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Mutations in the gene encoding isocitrate dehydrogenase 2 (IDH2) occur in several types of cancer, including acute myeloid leukemia (AML). In model systems, mutant IDH2 causes hematopoietic differentiation arrest. Enasidenib, a selective small-molecule inhibitor of mutant IDH2, produces a clinical response in 40% of treated patients with relapsed/refractory AML by promoting leukemic cell differentiation. Here, we studied the clonal basis of response and acquired resistance to enasidenib treatment. Using sequential patient samples, we determined the clonal structure of hematopoietic cell populations at different stages of differentiation. Before therapy, IDH2-mutant clones showed variable differentiation arrest. Enasidenib treatment promoted hematopoietic differentiation from either terminal or ancestral mutant clones; less frequently, treatment promoted differentiation of nonmutant cells. Analysis of paired diagnosis/relapse samples did not identify second-site mutations in IDH2 at relapse. Instead, relapse arose by clonal evolution or selection of terminal or ancestral clones, thus highlighting multiple bypass pathways that could potentially be targeted to restore differentiation arrest. These results show how mapping of clonal structure in cell populations at different stages of differentiation can reveal the response and evolution of clones during treatment response and relapse.

Despite the high response rates of individuals with myelodysplastic syndrome (MDS) with deletion of chromosome 5q (del(5q)) to treatment with lenalidomide (LEN) and the recent identification of cereblon (CRBN) as the molecular target of LEN, the cellular mechanism by which LEN eliminates MDS clones remains elusive. Here we performed an RNA interference screen to delineate gene regulatory networks that mediate LEN responsiveness in an MDS cell line, MDSL. We identified GPR68, which encodes a G-protein-coupled receptor that has been implicated in calcium metabolism, as the top candidate gene for modulating sensitivity to LEN. LEN induced GPR68 expression via IKAROS family zinc finger 1 (IKZF1), resulting in increased cytosolic calcium levels and activation of a calcium-dependent calpain, CAPN1, which were requisite steps for induction of apoptosis in MDS cells and in acute myeloid leukemia (AML) cells. In contrast, deletion of GPR68 or inhibition of calcium and calpain activation suppressed LEN-induced cytotoxicity. Moreover, expression of calpastatin (CAST), an endogenous CAPN1 inhibitor that is encoded by a gene (CAST) deleted in del(5q) MDS, correlated with LEN responsiveness in patients with del(5q) MDS. Depletion of CAST restored responsiveness of LEN-resistant non-del(5q) MDS cells and AML cells, providing an explanation for the superior responses of patients with del(5q) MDS to LEN treatment. Our study describes a cellular mechanism by which LEN, acting through CRBN and IKZF1, has cytotoxic effects in MDS and AML that depend on a calcium- and calpain-dependent pathway.

A series of bicyclic pyrazole carboxamides was synthesized and tested for inhibitory activity against the class III deacetylase sirtuin enzymes. Moderate to low micromolar inhibitory activities were obtained against SIRT1 and SIRT2. These bicyclic pyrazole compounds represent a new class of sirtuin inhibitors with a preference for SIRT1 over SIRT2., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Background & Aims: Rebleeding after an initial oesophageal variceal haemorrhage remains a significant problem despite therapy with band ligation, non-selective β-blockers or a combination of these. Carvedilol is a vasodilating non-selective β-blocker with alpha-1 receptor and calcium channel antagonism. A recent study has suggested it is effective in the prevention of a first variceal bleed. Our aim was to compare oral carvedilol with variceal band ligation (VBL) in the prevention of rebleeding following a first variceal bleed., Methods: Patients who were stable 5 days after presentation with a first oesophageal variceal haemorrhage and had not been taking β-blockers were randomised to oral carvedilol or VBL. Patients were followed-up after one week, monthly, then every 3 months. The primary end point was variceal rebleeding on intention-to-treat analysis., Results: 64 patients were randomised, 33 to carvedilol and 31 to VBL. 58 (90.6%) patients had alcohol related liver disease. Age and Child-Pugh score were similar in both groups at baseline. Median follow-up was 26.3 (interquartile range [IQR] 10.2-46.6)months. Compliance was 68% and 65% for carvedilol and VBL respectively (p=0.993) and serious adverse events between the two groups were similar (p=0.968). Variceal rebleeding occurred during follow-up in 12 (36.4%) and 11 (35.5%) patients in the carvedilol and VBL groups, respectively (p=0.857), with 9 (27.3%) and 16 (51.6%) deaths in each group, respectively (p=0.110)., Conclusions: Carvedilol is not superior to VBL in the prevention of variceal rebleeding. The trend to a survival benefit for patients taking this drug compared with those undergoing banding requires further exploration., (Copyright © 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Inhibition of histone deacetylase 6 (HDAC6)-dependent aggresome function by pan HDAC inhibitors was recently reported to be a key mechanism underlying the synergistic activity between proteasome inhibitors and HDAC inhibitors in a variety of tumour types. Because these combinations induce significant thrombocytopenia in vivo, we examined whether less toxic, isotype-selective HDAC inhibitors may still synergize with proteasome inhibitors, and if so, by what mechanisms. Here, we showed that the class I HDAC inhibitor, MGCD0103, has a potent antiproliferative activity in Hodgkin lymphoma (HL) cell lines. Furthermore, MGCD0103 induced tumour necrosis factor α (TNF-α) expression and secretion, which was associated with nuclear factor (NF)-κB activation. Selective inhibition of TNF-α expression by short interfering mRNA, or inhibition of MGCD0103-induced NF-kB activation by proteasome inhibitors enhanced MGCD0103-induced cell death. Thus, our results demonstrate that MGCD0103 may synergize with proteasome inhibitors by HDAC6-independent mechanisms, providing mechanistic rationale for exploring this potentially less toxic combination for the treatment of lymphoma., (© 2010 Blackwell Publishing Ltd.)

Background: Transjugular intrahepatic portosystemic stent-shunt (TIPSS) is increasingly used for the management of portal hypertension. We report on 10 years' experience at a single centre., Methods: Data held in a dedicated database was retrieved on 497 patients referred for TIPSS. The efficacy of TIPSS and its complications were assessed., Results: Most patients were male (59.4%) with alcoholic liver disease (63.6%), and bleeding varices (86.8%). Technical success was achieved in 474 (95.4%) patients. A total of 13.4% of patients bled at portal pressure gradients < or = 12 mmHg, principally from gastric and ectopic varices. Procedure-related mortality was 1.2%. The mean follow-up period of surviving patients was 33.3 +/- 1.9 months. Primary shunt patency rates were 45.4% and 26.0% at 1 and 2 years, respectively, while the overall secondary assisted patency rate was 72.2%. Variceal rebleeding rate was 13.7%, with all episodes occurring within 2 years of TIPSS insertion, and almost all due to shunt dysfunction. The overall mortality rate was 60.4%, mainly resulting from end-stage liver failure (42.5%). Patients who bled from gastric varices had lower mortality than those from oesophageal varices (53.9% versus 61.5%, P < 0.01). The overall rate of hepatic encephalopathy was 29.9% (de novo encephalopathy was 11.5%), with pre-TIPSS encephalopathy being an independent predicting variable. Refractory ascites responded to TIPSS in 72% of cases, although the incidence of encephalopathy was high in this group (36.0%)., Conclusions: TIPSS is effective in the management of variceal bleeding, and has a low complication rate. With surveillance, good patency can be achieved. Careful selection of patients is needed to reduce the encephalopathy rate.

Leishmaniaviruses (LRV) are double-stranded RNA viruses that persistently infect some strains of the protozoan parasite Leishmania. The identification of a short viral RNA transcript led to our discovery of an endoribonuclease activity of the LRV capsid protein. Other known endoribonucleases serve a variety of diverse roles in the regulated balance of processing and degradation of both cellular and viral RNAs, thus determining the amount and functionality of specific RNA molecules in a cell at any given time. The consequence of LRV RNA cleavage on the LRV life cycle has not yet been determined. Here we review the LRV endoribonuclease and discuss potential roles for this endoribonuclease activity in the context of the involvement of other endoribonucleases in regulating viral gene expression and replicative capacity.