Transition to HBeAg-negative chronic hepatitis B virus infection is associated with reduced cccDNA transcriptional activity.

BACKGROUND & AIMS: HBeAg seroconversion during the natural history of chronic hepatitis B (CHB) is associated with a strong drop in serum HBV DNA levels and a reduction of intrahepatic covalently closed circular DNA (cccDNA) content. Of particular interest is the transition to HBeAg-negative chronic infection (ENCI). ENCI, previously known as inactive carrier state, is characterized by very low or negative viremia and the absence of liver disease. The molecular mechanisms responsible for the transition to ENCI and for the control of viral replication in ENCI are still poorly understood. METHODS: To identify which step(s) in the viral life cycle are controlled during the transition to ENCI, we quantified cccDNA, pre-genomic RNA (pgRNA), total HBV RNA and DNA replicative intermediates in 68 biopsies from patients in different phases of CHB. RESULTS: HBeAg seroconversion is associated with a reduction of cccDNA amounts as well as transcriptional activity. Silencing of cccDNA is particularly pronounced in ENCI, where there was ~46 times less pgRNA per cccDNA compared to HBeAg-negative CHB. Furthermore, a subgroup of patients with HBeAg-negative CHB can be characterized by reduced replication efficiency downstream of pgRNA. CONCLUSIONS: The reduction in serum viral load during the transition to ENCI seems to primarily result from strong inhibition of the transcriptional activity of cccDNA which can be maintained in the absence of liver disease. LAY SUMMARY: During the natural course of chronic hepatitis B virus infections, the immune response can gain control of viral replication. Quantification of viral DNA and RNA in liver biopsies of patients in different stages of chronic hepatitis B allowed us to identify the steps in the viral life cycle that are affected during the transition from active to inactive disease. Therapeutic targeting of these steps might induce sustained inhibition of viral transcription.

Protein phosphatase 2A promotes hepatocellular carcinogenesis in the diethylnitrosamine mouse model through inhibition of p53.

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide. Most HCCs develop in cirrhotic livers. Alcoholic liver disease, chronic hepatitis B and chronic hepatitis C are the most common underlying liver diseases. Hepatitis C virus (HCV)-specific mechanisms that contribute to HCC are presently unknown. Transgenic expression of HCV proteins in the mouse liver induces an overexpression of the protein phosphatase 2A catalytic subunit (PP2Ac). We have previously reported that HCV-induced PP2Ac overexpression modulates histone methylation and acetylation and inhibits DNA damage repair. In this study, we analyze tumor formation and gene expression using HCV transgenic mice that overexpress PP2Ac and liver tissues from patients with HCC. We demonstrate that PP2Ac overexpression interferes with p53-induced apoptosis. Injection of the carcinogen, diethylnitrosamine, induced significantly more and larger liver tumors in HCV transgenic mice that overexpress PP2Ac compared with control mice. In human liver biopsies from patients with HCC, PP2Ac expression was significantly higher in HCC tissue compared with non-tumorous liver tissue from the same patients. Our findings demonstrate an important role of PP2Ac overexpression in liver carcinogenesis and provide insights into the molecular pathogenesis of HCV-induced HCC.

Human cytokines activate JAK-STAT signaling pathway in porcine ocular tissue.

BACKGROUND: The JAK/STAT (Janus Tyrosine Kinase, Signal Transducers and Activators of Transcription) pathway is associated with cytokine or growth factor receptors and it is critical for growth control, developmental regulation and homeostasis. The use of porcine ocular cells as putative xenotransplants appears theoretically possible. The aim of this study was to investigate the response of various porcine ocular cells in vitro to human cytokines in regard to the activation of JAK-STAT signaling pathways. METHODS: Porcine lens epithelial cells, pigmented iris epithelial cells and pigmented ciliary body cells were used in this study. These cells were isolated from freshly enucleated porcine eyes by enzymatic digestion. Cultured cells between passages 3-8 were used in all experiments. Electromobility shift assay (EMSA), proliferation assay, immunofluorescence staining and flow cytometry were used to evaluate the JAK-STAT signaling pathway in these cells. RESULTS: JAK/STAT signaling pathways could be activated in porcine pigmented epithelial ciliary body cells, in pigmented iris epithelial cells and in lens epithelial cells in response to porcine and human interferons and cytokines. All cells showed very strong STAT1 activation upon stimulation with porcine interferon-gamma. Porcine ocular cells also respond to human cytokines; IFN-alpha induced strong activation of STAT1 in EMSA, flow cytometry and immunofluorescence experiments whereas activation of STAT3 was less strong in EMSA, but strong in flow cytometry and immunofluorescence. Human recombinant IL-6 activated STAT3 and human IL-4 activated STAT6. With the help of immunofluorescence assay and flow cytometry we observed nuclear localization of STAT proteins after activation of porcine ocular cells with cytokines and interferons. Human IFN-α had an inhibitory effect on porcine ocular cells in proliferation assays. CONCLUSION: Our study demonstrated that some types of human cytokines and interferon activate intracellular JAK-STAT signaling pathways in porcine ocular cells. We hypothesize that direct stimulation of the JAK-STAT pathway in porcine cells in response to human cytokines will lead to complications or failure, if pig-to-human ocular tissue xenotransplantation were to be carried out. For successful xenotransplantation among other obstacles there must be new approaches developed to regulate signaling pathways.

Integrative proteogenomic characterization of hepatocellular carcinoma across etiologies and stages.

Proteogenomic analyses of hepatocellular carcinomas (HCC) have focused on early-stage, HBV-associated HCCs. Here we present an integrated proteogenomic analysis of HCCs across clinical stages and etiologies. Pathways related to cell cycle, transcriptional and translational control, signaling transduction, and metabolism are dysregulated and differentially regulated on the genomic, transcriptomic, proteomic and phosphoproteomic levels. We describe candidate copy number-driven driver genes involved in epithelial-to-mesenchymal transition, the Wnt-ß-catenin, AKT/mTOR and Notch pathways, cell cycle and DNA damage regulation. The targetable aurora kinase A and CDKs are upregulated. CTNNB1 and TP53 mutations are associated with altered protein phosphorylation related to actin filament organization and lipid metabolism, respectively. Integrative proteogenomic clusters show that HCC constitutes heterogeneous subgroups with distinct regulation of biological processes, metabolic reprogramming and kinase activation. Our study provides a comprehensive overview of the proteomic and phophoproteomic landscapes of HCCs, revealing the major pathways altered in the (phospho)proteome.

The Retinal Pigment Epithelial Cell Line (ARPE-19) Displays Mosaic Structural Chromosomal Aberrations.

The retinal pigment epithelial cell line ARPE-19 was established in 1996 and remains widely used today for biomedical and in particular ophthalmology research. We have analyzed the chromosomes of the ARPE-19 cell line and found cultured cells exist as a heterogeneous mixture having both normal karyotypes and chromosomal rearrangements. In ARPE-19 cells, we observed metaphases with a single translocation t(15;19) and metaphases with two translocations t(5;15) and t(15;19) and a derivative chromosome 9. Aneuploidies have also been detected (monosomy: -16; trisomy: +11, +18). Multiple attempts to isolate clones with a normal karyotype from those with aberrant karyotypes failed due to senescence of cells of normal karyotypes. We could, however, isolate clones with the translocation t(15;19) and clones with two translocations t(5;15) and t(15;19). In continued cell culture after second subcloning for 30 passages, all clones maintained their cytogenetic integrity.We have further investigated the chromosomal profiles of the ARPE-19 cell line from another laboratory and observed cells with a normal karyotype as well as abnormalities in chromosomes 6p and 11q. The DNA profiles of the ARPE-19 cells from both labs were identical to the ATCC profiles, excluding contamination with other cell lines. Since chromosomal translocations in ARPE-19 cells differ from lab to lab and display a mosaicism for structural chromosomal aberrations, researchers dealing with ARPE-19 cells should screen their stocks for chromosomal aberrations and proceed with caution against misinterpretations during experimental manipulations with this cell line. This chapter describes in detail our laboratory methods for single cell cloning, karyotype analysis and fluorescence in situ hybridization (FISH), which we used for the identification and characterization of chromosomal translocations in the retinal pigment epithelial cell line ARPE-19.

Gastrin releasing peptide-preferring bombesin receptors mediate growth of human renal cell carcinoma.

Bombesin-like peptides typically act as neurotransmitters along the brain-gut axis and as growth factors in various human tissues. The present study demonstrates the expression of gastrin releasing peptide (GRP)-preferring bombesin receptors in human renal cell carcinoma but not in normal kidney tissue. The expression of GRP receptors was characterized at the mRNA level by reverse transcription-PCR, as well as at the protein level by binding of (125)I-[Tyr(4)] bombesin to membranes prepared from tumor tissue (K(d) 0.3 nM) and healthy kidney tissue from the same four patients. GRP receptors were also demonstrated in four human kidney carcinoma cell lines (A-498, CAKI-1, CAKI-2, and ACHN). The effects of bombesin/GRP agonists and/or antagonists on growth were investigated in vitro on CAKI-2 cells, which expressed large amounts of GRP receptors. Cell numbers stimulated by 10% fetal calf serum were significantly stimulated by interleukin-1beta (control) and GRP-7 (10(-7) M), both in the range of 136 to 148%; addition of the GRP receptor antagonist acetyl-GRP(20-27) (10(-6) M) completely reversed this effect. Bombesin alone (10(-6) M) significantly stimulated CAKI-2 cells (129%) cultured with 0.5% fetal calf serum, whereas another antagonist, D-Phe6,Leu13,(CH2NH)Leu14 bombesin(6-14) (1 microM), alone did not inhibit growth, thus excluding an autocrine mechanism. These results indicate for the first time that malignant transformation of human kidney tissue into renal cell carcinoma is accompanied by novel expression of GRP receptors. Bombesin-like peptides might act as mitogens in these carcinomas, and they might be useful as diagnostic or therapeutic tools such as tumor imaging or internal radiotherapy.