Hepatitis B virus (HBV) infection could cause hepatitis, liver cirrhosis, and hepatocellular carcinoma. HBV-mediated pathogenesis is only partially understood, but X protein (HBx) reportedly possesses oncogenic potential. Exosomes are small membrane vesicles with diverse functions released by various cells including hepatocytes, and HBV harnesses cellular exosome biogenesis and export machineries for virion morphogenesis and secretion. Therefore, HBV infection might cause changes in exosome contents with functional implications for both virus and host. In this work, exosome protein content changes induced by HBV and HBx were quantitatively analyzed by SILAC/LC–MS/MS. Exosomes prepared from SILAC-labeled hepatoma cell line Huh-7 transfected with HBx, wildtype, or HBx-null HBV replicon plasmids were analyzed by LC–MS/MS. Systematic analyses of MS data and confirmatory immunoblotting showed that HBx overexpression and HBV, with or without HBx, replication in Huh-7 cells indeed caused marked and specific changes in exosome protein contents. Furthermore, specific changes in protein contents were also detected in exosomes purified from HBV-infected patients’ sera compared with control sera negative for HBV markers. These results illustrate a new aspect of interactions between HBV and the host and provide the foundation for future research into roles played by exosomes in HBV infection and pathogenesis.Keywords: exosome; HBV; HBx; hepatocyte; patient serum; SILAC; VCP;

•Malignant melanoma initiating cells promote melanoma metastasis depending on ABCB5.•ABCB5 is an important promoter for melanoma metastasis.•ABCB5 drives melanoma metastasis through enhancing NF-kB p65 protein stability.Melanoma is the most aggressive type of skin cancer. Melanoma has an extremely poor prognosis because of its high potential for vascular invasion, metastasis and recurrence. The mechanism of melanoma metastasis is not well understood. ATP-binding cassette sub-family B member 5 (ABCB5) plays a key role in melanoma growth. However, it is uncertain what function ABCB5 may exert in melanoma metastasis. In this report, we for the first time demonstrate ABCB5 as a crucial factor that promotes melanoma metastasis. ABCB5 positive (ABCB5+) malignant melanoma initiating cells (MMICs) display a higher metastatic potential compared with ABCB5 negative (ABCB5-) melanoma subpopulation. Knockdown of ABCB5 expression reduces melanoma cell migration and invasion in vitro and melanoma pulmonary metastasis in tumor xenograft mice. ABCB5 and NF-κB p65 expression levels are positively correlated in both melanoma tissues and cell lines. Consequently, ABCB5 activates the NF-κB pathway by inhibiting p65 ubiquitination to enhance p65 protein stability. Our finding highlights ABCB5 as a novel pro-metastasis factor and provides a potential therapeutic target for melanoma.

Aberrant activation of the Wnt/β-catenin pathway is frequent in hepatocellular carcinoma (HCC) and contributes to HCC initiation and progression. This abnormal activation may result from somatic mutations in the genes of the Wnt/β-catenin pathway and/or dysregulation of the Wnt/β-catenin pathway. The mechanism for the latter remains poorly understood. Prospero-related homeobox 1 (PROX1) is a downstream target of the Wnt/β-catenin pathway in human colorectal cancer and elevated PROX1 expression promotes malignant progression. However, the Wnt/β-catenin pathway does not regulate PROX1 expression in the liver and HCC cells. Here we report that PROX1 promotes HCC cell proliferation in vitro and tumor growth in HCC xenograft mice. PROX1 and β-catenin levels are positively correlated in tumor tissues as well as in cultured HCC cells. PROX1 can upregulate β-catenin transcription by stimulating the β-catenin promoter and enhance the nuclear translocation of β-catenin in HCC cells, which leads to the activation of the Wnt/β-catenin pathway. Moreover, we show that increase in PROX1 expression renders HCC cells more resistant to sorafenib treatment, which is the standard therapy for advanced HCC. Overall, we have pinpointed PROX1 as a critical factor activating the Wnt/β-catenin pathway in HCC, which promotes HCC proliferation and sorafenib resistance.

Chronic infection of hepatitis B virus (HBV) presents one of the serious public health challenges worldwide. Current treatment of chronic hepatitis B (CHB) is limited, and is composed of interferon and nucleoside/nucleotide reverse transcriptase inhibitors (NRTI). Interferon is poorly tolerated and is only responsive in a small fraction of CHB patients and NRTIs often face the problem of emergence of drug resistance during long-term treatment. The current treatment of CHB can be improved in several ways including genotyping mutations associated with drug resistance before treatment to guide the choice of NRTIs and suitable combinations among NRTIs and interferon. It is important to continue research in the identification of novel therapeutic targets in the life cycle of HBV or in the host immune system to stimulate the development of new antiviral agents and immunotherapies. Several antiviral agents targeting HBV entry, cccDNA, capsid formation, viral morphogenesis and virion secretion, as well as two therapeutic vaccines are currently being evaluated in preclinical studies or in clinical trials to assess their anti-HBV efficacy.

Co-circulation of subgenotypes IA and IB of hepatitis A virus (HAV) has been reported in South Africa, South America, Europe, and the United States. In this study, phylogenetic and recombination analyses were performed for the first time on 31 complete HAV genomes from infected humans and simians. Three potentially significant intra-genotypic recombination events (I–III) were identified by recombination detection analysis. Recombination events I and II occurred between the lineages represented, respectively, by the Japanese isolate AH2 (AB020565, subgenotype IA) and the North African isolate MBB (M20273, subgenotype IB), giving rise to the recombinant Uruguayan isolate HAV5 (EU131373). Recombination event III occurred between the lineages represented, respectively, by the North African isolate MBB (M20273, subgenotype IB) and the German isolate GBM (X75215, subgenotype IA), resulting in the Italian isolate FG (X83302). The findings demonstrate that humans can be co-infected with different HAV subgenotypes and provide valuable hints for future research on HAV diversity.

Due to its high similarity to human hepatitis B virus (HBV), duck HBV (DHBV) is often used as an important model for HBV research. While inter-genotypic recombination of HBV is common, it has not been reported with DHBV. In this study, 32 non-redundant DHBV complete genomes were analyzed using phylogenetic methods and classified into two clusters, corresponding to the ‘Chinese’ and ‘Western country’ branches previously reported based on geographical distribution. One ‘Chinese’ branch strain was isolated in Australia and three ‘Western country’ branch strains were isolated in China, suggesting cross-geographical distribution of both branches. Recombination analyses of the 32 DHBV genomes identified two possible inter-genotypic recombination events with high confidence value. These recombination events occurred between the lineages represented, respectively, by the Chinese isolate GD3 (AY536371, ‘Chinese’ branch) and the American isolate DHBV16 (K01834, ‘Western country’ branch), giving rise to two Chinese recombinant isolates CH4 (EU429324) and CH6 (EU429326). The identification of inter-genotypic recombination among circulating DHBV isolates suggests the usefulness of DHBV as a model for studying the mechanism of HBV recombination.