FasL synthesis in split skin and basal cell carcinoma tissue. Our results show that the modulation of FasL expression by antisense oligonucleotides is possible in cells as well as tissue and indicate that antisense oligonucleotides may provide a promising strategy for the therapy of FasL-mediated disorders.