Recurrent HBV Integration Targets as Potential Drivers in Hepatocellular Carcinoma.

Chronic hepatitis B virus (HBV) infection is the major etiology of hepatocellular carcinoma (HCC), frequently with HBV integrating into the host genome. HBV integration, found in 85% of HBV-associated HCC (HBV-HCC) tissue samples, has been suggested to be oncogenic. Here, we investigated the potential of HBV-HCC driver identification via the characterization of recurrently targeted genes (RTGs). A total of 18,596 HBV integration sites from our in-house study and others were analyzed. RTGs were identified by applying three criteria: at least two HCC subjects, reported by at least two studies, and the number of reporting studies. A total of 396 RTGs were identified. Among the 28 most frequent RTGs, defined as affected in at least 10 HCC patients, 23 (82%) were associated with carcinogenesis and 5 (18%) had no known function. Available breakpoint positions from the three most frequent RTGs, TERT, MLL4/KMT2B, and PLEKHG4B, were analyzed. Mutual exclusivity of TERT promoter mutation and HBV integration into TERT was observed. We present an RTG consensus through comprehensive analysis to enable the potential identification and discovery of HCC drivers for drug development and disease management.

Virion-associated phosphatidylethanolamine promotes TIM1-mediated infection by Ebola, dengue, and West Nile viruses.

Phosphatidylserine (PS) receptors contribute to two crucial biological processes: apoptotic clearance and entry of many enveloped viruses. In both cases, they recognize PS exposed on the plasma membrane. Here we demonstrate that phosphatidylethanolamine (PE) is also a ligand for PS receptors and that this phospholipid mediates phagocytosis and viral entry. We show that a subset of PS receptors, including T-cell immunoglobulin (Ig) mucin domain protein 1 (TIM1), efficiently bind PE. We further show that PE is present in the virions of flaviviruses and filoviruses, and that the PE-specific cyclic peptide lantibiotic agent Duramycin efficiently inhibits the entry of West Nile, dengue, and Ebola viruses. The inhibitory effect of Duramycin is specific: it inhibits TIM1-mediated, but not L-SIGN-mediated, virus infection, and it does so by blocking virus attachment to TIM1. We further demonstrate that PE is exposed on the surface of apoptotic cells, and promotes their phagocytic uptake by TIM1-expressing cells. Together, our data show that PE plays a key role in TIM1-mediated virus entry, suggest that disrupting PE association with PS receptors is a promising broad-spectrum antiviral strategy, and deepen our understanding of the process by which apoptotic cells are cleared.

ADAM17 activity and other mechanisms of soluble L-selectin production during death receptor-induced leukocyte apoptosis.

L-selectin is an adhesion molecule expressed by neutrophils that broadly directs their infiltration in to sites of inflammation. It is also present at relatively high levels in the serum of normal individuals. It is well established that L-selectin is efficiently shed from the surface of neutrophils upon their activation, a process that regulates its density and binding activity. Neutrophil programmed cell death is critical for the resolution of inflammation, and L-selectin downregulation is induced during this process as well. The mechanisms underpinning this latter process are much less understood, and were investigated in this study. Using a disintegrin and metalloprotease (ADAM)-17 radiation chimeric mice, we demonstrate for the first time that during early events of death receptor-mediated neutrophil apoptosis, L-selectin downregulation occurs primarily by ADAM17-mediated shedding. This was observed as well upon using shRNA to knock down ADAM17 expression in Jurkat cells, a well-studied cell line in terms of the molecular processes involved in the induction of apoptosis. These findings directly reveal that ADAM17 activity occurs during programmed cell death. Hence, the cleavage of particular ADAM17 substrates may be an additional component of the anti-inflammatory program initiated by apoptotic neutrophils. Of interest was that during later stages of induced leukocyte apoptosis, soluble L-selectin production occurred independent of ADAM17, as well as membrane events, such as blebbing and microparticle production. This process may provide an explanation for the lack of diminished serum L-selectin levels in ADAM17-null mice, and suggests a mechanism for the homeostatic maintenance of soluble L-selectin levels in the blood of healthy individuals.