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Coordinated Regulation of Cap-Dependent Translation and MicroRNA Function by Convergent Signaling Pathways [Articles]

Abstract: Cell growth and proliferation require the coordinated activation of many cellular processes, including cap-dependent mRNA translation. MicroRNAs oppose cap-dependent translation and set thresholds for expression of target proteins. Emerging data suggest that microRNA function is enhanced by cellular activation due in part to induction of the RNA-induced silencing complex (RISC) scaffold protein GW182. In the current study, we demonstrate that increased expression of GW182 in activated or transformed immune cells results from effects of phosphoinositol 3-kinase–Akt–mechanistic target of rapamycin (PI3K-Akt-mTOR) and Jak-Stat-Pim signaling on the translation of GW182 mRNA. Both signaling pathways enhanced polysome occupancy and eukaryotic initiation factor 4E (eIF4E) binding to the 5' 7mG cap of GW182 mRNA. The effect of Jak-Stat-Pim signaling on polysome occupancy and expression of GW182 protein was greater than that of PI3K-Akt-mTOR signaling, likely resulting from enhanced eIF4A-dependent unwinding of G-quadruplexes in the 5' untranslated region of GW182 mRNA. Consistent with this, GW182 expression and microRNA function were reduced by inhibition of mTOR or Pim kinases, translation initiation complex assembly, or eIF4A function. Taken together, these data provide a mechanistic link between microRNA function and cap-dependent translation that allows activated immune cells to maintain microRNA-mediated repression of targets despite enhanced rates of protein synthesis.

Pub.: 26 Aug '16, Pinned: 29 Sep '16

Argonaute Family Protein Expression in Normal Tissue and Cancer Entities.

Abstract: The members of the Argonaute (AGO) protein family are key players in miRNA-guided gene silencing. They enable the interaction between small RNAs and their respective target mRNA(s) and support the catalytic destruction of the gene transcript or recruit additional proteins for downstream gene silencing. The human AGO family consists of four AGO proteins (AGO1-AGO4), but only AGO2 harbors nuclease activity. In this study, we characterized the expression of the four AGO proteins in cancer cell lines and normal tissues with a new mass spectrometry approach called AGO-APP (AGO Affinity Purification by Peptides). In all analyzed normal tissues, AGO1 and AGO2 were most prominent, but marked tissue-specific differences were identified. Furthermore, considerable changes during development were observed by comparing fetal and adult tissues. We also identified decreased overall AGO expression in melanoma derived cell lines compared to other tumor cell lines and normal tissues, with the largest differences in AGO2 expression. The experiments described in this study suggest that reduced amounts of AGO proteins, as key players in miRNA processing, have impact on several cellular processes. Deregulated miRNA expression has been attributed to chromosomal aberrations, promoter regulation and it is known to have a major impact on tumor development and progression. Our findings will further increase our basic understanding of the molecular basis of miRNA processing and its relevance for disease.

Pub.: 16 Aug '16, Pinned: 29 Sep '16

NKAIN2 functions as a novel tumor suppressor in prostate cancer.

Abstract: Recurrent chromosome breakpoints at 6q22.31, leading to truncation and potential loss-of-function of the NKAIN2 gene, in Chinese prostate cancer patients were previously identified. In this study we investigated genomic, methylation and expression changes of NKAIN2 in a large number of prostate cancer samples and determined its functional role in prostate cancer cells. Fluorescence in situ hybridization analysis confirmed that NKAIN2 truncation is specific to Chinese while deletion of the gene is frequent in both Chinese and UK prostate cancers. Significantly reduced expression of NKAIN2 was also detected at both RNA and protein levels. Somatic mutations of NKAIN2 in prostate cancer samples exist but at very low frequency, suggesting that it is a putative tumor suppressor gene (TSG) with haploid insufficiency. Our functional studies showed that overexpression of NKAIN2 in prostate cancer cells inhibits cellular growth by promoting cell apoptosis, and decreasing cell migration and invasion. Conversely, knockdown of NKAIN2 promotes prostate cancer cell growth by inhibiting cell apoptosis, and increasing cell migration and invasion. These data imply that NKAIN2 is a novel TSG whose activity is commonly reduced in prostate cancer. It may restrain the disease development and progression by inducing apoptosis and suppressing cancer cell growth, migration and invasion. This study provides new insights into prostate carcinogenesis and opportunities for development of novel therapies for prostate cancer.

Pub.: 03 Sep '16, Pinned: 21 Sep '16

Oncolytic adenovirus-mediated therapy for prostate cancer.

Abstract: Prostate cancer is a leading cause of cancer-related death and morbidity in men in the Western world. Tumor progression is dependent on functioning androgen receptor signaling, and initial administration of antiandrogens and hormone therapy (androgen-deprivation therapy) prevent growth and spread. Tumors frequently develop escape mechanisms to androgen-deprivation therapy and progress to castration-resistant late-stage metastatic disease that, in turn, inevitably leads to resistance to all current therapeutics, including chemotherapy. In spite of the recent development of more effective inhibitors of androgen-androgen receptor signaling such as enzalutamide and abiraterone, patient survival benefits are still limited. Oncolytic adenoviruses have proven efficacy in prostate cancer cells and cause regression of tumors in preclinical models of numerous drug-resistant cancers. Data from clinical trials demonstrate that adenoviral mutants have limited toxicity to normal tissues and are safe when administered to patients with various solid cancers, including prostate cancer. While efficacy in response to adenovirus administration alone is marginal, findings from early-phase trials targeting local-ized and metastatic prostate cancer suggest improved efficacy in combination with cytotoxic drugs and radiation therapy. Here, we review recent progress in the development of multimodal oncolytic adenoviruses as biological therapeutics to improve on tumor elimination in prostate cancer patients. These optimized mutants target cancer cells by several mechanisms including viral lysis and by expression of cytotoxic transgenes and immune-stimulatory factors that activate the host immune system to destroy both infected and noninfected prostate cancer cells. Additional modifications of the viral capsid proteins may support future systemic delivery of oncolytic adenoviruses.

Pub.: 01 Sep '16, Pinned: 21 Sep '16

Expression of polycomb protein BMI-1 maintains the plasticity of basal bronchial epithelial cells.

Abstract: The airway epithelium is altered in respiratory disease and is thought to contribute to disease etiology. A caveat to disease research is that the technique of isolation of bronchial epithelial cells from patients is invasive and cells have a limited lifespan. The aim of this study was to extensively characterize the plasticity of primary human bronchial epithelial cells that have been engineered to delay cell senescence including the ability of these cells to differentiate. Cells were engineered to express BMI-1 or hTERT using viral vector systems. Cells were characterized at passage (p) early (p5), mid (p10), and late (p15) stage for: BMI-1, p16, and CK14 protein expression, viability and the ability to differentiate at air-liquid interface (ALI), using a range of techniques including immunohistochemistry (IHC), immunofluorescence (IF), transepithelial electrical resistance (TEER), scanning electron microscopy (SEM), MUC5AC and beta tubulin (BTUB) staining. BMI-1-expressing cells maintained elevated levels of the BMI-1 protein and the epithelial marker CK14 and showed a suppression of p16. BMI-1-expressing cells had a viability advantage, differentiated at ALI, and had a normal karyotype. In contrast, hTERT-expressing cells had a reduced viability, showed limited differentiation, and had an abnormal karyotype. We therefore provide extensive characterization of the plasticity of BMI-1 expressing cells in the context of the ALI model. These cells retain properties of wild-type cells and may be useful to characterize respiratory disease mechanisms in vitro over sustained periods.

Pub.: 26 Aug '16, Pinned: 21 Sep '16

CRISPR/Cas9-mediated Trp53 and Brca2 knockout to generate improved murine models of ovarian high grade serous carcinoma.

Abstract: There is a need for transplantable murine models of ovarian high grade serous carcinoma (HGSC) with regard to mutations in the human disease, to assist investigations of the relationships between tumor genotype, chemotherapy response and immune microenvironment. In addressing this need, we performed whole exome sequencing of ID8, the most widely-used transplantable model of ovarian cancer, covering 194,000 exomes at a mean depth of 400x with 90% exons sequenced >50x. We found no functional mutations in genes characteristic of HGSC (Trp53, Brca1, Brca2, Nf1, Rb1) and p53 remained transcriptionally active. Homologous recombination in ID8 remained intact in functional assays. Further, we found no mutations typical of clear cell carcinoma (Arid1A, Pik3ca), low grade serous carcinoma (Braf), endometrioid (Ctnnb1) or mucinous (Kras) carcinomas. Using CRISPR/Cas9 gene editing, we modeled HGSC by generating novel ID8 derivatives that harbored single (Trp53-/-) or double (Trp53-/-;Brca2-/-) suppressor gene deletions. In these mutants, loss of p53 alone was sufficient to increase the growth rate of orthotopic tumors with significant effects observed on the immune microenvironment. Specifically, p53 loss increased expression of the myeloid attractant CCL and promoted the infiltration of immunosuppressive myeloid cell populations into primary tumors and their ascites. In Trp53-/-;Brca2-/- mutant cells, we documented a relative increase in sensitivity to the PARP inhibitor rucaparib and slower orthotopic tumor growth compared to Trp53-/- cells, with an appearance of intra-tumoral tertiary lymphoid structures rich in CD3+ T cells. This work validates new CRISPR-generated models of HGSC to investigate its biology and promote mechanism-based therapeutics discovery.

Pub.: 18 Aug '16, Pinned: 21 Sep '16

The efficacy of oncolytic adenovirus is mediated by T cell responses against virus and tumor in Syrian hamster model.

Abstract: Purpose:Oncolytic adenoviruses (Ad) represent an innovative approach to cancer therapy. Its efficacy depends on multiple actions including direct tumor lysis, stimulation of antiviral and antitumor immune responses. In this study, we investigated the roles of T cell responses in oncolytic adenoviral therapy.An immunocompetent and viral replication-permissive Syrian hamster tumor model was used. The therapeutic mechanisms of oncolytic Ad were investigated by T-cell deletion, immunohistochemistry staining, and CTL assay.Deletion of T cells with an anti-CD3 antibody completely demolished the antitumor efficacy of oncolytic Ad. Intratumoral injection of Ad induced strong virus- and tumor-specific T cell responses, as well as antiviral antibody response. Both anti-viral and anti-tumor T cell responses contributed to the efficacy of oncolytic Ad. Deletion of T cells increased viral replication and extended the persistence of infectious virus within tumors, but almost abrogated the antitumor efficacy. Preexisting antiviral immunity promoted the clearance of injected oncolytic Ad from tumors, but had no effect on antitumor efficacy. Strikingly, the repeated treatment with oncolytic Ad has strong therapeutic effect on relapsed tumors or tumors insensitive to the primary viral therapy.These results demonstrate that T cell-mediated immune responses outweigh the direct oncolysis in mediating antitumor efficacy of oncolytic Ad. Our data has a high impact on redesigning the regimen of oncolytic adenovirus for cancer treatment.

Pub.: 21 Jul '16, Pinned: 21 Sep '16

Neoadjuvant Chemotherapy Modulates the Immune Microenvironment in Metastases of Tubo-Ovarian High-Grade Serous Carcinoma.

Abstract: The purpose of this study was to assess the effect of neoadjuvant chemotherapy (NACT) on immune activation in stage IIIC/IV tubo-ovarian high-grade serous carcinoma (HGSC), and its relationship to treatment response.We obtained pre- and posttreatment omental biopsies and blood samples from a total of 54 patients undergoing platinum-based NACT and 6 patients undergoing primary debulking surgery. We measured T-cell density and phenotype, immune activation, and markers of cancer-related inflammation using IHC, flow cytometry, electrochemiluminescence assays, and RNA sequencing and related our findings to the histopathologic treatment response.There was evidence of T-cell activation in omental biopsies after NACT: CD4(+) T cells showed enhanced IFNγ production and antitumor Th1 gene signatures were increased. T-cell activation was more pronounced with good response to NACT. The CD8(+) T-cell and CD45RO(+) memory cell density in the tumor microenvironment was unchanged after NACT but biopsies showing a good therapeutic response had significantly fewer FoxP3(+) T regulatory (Treg) cells. This finding was supported by a reduction in a Treg cell gene signature in post- versus pre-NACT samples that was more pronounced in good responders. Plasma levels of proinflammatory cytokines decreased in all patients after NACT. However, a high proportion of T cells in biopsies expressed immune checkpoint molecules PD-1 and CTLA4, and PD-L1 levels were significantly increased after NACT.NACT may enhance host immune response but this effect is tempered by high/increased levels of PD-1, CTLA4, and PD-L1. Sequential chemoimmunotherapy may improve disease control in advanced HGSC. Clin Cancer Res; 22(12); 3025-36. ©2016 AACR.

Pub.: 17 Jun '16, Pinned: 21 Sep '16

Reduced expression of histone methyltransferases KMT2C and KMT2D correlates with improved outcome in pancreatic ductal adenocarcinoma.

Abstract: Genes encoding the histone H3 lysine 4 methyltransferases KMT2C and KMT2D are subject to deletion and mutation in pancreatic ductal adenocarcinoma (PDAC), where these lesions identify a group of patients with a more favorable prognosis. In this study, we demonstrate that low KMT2C and KMT2D expression in biopsies also defines better outcome groups, with median survivals of 15.9 vs 9.2 months (p = 0.029), and 19.9 vs 11.8 months (p = 0.001) respectively. Experiments with eight human pancreatic cell lines showed attenuated cell proliferation when these methyltransferases were depleted, suggesting that this improved outcome may reflect a cell-cycle block with diminished progression from G0/G1. RNA-seq analysis of PDAC cell lines following KMT2C or KMT2D knockdown, identified 31 and 124 differentially expressed genes respectively, with 19 genes in common. Gene set enrichment analysis revealed significant downregulation of genes related to cell-cycle and growth. These data were corroborated independently by examining KMT2C/D signatures extracted from the International Cancer Genome Consortium and The Cancer Genome Atlas datasets. Furthermore, these experiments highlighted a potential role for NCAPD3, a condensin II complex subunit, as an outcome predictor in PDAC using existing gene expression series. Kmt2d depletion in KC/KPC cell lines also led to an increased response to the nucleoside analogue 5-fluorouracil, suggesting that lower levels of this methyltransferase may mediate the sensitivity of PDAC to particular treatments. Therefore, it may also be therapeutically beneficial to target these methyltransferases in PDAC, especially in those patients demonstrating higher KTM2C/D expression.

Pub.: 10 Jun '16, Pinned: 21 Sep '16

Localized irradiation of cell membrane by Auger electrons is cytotoxic through oxidative stress-mediated non-targeted effects.

Abstract: We investigated whether radiation-induced non-targeted effects are involved in the cytotoxic effects of anti-cell surface monoclonal antibodies labeled with Auger electron emitters, such as iodine 125 (<sup>125</sup>I-mAbs).We showed that non-targeted effects are mainly responsible for the cytotoxicity of <sup>125</sup>I-mAbs targeting the cell membrane of p53<sup>+/+ </sup>HCT116 colon cancer cells. Targeted and non-targeted cytotoxicity were inhibited in vitro following lipid raft disruption with Methyl-β-cyclodextrin (MBCD) or filipin or use of radical oxygen species scavengers. <sup>125</sup>I-mAb efficacy was associated with acid sphingomyelinase activation and modulated through activation of the AKT, ERK1/2, p38 kinase, JNK signaling pathways, and also of phospholipase C-Υ (PLC-Υ), proline-rich tyrosine kinase 2 (PYK-2) and paxillin, involved in Ca<sup>2+</sup> fluxes. Moreover, the non-targeted response induced by directing 5-[(125)I]iodo-2'-deoxyuridine to the nucleus was comparable to that of <sup>125</sup>I-mAbs against cell surface receptors. In vivo, we found that the statistical significance of tumor growth delay induced by <sup>125</sup>I-mAbs was removed after MBCD treatment and observed oxidative DNA damage beyond the expected Auger electron range. These results suggest the involvement of non-targeted effects also in vivo.Low energy Auger electrons, such as those emitted by iodine 125, have a short tissue range and are targeted to the nucleus to maximize their cytotoxicity. Here, we show that targeting the cancer cell surface with <sup>125</sup>I-mAbs produces a lipid raft-mediated non-targeted response that compensate for the inferior efficacy of non-nuclear targeting.Our findings describe the mechanisms involved in the efficacy of <sup>125</sup>I-mAbs targeting the cancer cell surface.

Pub.: 26 May '16, Pinned: 21 Sep '16

SEARCHBreast: a new resource to locate and share surplus archival material from breast cancer animal models to help address the 3Rs.

Abstract: Animal models have contributed to our understanding of breast cancer, with publication of results in high-impact journals almost invariably requiring extensive in vivo experimentation. As such, many laboratories hold large collections of surplus animal material, with only a fraction being used in publications relating to the original projects. Despite being developed at considerable cost, this material is an invisible and hence an underutilised resource, which often ends up being discarded. Within the breast cancer research community there is both a need and desire to make this valuable material available for researchers. Lack of a coordinated system for visualisation and localisation of this has prevented progress. To fulfil this unmet need, we have developed a novel initiative called Sharing Experimental Animal Resources: Coordinating Holdings-Breast (SEARCHBreast) which facilitates sharing of archival tissue between researchers on a collaborative basis and, de facto will reduce overall usage of animal models in breast cancer research. A secure searchable database has been developed where researchers can find, share, or upload materials related to animal models of breast cancer, including genetic and transplant models. SEARCHBreast is a virtual compendium where the physical material remains with the original laboratory. A bioanalysis pipeline is being developed for the analysis of transcriptomics data associated with mouse models, allowing comparative study with human and cell line data. Additionally, SEARCHBreast is committed to promoting the use of humanised breast tissue models as replacement alternatives to animals. Access to this unique resource is freely available to all academic researchers following registration at https://searchbreast.org .

Pub.: 17 Apr '16, Pinned: 21 Sep '16

The role of new PET tracers for lung cancer.

Abstract: 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) is established for characterising indeterminate pulmonary nodules and staging lung cancer where there is curative intent. Whilst a sensitive technique, specificity for characterising lung cancer is limited. There is recognition that evaluation of other aspects of abnormal cancer biology in addition to glucose metabolism may be more helpful in characterising tumours and predicting response to novel targeted cancer therapeutics. Therefore, efforts have been made to develop and evaluate new radiopharmaceuticals in order to improve the sensitivity and specificity of PET imaging in lung cancer with regards to characterisation, treatment stratification and therapeutic monitoring. 18F-fluorothymidine (18F-FLT) is a marker of cellular proliferation. It shows a lower accumulation in tumours than 18F-FDG as it only accumulates in the cells that are in the S phase of growth and demonstrates a low sensitivity for nodal staging. Its main role is in evaluating treatment response. Methionine is an essential amino acid. 11C-methionine is more specific and sensitive than 18F-FDG in differentiating benign and malignant thoracic nodules. 18Ffluoromisonidazole (18F-FMISO) is used for imaging tumour hypoxia. Tumour response to treatment is significantly related to the level of tumour oxygenation. Angiogenesis is the process by which new blood vessels are formed in tumours and is involved in tumour growth and metastatic tumour spread and is a therapeutic target. Most clinical studies have focused on targeted integrin PET imaging of which αvβ3 integrin is the most extensively investigated. It is upregulated on activated endothelial cells in association with tumour angiogenesis. Neuroendocrine tumour tracers, particularly 68Ga-DOTA-peptides, have an established role in imaging of carcinoid tumours. Whilst most of these tracers have predominantly been used in the research environment, they offer exciting opportunities for improving staging, characterisation, stratification and response assessment in an era of increased personalised therapy in lung cancer.

Pub.: 15 Mar '16, Pinned: 21 Sep '16

A genetic study and meta-analysis of the genetic predisposition of prostate cancer in a Chinese population.

Abstract: Prostate cancer predisposition has been extensively investigated in European populations, but there have been few studies of other ethnic groups. To investigate prostate cancer susceptibility in the under-investigated Chinese population, we performed single-nucleotide polymorphism (SNP) array analysis on a cohort of Chinese cases and controls and then meta-analysis with data from the existing Chinese prostate cancer genome-wide association study (GWAS). Genotyping 211,155 SNPs in 495 cases and 640 controls of Chinese ancestry identified several new suggestive Chinese prostate cancer predisposition loci. However, none of them reached genome-wide significance level either by meta-analysis or replication study. The meta-analysis with the Chinese GWAS data revealed that four 8q24 loci are the main contributors to Chinese prostate cancer risk and the risk alleles from three of them exist at much higher frequencies in Chinese than European populations. We also found that several predisposition loci reported in Western populations have different effect on Chinese men. Therefore, this first extensive single-nucleotide polymorphism study of Chinese prostate cancer in comparison with European population indicates that four loci on 8q24 contribute to a great risk of prostate cancer in a considerable large proportion of Chinese men. Based on those four loci, the top 10% of the population have six- or two-fold prostate cancer risk compared with men of the bottom 10% or median risk respectively, which may facilitate the design of prostate cancer genetic risk screening and prevention in Chinese men. These findings also provide additional insights into the etiology and pathogenesis of prostate cancer.

Pub.: 18 Feb '16, Pinned: 21 Sep '16

The E1B19K-deleted oncolytic adenovirus mutant AdΔ19K sensitizes pancreatic cancer cells to drug-induced DNA-damage by down-regulating Claspin and Mre11.

Abstract: Adenovirus-mediated sensitization of cancer cells to cytotoxic drugs depends on simultaneous interactions of early viral genes with cell death and survival pathways. It is unclear what cellular factors mediate these interactions in the presence of DNA-damaging drugs. We found that adenovirus prevents Chk1-mediated checkpoint activation through inactivation of Mre11 and downregulation of the pChk1 adaptor-protein, Claspin, in cells with high levels of DNA-damage induced by the cytotoxic drugs gemcitabine and irinotecan. The mechanisms for Claspin downregulation involve decreased transcription and increased degradation, further attenuating pChk1-mediated signalling. Live cell imaging demonstrated that low doses of gemcitabine caused multiple mitotic aberrations including multipolar spindles, micro- and multi-nucleation and cytokinesis failure. A mutant virus with the anti-apoptotic E1B19K-gene deleted (AdΔ19K) further enhanced cell killing, Claspin downregulation, and potentiated drug-induced DNA damage and mitotic aberrations. Decreased Claspin expression and inactivation of Mre11 contributed to the enhanced cell killing in combination with DNA-damaging drugs. These results reveal novel mechanisms that are utilised by adenovirus to ensure completion of its life cycle in the presence of cellular DNA damage. Taken together, our findings reveal novel cellular targets that may be exploited when developing improved anti-cancer therapeutics.

Pub.: 13 Feb '16, Pinned: 21 Sep '16