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We previously observed increased levels of adenosine‐deaminase‐acting‐on‐dsRNA (Adar)‐dependent RNA editing during mesothelioma development in mice exposed to asbestos. The aim of this study was to characterize and assess the role of ADAR‐dependent RNA editing in mesothelioma. We found that tumors and mesothelioma primary cultures have higher ADAR‐mediated RNA editing compared to mesothelial cells. Unsupervised clustering of editing in different genomic regions revealed heterogeneity between tumor samples as well as mesothelioma primary cultures. ADAR2 expression levels are higher in BRCA1‐associated protein 1 wild‐type tumors, with corresponding changes in RNA editing in transcripts and 3'UTR. ADAR2 knockdown and rescue models indicated a role in cell proliferation, altered cell cycle, increased sensitivity to antifolate treatment, and type‐1 interferon signaling upregulation, leading to changes in the microenvironment in vivo. Our data indicate that RNA editing contributes to mesothelioma heterogeneity and highlights an important role of ADAR2 not only in growth regulation in mesothelioma but also in chemotherapy response, in addition to regulating inflammatory response downstream of sensing nucleic acid structures. [ABSTRACT FROM AUTHOR]

Mesothelioma affects mostly older individuals who have been occupationally exposed to asbestos. The global mesothelioma incidence and mortality rates are unknown, because data are not available from developing countries that continue to use large amounts of asbestos. The incidence rate of mesothelioma has decreased in Australia, the United States, and Western Europe, where the use of asbestos was banned or strictly regulated in the 1970s and 1980s, demonstrating the value of these preventive measures. However, in these same countries, the overall number of deaths from mesothelioma has not decreased as the size of the population and the percentage of old people have increased. Moreover, hotspots of mesothelioma may occur when carcinogenic fibers that are present in the environment are disturbed as rural areas are being developed. Novel immunohistochemical and molecular markers have improved the accuracy of diagnosis; however, about 14% (high-resource countries) to 50% (developing countries) of mesothelioma diagnoses are incorrect, resulting in inadequate treatment and complicating epidemiological studies. The discovery that germline BRCA1-asssociated protein 1 (BAP1) mutations cause mesothelioma and other cancers (BAP1 cancer syndrome) elucidated some of the key pathogenic mechanisms, and treatments targeting these molecular mechanisms and/or modulating the immune response are being tested. The role of surgery in pleural mesothelioma is controversial as it is difficult to predict who will benefit from aggressive management, even when local therapies are added to existing or novel systemic treatments. Treatment outcomes are improving, however, for peritoneal mesothelioma. Multidisciplinary international collaboration will be necessary to improve prevention, early detection, and treatment. [ABSTRACT FROM AUTHOR]

Introduction Alterations of the tumor suppressor Neurofibromatosis type II ( NF2 ) have been reported in about 40% of Malignant pleural mesothelioma (MPM) patients. NF2 (Merlin) deficiency leads to alterations of the Hippo pathway; resulting in activation of the oncogenic Yes Associated Protein-1 (YAP1). Our aim was to investigate the association between these alterations and clinical outcomes. Material and methods Tissue microarrays composed of MPM tumors derived from 2 independent MPM cohorts were employed for this study. Immunohistochemical expression of Merlin, YAP1 and its target genes, Survivin and connective tissue growth factor (CTGF) were assessed in nuclear and cytoplasmic fractions. Cohort 1 was comprised of 145 patients intended to be treated with chemotherapy (CTX) followed by extrapleural pneumonectomy (EPP), thus both pre- and post-CTX tissues were available. Cohort 2 was comprised of 59 patients treated with EPP followed by intraoperative hyperthermic cisplatin and/or adjuvant CTX and/or radiotherapy. Marker expression was quantified by means of labeling index (%) for nuclear Survivin and by H-score for the other markers. The dichotomized marker expression was tested for the association with overall survival (OS) and freedom from recurrence (FFR). Results Kaplan–Meier survival curves revealed a significant association between low cytoplasmic Merlin expression in pre-induction CTX tissues of cohort 1 with shorter FFR (p = 0.02) and OS (p = 0.03). The same tendency was observed in the chemotherapy naïve tissues obtained during EPP of cohort 2. Low nuclear Merlin expression in post-CTX tissues (available from cohort 1 only) was associated with shorter FFR (p = 0.04) and OS (p = 0.05). High nuclear Survivin labeling indices in both pre- and post-CTX tissues of cohort 1 was associated with shorter FFR (p = 0.02). In cohort 2, this was associated with both FFR and OS (p = 0.046 and p = 0.002, respectively). In multivariate analysis, low expression of cytoplasmic Merlin remained an independent prognosticator for shorter FFR of cohort 1 [hazard ratio (HR) = 0.5, 95% confidence interval (CI) = 0.3–0.9, p = 0.001] and OS [HR = 0.5, 95% CI = 0.3–1, p = 0.04]. High Survivin labeling index was an independent prognostic factor for shorter FFR in patients from cohort 1 [HR = 3.4, 95% CI = 1.7–6.8, p = 0.006] and shorter OS in patients from cohort 2 [HR = 2.35, 95% CI = 1.27–4.33, p = 0.006]. Conclusions Our findings uncover the significance of Merlin protein expression and Survivin labeling index as prognosticators for poor clinical outcome in two independent MPM cohorts. If confirmed, these markers may be used to identify subgroups of patients benefitting from additional treatment. [ABSTRACT FROM AUTHOR]

REV3, the catalytic subunit of translesion polymerase zeta (polζ), is commonly associated with DNA damage bypass and repair. Despite sharing accessory subunits with replicative polymerase δ, very little is known about the role of polζ in DNA replication. We previously demonstrated that inhibition of REV3 expression induces persistent DNA damage and growth arrest in cancer cells. To reveal determinants of this sensitivity and obtain insights into the cellular function of REV3, we performed whole human genome RNAi library screens aimed at identification of synthetic lethal interactions with REV3 in A549 lung cancer cells. The top confirmed hit was RRM1, the large subunit of ribonucleotide reductase (RNR), a critical enzyme of de novo nucleotide synthesis. Treatment with the RNR-inhibitor hydroxyurea (HU) synergistically increased the fraction of REV3-deficient cells containing single stranded DNA (ssDNA) as indicated by an increase in replication protein A (RPA). However, this increase was not accompanied by accumulation of the DNA damage marker γH2AX suggesting a role of REV3 in counteracting HU-induced replication stress (RS). Consistent with a role of REV3 in DNA replication, increased RPA staining was confined to HU-treated S-phase cells. Additionally, we found genes related to RS to be significantly enriched among the top hits of the synthetic sickness/lethality (SSL) screen further corroborating the importance of REV3 for DNA replication under conditions of RS. [ABSTRACT FROM AUTHOR]

Inducible nitric oxide synthase (iNOS) functions as a homodimer. In cell extracts, iNOS molecules partition both in cytosolic and particulate fractions, indicating that iNOS exists as soluble and membrane associated forms. In this study, iNOS features were investigated in human intestinal epithelial cells stimulated with cytokines and in duodenum from mice exposed to flagellin. Our experiments indicate that iNOS is mainly associated with the particulate fraction of cell extracts. Confocal microscopy showed a preferential localization of iNOS at the apical pole of intestinal epithelial cells. In particulate fractions, iNOS dimers were more abundant than in the cytosolic fraction. Similar observations were seen in mouse duodenum samples. These results suggest that, in epithelial cells, iNOS activity is regulated by localization-dependent processes. [ABSTRACT FROM AUTHOR]

To investigate the influence of glutathione (GSH) on cellular effects of nitric oxide (NO) formation, human colon adenocarcinoma cells were transfected with a vector allowing controlled expression of inducible nitric oxide synthase (iNOS). Protein levels of oxidative stress-sensitive heme oxygenase-1 (HO-1) were analyzed in the presence or absence of GSH depletion using L-buthionine-[S,R]-sulfoximine and iNOS induction. While no effect was observed in the presence of iNOS activity alone, a synergistic effect on HO-1 expression was observed in the presence of iNOS expression and GSH depletion. This effect was prevented by addition of N-methyl-L-arginine. Therefore, targeting of endogenous NO may be modulated by intracellular GSH. [Copyright &y& Elsevier]