Diego Calabrese

Simultaneous detection of hepatitis C virus and interferon stimulated gene expression in infected human liver

Approximately 50% of patients with chronic hepatitis C (CHC) have ongoing expression of interferon stimulated genes (ISGs) in the liver. It is unclear why this endogenous antiviral response is inefficient in eradicating the infection. Several viral escape strategies have been identified in vitro, including inhibition of interferon (IFN) induction and ISG messenger RNA (mRNA) translation. The in vivo relevance of these mechanisms is unknown, because reliable methods to identify hepatitis C virus (HCV)‐infected cells in human liver are lacking. We developed a highly sensitive in situ hybridization (ISH) system capable of HCV RNA and ISG mRNA detection in human liver biopsies and applied it to study the interaction of HCV with the endogenous IFN system. We simultaneously monitored HCV RNA and ISG mRNA using HCV isolate‐ and ISG mRNA‐specific probes in liver biopsy sections from 18 CHC patients. The signals were quantified at the single‐cell resolution in a series of random high‐power fields. The proportion of infected hepatocytes ranged from 1%‐54% and correlated with viral load, but not with HCV genotype or ISG expression. Infected cells occurred in clusters, pointing to cell‐to‐cell spread as the predominant mode of HCV transmission. ISG mRNAs were readily detected in HCV‐infected cells, challenging previously proposed mechanisms of viral interference with the immune system. Conversely, infected cells and neighboring cells showed increased ISG mRNA levels, demonstrating that the stimulus driving ISG expression originates from HCV‐infected hepatocytes. Conclusion: HCV infection in human hepatocytes during CHC does not efficiently interfere with IFN induction, IFN signaling, or transcription of ISG mRNA. (Hepatology 2014;59:2121–2130)

Clearance of persistent hepatitis C virus infection in humanized mice using a claudin-1-targeting monoclonal antibody

Hepatitis C virus (HCV) infection is a leading cause of liver cirrhosis and cancer. Cell entry of HCV and other pathogens is mediated by tight junction (TJ) proteins, but successful therapeutic targeting of TJ proteins has not been reported yet. Using a human liver–chimeric mouse model, we show that a monoclonal antibody specific for the TJ protein claudin-1 (ref. 7) eliminates chronic HCV infection without detectable toxicity. This antibody inhibits HCV entry, cell-cell transmission and virus-induced signaling events. Antibody treatment reduces the number of HCV-infected hepatocytes in vivo, highlighting the need for de novo infection by means of host entry factors to maintain chronic infection. In summary, we demonstrate that an antibody targeting a virus receptor can cure chronic viral infection and uncover TJ proteins as targets for antiviral therapy.

Tumor infiltration by FcγRIII (CD16)+ myeloid cells is associated with improved survival in patients with colorectal carcinoma

The prognostic significance of macrophage and natural killer (NK) cell infiltration in colorectal carcinoma (CRC) microenvironment is unclear. We investigated the CRC innate inflammatory infiltrate in over 1,600 CRC using two independent tissue microarrays and immunohistochemistry. Survival time was assessed using the Kaplan–Meier method and Cox proportional hazards regression analysis in a multivariable setting. Spearmans rank correlation tested the association between macrophage and lymphocyte infiltration. The Basel study included over 1,400 CRCs. The level of CD16+ cell infiltration correlated with that of CD3+ and CD8+ lymphocytes but not with NK cell infiltration. Patients with high CD16+ cell infiltration (score 2) survived longer than patients with low (score 1) infiltration (p = 0.008), while no survival difference between patients with score 1 or 2 for CD56+ (p = 0.264) or CD57+ cell (p = 0.583) infiltration was detected. CD16+ infiltrate was associated with improved survival even after adjusting for known prognostic factors including pT, pN, grade, vascular invasion, tumor growth and age [(p = 0.001: HR (95% CI) = 0.71 (0.6–0.9)]. These effects were independent from CD8+ lymphocyte infiltration [(p = 0.036: HR (95% CI) = 0.81 (0.7–0.9)] and presence of metastases [(p = 0.002: HR (95% CI) = 0.43 (0.3–0.7)]. Phenotypic studies identified CD16+ as CD45+CD33+CD11b+CD11c+ but CD64− HLA‐DR‐myeloid cells. Beneficial effects of CD16+ cell infiltration were independently validated by a study carried out at the University of Athens confirming that patients with CD16 score 2 survived longer than patients with score 1 CRCs (p = 0.011). Thus, CD16+ cell infiltration represents a novel favorable prognostic factor in CRC.

IFN-λ receptor 1 expression is induced in chronic hepatitis C and correlates with the IFN-λ3 genotype and with nonresponsiveness to IFN-α therapies

Liver biopsies from patients with chronic hepatitis C reveal high IFN-λR1 expression, which can be induced with IFN-α and is associated with elevated ISG expression, the IFN-λ3 minor alleles, and nonresponsiveness to peg-IFN-α and ribavirin therapy.

Mesenchymal stromal cells induce epithelial-to-mesenchymal transition in human colorectal cancer cells through the expression of surface-bound TGF-β

Mesenchymal stem/stromal cells (MSC) are multipotent precursors endowed with the ability to home to primary and metastatic tumor sites, where they can integrate into the tumor‐associated stroma. However, molecular mechanisms and outcome of their interaction with cancer cells have not been fully clarified. In this study, we investigated the effects mediated by bone marrow‐derived MSC on human colorectal cancer (CRC) cells in vitro and in vivo. We found that MSC triggered epithelial‐to‐mesenchymal transition (EMT) in tumor cells in vitro, as indicated by upregulation of EMT‐related genes, downregulation of E‐cadherin and acquisition of mesenchymal morphology. These effects required cell‐to‐cell contact and were mediated by surface‐bound TGF‐β newly expressed on MSC upon coculture with tumor cells. In vivo tumor masses formed by MSC‐conditioned CRC cells were larger and characterized by higher vessel density, decreased E‐cadherin expression and increased expression of mesenchymal markers. Furthermore, MSC‐conditioned tumor cells displayed increased invasiveness in vitro and enhanced capacity to invade peripheral tissues in vivo. Thus, by promoting EMT‐related phenomena, MSC appear to favor the acquisition of an aggressive phenotype by CRC cells.

Pegylated IFN-α regulates hepatic gene expression through transient Jak/STAT activation

The use of pegylated interferon-α (pegIFN-α) has replaced unmodified recombinant IFN-α for the treatment of chronic viral hepatitis. While the superior antiviral efficacy of pegIFN-α is generally attributed to improved pharmacokinetic properties, the pharmacodynamic effects of pegIFN-α in the liver have not been studied. Here, we analyzed pegIFN-α-induced signaling and gene regulation in paired liver biopsies obtained prior to treatment and during the first week following pegIFN-α injection in 18 patients with chronic hepatitis C. Despite sustained high concentrations of pegIFN-α in serum, the Jak/STAT pathway was activated in hepatocytes only on the first day after pegIFN-α administration. Evaluation of liver biopsies revealed that pegIFN-α induces hundreds of genes that can be classified into four clusters based on different temporal expression profiles. In all clusters, gene transcription was mainly driven by IFN-stimulated gene factor 3 (ISGF3). Compared with conventional IFN-α therapy, pegIFN-α induced a broader spectrum of gene expression, including many genes involved in cellular immunity. IFN-induced secondary transcription factors did not result in additional waves of gene expression. Our data indicate that the superior antiviral efficacy of pegIFN-α is not the result of prolonged Jak/STAT pathway activation in hepatocytes, but rather is due to induction of additional genes that are involved in cellular immune responses.

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.

VEGF dose regulates vascular stabilization through Semaphorin3A and the Neuropilin-1+ monocyte/TGF-β1 paracrine axis

VEGF is widely investigated for therapeutic angiogenesis, but while short‐term delivery is desirable for safety, it is insufficient for new vessel persistence, jeopardizing efficacy. Here, we investigated whether and how VEGF dose regulates nascent vessel stabilization, to identify novel therapeutic targets. Monoclonal populations of transduced myoblasts were used to homogeneously express specific VEGF doses in SCID mouse muscles. VEGF was abrogated after 10 and 17 days by Aflibercept treatment. Vascular stabilization was fastest with low VEGF, but delayed or prevented by higher doses, without affecting pericyte coverage. Rather, VEGF dose‐dependently inhibited endothelial Semaphorin3A expression, thereby impairing recruitment of Neuropilin‐1‐expressing monocytes (NEM), TGF‐β1 production and endothelial SMAD2/3 activation. TGF‐β1 further initiated a feedback loop stimulating endothelial Semaphorin3A expression, thereby amplifying the stabilizing signals. Blocking experiments showed that NEM recruitment required endogenous Semaphorin3A and that TGF‐β1 was necessary to start the Semaphorin3A/NEM axis. Conversely, Semaphorin3A treatment promoted NEM recruitment and vessel stabilization despite high VEGF doses or transient adenoviral delivery. Therefore, VEGF inhibits the endothelial Semaphorin3A/NEM/TGF‐β1 paracrine axis and Semaphorin3A treatment accelerates stabilization of VEGF‐induced angiogenesis.

Induction of hypoxia and necrosis in multicellular tumor spheroids is associated with resistance to chemotherapy treatment

Culture of cancerous cells in standard monolayer conditions poorly mirrors growth in three-dimensional architectures typically observed in a wide majority of cancers of different histological origin. Multicellular tumor spheroid (MCTS) culture models were developed to mimic these features. However, in vivo tumor growth is also characterized by the presence of ischemic and necrotic areas generated by oxygenation gradients and differential access to nutrients. Hypoxia and necrosis play key roles in tumor progression and resistance to treatment. To provide in vitro models recapitulating these events in highly controlled and standardized conditions, we have generated colorectal cancer (CRC) cell spheroids of different sizes and analyzed their gene expression profiles and sensitivity to treatment with 5FU, currently used in therapeutic protocols. Here we identify three MCTS stages, corresponding to defined spheroid sizes, characterized by normoxia, hypoxia, and hypoxia plus necrosis, respectively. Importantly, we show that MCTS including both hypoxic and necrotic areas most closely mimic gene expression profiles of in vivo-developing tumors and display the highest resistance to 5FU. Taken together, our data indicate that MCTS may mimic in vitro generation of ischemic and necrotic areas in highly standardized and controlled conditions, thereby qualifying as relevant models for drug screening purposes.

miR-135a-5p-mediated downregulation of protein tyrosine phosphatase receptor delta is a candidate driver of HCV-associated hepatocarcinogenesis

Background and aims HCV infection is a leading risk factor of hepatocellular carcinoma (HCC). However, even after viral clearance, HCC risk remains elevated. HCV perturbs host cell signalling to maintain infection, and derailed signalling circuitry is a key driver of carcinogenesis. Since protein phosphatases are regulators of signalling events, we aimed to identify phosphatases that respond to HCV infection with relevance for hepatocarcinogenesis. Methods We assessed mRNA and microRNA (miRNA) expression profiles in primary human hepatocytes, liver biopsies and resections of patients with HCC, and analysed microarray and RNA-seq data from paired liver biopsies of patients with HCC. We revealed changes in transcriptional networks through gene set enrichment analysis and correlated phosphatase expression levels to patient survival and tumour recurrence. Results We demonstrate that tumour suppressor protein tyrosine phosphatase receptor delta (PTPRD) is impaired by HCV infection in vivo and in HCC lesions of paired liver biopsies independent from tissue inflammation or fibrosis. In liver tissue adjacent to tumour, high PTPRD levels are associated with a dampened transcriptional activity of STAT3, an increase of patient survival from HCC and reduced tumour recurrence after surgical resection. We identified miR-135a-5p as a mechanistic regulator of hepatic PTPRD expression in patients with HCV. Conclusions We previously demonstrated that STAT3 is required for HCV infection. We conclude that HCV promotes a STAT3 transcriptional programme in the liver of patients by suppressing its regulator PTPRD via upregulation of miR-135a-5p. Our results show the existence of a perturbed PTPRD–STAT3 axis potentially driving malignant progression of HCV-associated liver disease.