Publications by authors named "Alexander Greenhough"

28 Publications

  • Page 1 of 1

Interacting Proteins, Polymorphisms and the Susceptibility of Animals to SARS-CoV-2.

Animals (Basel) 2021 Mar 12;11(3). Epub 2021 Mar 12.

Department of Applied Sciences, University of the West of England, Bristol BS16 1QY, UK.

COVID-19, caused by SARS-CoV-2, is a world-wide problem for the human population. It is known that some animal species, such as mink, can become infected and transmit the virus. However, the susceptibility of most animals is not known. Here, we review the use of sequence analysis of the proteins which are known to interact with SARS-CoV-2 as a way to estimate an animal's susceptibility. Although most such work concentrates on the angiotensin-converting enzyme 2 receptor (ACE2), here TMPRSS2 (Transmembrane Serine Protease 2), neuropilin-1 and furin are also considered. Polymorphisms, especially ones which are known to alter viral/host interactions are also discussed. Analysis of ACE2 and TMPRSS2 protein sequences across species suggests this approach may be of some utility in predicting susceptibility; however, this analysis fails to highlight some susceptible animals such as mink. However, combined with observational data which emerges over time about which animals actually become infected, this may, in the future, be a useful tool to assist the management of risks associated with human/animal contact and support conservation and animal welfare measures.
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http://dx.doi.org/10.3390/ani11030797DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8000148PMC
March 2021

5-Aminosalicylic acid inhibits stem cell function in human adenoma-derived cells: implications for chemoprophylaxis in colorectal tumorigenesis.

Br J Cancer 2021 Jun 30;124(12):1959-1969. Epub 2021 Mar 30.

Cellular and Molecular Medicine, Biomedical Sciences Building, University of Bristol, Bristol, BS8 1TD, UK.

Background: Most colorectal cancers (CRC) arise sporadically from precursor lesions: colonic polyps. Polyp resection prevents progression to CRC. Risk of future polyps is proportional to the number and size of polyps detected at screening, allowing identification of high-risk individuals who may benefit from effective chemoprophylaxis. We aimed to investigate the potential of 5-aminosalicylic acid (5-ASA), a medication used in the treatment of ulcerative colitis, as a possible preventative agent for sporadic CRC.

Methods: Human colorectal adenoma (PC/AA/C1, S/AN/C1 and S/RG/C2), transformed adenoma PC/AA/C1/SB10 and carcinoma cell lines (LS174T and SW620) were treated with 5-ASA. The effect on growth in two- and three-dimensional (3D) culture, β-catenin transcriptional activity and on cancer stemness properties of the cells were investigated.

Results: 5-ASA was shown, in vitro, to inhibit the growth of adenoma cells and suppress β-catenin transcriptional activity. Downregulation of β-catenin was found to repress expression of stem cell marker LGR5 (leucine-rich G protein-coupled receptor-5) and functionally suppress stemness in human adenoma and carcinoma cells using 3D models of tumorigenesis.

Conclusions: 5-ASA can suppress the cancer stem phenotype in adenoma-derived cells. Affordable and well-tolerated, 5-ASA is an outstanding candidate as a chemoprophylactic medication to reduce the risk of colorectal polyps and CRC in those at high risk.
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http://dx.doi.org/10.1038/s41416-021-01354-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8184823PMC
June 2021

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition).

Autophagy 2021 Jan 8;17(1):1-382. Epub 2021 Feb 8.

University of Crete, School of Medicine, Laboratory of Clinical Microbiology and Microbial Pathogenesis, Voutes, Heraklion, Crete, Greece; Foundation for Research and Technology, Institute of Molecular Biology and Biotechnology (IMBB), Heraklion, Crete, Greece.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.
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http://dx.doi.org/10.1080/15548627.2020.1797280DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7996087PMC
January 2021

Transcriptomic Analyses of MYCN-Regulated Genes in Anaplastic Wilms' Tumour Cell Lines Reveals Oncogenic Pathways and Potential Therapeutic Vulnerabilities.

Cancers (Basel) 2021 Feb 6;13(4). Epub 2021 Feb 6.

Cancer Epigenetics Laboratory, School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK.

The proto-oncogene is deregulated in many cancers, most notably in neuroblastoma, where gene amplification identifies a clinical subset with very poor prognosis. Gene expression and DNA analyses have also demonstrated overexpression of mRNA, as well as focal amplifications, copy number gains and presumptive change of function mutations of in Wilms' tumours with poorer outcomes, including tumours with diffuse anaplasia. Surprisingly, however, the expression and functions of the MYCN protein in Wilms' tumours still remain obscure. In this study, we assessed MYCN protein expression in primary Wilms' tumours using immunohistochemistry of tissue microarrays. We found MYCN protein to be expressed in tumour blastemal cells, and absent in stromal and epithelial components. For functional studies, we used two anaplastic Wilms' tumour cell-lines, WiT49 and 17.94, to study the biological and transcriptomic effects of MYCN depletion. We found that MYCN knockdown consistently led to growth suppression but not cell death. RNA sequencing identified 561 MYCN-regulated genes shared by WiT49 and 17.94 cell-lines. As expected, numerous cellular processes were downstream of MYCN. MYCN positively regulated the miRNA regulator and known Wilms' tumour oncogene , the genes encoding methylosome proteins PRMT1, PRMT5 and WDR77, and the mitochondrial translocase genes and . MYCN repressed genes including the developmental signalling receptor and the stromal marker . Importantly, we found that MYCN also repressed the presumptive Wilms' tumour suppressor gene , with MYCN knockdown resulting in increased REST protein and concomitant repression of RE1-Silencing Transcription factor (REST) target genes. Together, our study identifies regulatory axes that interact with MYCN, providing novel pathways for potential targeted therapeutics for poor-prognosis Wilms' tumour.
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http://dx.doi.org/10.3390/cancers13040656DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7915280PMC
February 2021

A Combined Proteomics and Mendelian Randomization Approach to Investigate the Effects of Aspirin-Targeted Proteins on Colorectal Cancer.

Cancer Epidemiol Biomarkers Prev 2021 03 14;30(3):564-575. Epub 2020 Dec 14.

Nutrition and Metabolism Section, International Agency for Research on Cancer, World Health Organization, Lyon, France.

Background: Evidence for aspirin's chemopreventative properties on colorectal cancer (CRC) is substantial, but its mechanism of action is not well-understood. We combined a proteomic approach with Mendelian randomization (MR) to identify possible new aspirin targets that decrease CRC risk.

Methods: Human colorectal adenoma cells (RG/C2) were treated with aspirin (24 hours) and a stable isotope labeling with amino acids in cell culture (SILAC) based proteomics approach identified altered protein expression. Protein quantitative trait loci (pQTLs) from INTERVAL ( = 3,301) and expression QTLs (eQTLs) from the eQTLGen Consortium ( = 31,684) were used as genetic proxies for protein and mRNA expression levels. Two-sample MR of mRNA/protein expression on CRC risk was performed using eQTL/pQTL data combined with CRC genetic summary data from the Colon Cancer Family Registry (CCFR), Colorectal Transdisciplinary (CORECT), Genetics and Epidemiology of Colorectal Cancer (GECCO) consortia and UK Biobank (55,168 cases and 65,160 controls).

Results: Altered expression was detected for 125/5886 proteins. Of these, aspirin decreased MCM6, RRM2, and ARFIP2 expression, and MR analysis showed that a standard deviation increase in mRNA/protein expression was associated with increased CRC risk (OR: 1.08, 95% CI, 1.03-1.13; OR: 3.33, 95% CI, 2.46-4.50; and OR: 1.15, 95% CI, 1.02-1.29, respectively).

Conclusions: MCM6 and RRM2 are involved in DNA repair whereby reduced expression may lead to increased DNA aberrations and ultimately cancer cell death, whereas ARFIP2 is involved in actin cytoskeletal regulation, indicating a possible role in aspirin's reduction of metastasis.

Impact: Our approach has shown how laboratory experiments and population-based approaches can combine to identify aspirin-targeted proteins possibly affecting CRC risk.
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http://dx.doi.org/10.1158/1055-9965.EPI-20-1176DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8086774PMC
March 2021

BCL‑3 promotes cyclooxygenase‑2/prostaglandin E2 signalling in colorectal cancer.

Int J Oncol 2020 05 16;56(5):1304-1313. Epub 2020 Mar 16.

Colorectal Tumour Biology Group, School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, United Kingdom.

First discovered as an oncogene in leukaemia, recent reports highlight an emerging role for the proto‑oncogene BCL‑3 in solid tumours. Importantly, BCL‑3 expression is upregulated in >30% of colorectal cancer cases and is reported to be associated with a poor prognosis. However, the mechanism by which BCL‑3 regulates tumorigenesis in the large intestine is yet to be fully elucidated. In the present study, it was shown for the first time that knocking down BCL‑3 expression suppressed cyclooxygenase‑2 (COX‑2)/prostaglandin E2 (PGE2) signalling in colorectal cancer cells, a pathway known to drive several of the hallmarks of cancer. RNAi‑mediated suppression of BCL‑3 expression decreased COX‑2 expression in colorectal cancer cells both at the mRNA and protein level. This reduction in COX‑2 expression resulted in a significant and functional reduction (30‑50%) in the quantity of pro‑tumorigenic PGE2 produced by the cancer cells, as shown by enzyme linked immunoassays and medium exchange experiments. In addition, inhibition of BCL‑3 expression also significantly suppressed cytokine‑induced (TNF‑α or IL‑1β) COX‑2 expression. Taken together, the results of the present study identified a novel role for BCL‑3 in colorectal cancer and suggested that expression of BCL‑3 may be a key determinant in the COX‑2‑meditated response to inflammatory cytokines in colorectal tumour cells. These results suggest that targeting BCL‑3 to suppress PGE2 synthesis may represent an alternative or complementary approach to using non‑steroidal anti‑inflammatory drugs [(NSAIDs), which inhibit cyclooxygenase activity and suppress the conversion of arachidonic acid to prostaglandin], for prevention and/or recurrence in PGE2‑driven tumorigenesis.
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http://dx.doi.org/10.3892/ijo.2020.5013DOI Listing
May 2020

A Wnt-BMP4 Signaling Axis Induces MSX and NOTCH Proteins and Promotes Growth Suppression and Differentiation in Neuroblastoma.

Cells 2020 03 23;9(3). Epub 2020 Mar 23.

Cancer Epigenetics Laboratory, School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK.

The Wnt and bone morphogenetic protein (BMP) signaling pathways are known to be crucial in the development of neural crest lineages, including the sympathetic nervous system. Surprisingly, their role in paediatric neuroblastoma, the prototypic tumor arising from this lineage, remains relatively uncharacterised. We previously demonstrated that Wnt/b-catenin signaling can have cell-type-specific effects on neuroblastoma phenotypes, including growth inhibition and differentiation, and that BMP4 mRNA and protein were induced by Wnt3a/Rspo2. In this study, we characterised the phenotypic effects of BMP4 on neuroblastoma cells, demonstrating convergent induction of MSX homeobox transcription factors by Wnt and BMP4 signaling and BMP4-induced growth suppression and differentiation. An immunohistochemical analysis of BMP4 expression in primary neuroblastomas confirms a striking absence of BMP4 in poorly differentiated tumors, in contrast to a high expression in ganglion cells. These results are consistent with a tumor suppressive role for BMP4 in neuroblastoma. RNA sequencing following BMP4 treatment revealed induction of Notch signaling, verified by increases of Notch3 and Hes1 proteins. Together, our data demonstrate, for the first time, Wnt-BMP-Notch signaling crosstalk associated with growth suppression of neuroblastoma.
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http://dx.doi.org/10.3390/cells9030783DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7140810PMC
March 2020

Wnt Signaling Is a Major Determinant of Neuroblastoma Cell Lineages.

Front Mol Neurosci 2019 16;12:90. Epub 2019 Apr 16.

Cancer Epigenetics Laboratory, School of Cellular and Molecular Medicine, University of Bristol, Bristol, United Kingdom.

The neural crest (NC), which has been referred to as the fourth germ layer, comprises a multipotent cell population which will specify diverse cells and tissues, including craniofacial cartilage and bones, melanocytes, the adrenal medulla and the peripheral nervous system. These cell fates are known to be determined by gene regulatory networks (GRNs) acting at various stages of NC development, such as induction, specification, and migration. Although transcription factor hierarchies and some of their interplay with morphogenetic signaling pathways have been characterized, the full complexity of activities required for regulated development remains uncharted. Deregulation of these pathways may contribute to tumorigenesis, as in the case of neuroblastoma, a frequently lethal embryonic cancer thought to arise from the sympathoadrenal lineage of the NC. In this "Hypothesis and Theory" article, we utilize the next generation sequencing data from neuroblastoma cells and tumors to evaluate the possible influences of Wnt signaling on NC GRNs and on neuroblastoma cell lineages. We propose that Wnt signaling is a major determinant of regulatory networks that underlie mesenchymal/neural crest cell (NCC)-like cell identities through PRRX1 and YAP/TAZ transcription factors. Furthermore, Wnt may also co-operate with Hedgehog signaling in driving proneural differentiation programmes along the adrenergic (ADRN) lineage. Elucidation of Signaling Regulatory Networks can augment and complement GRNs in characterizing cell identities, which may in turn contribute to the design of improved therapeutics tailored to primary and relapsing neuroblastoma.
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http://dx.doi.org/10.3389/fnmol.2019.00090DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6476918PMC
April 2019

BCL-3 promotes a cancer stem cell phenotype by enhancing β-catenin signalling in colorectal tumour cells.

Dis Model Mech 2019 03 4;12(3). Epub 2019 Mar 4.

Colorectal Tumour Biology Group, School of Cellular and Molecular Medicine, Faculty of Life Sciences, Biomedical Sciences Building, University Walk, University of Bristol, Bristol BS8 1TD, UK

To decrease bowel cancer incidence and improve survival, we need to understand the mechanisms that drive tumorigenesis. Recently, B-cell lymphoma 3 (BCL-3; a key regulator of NF-κB signalling) has been recognised as an important oncogenic player in solid tumours. Although reported to be overexpressed in a subset of colorectal cancers (CRCs), the role of BCL-3 expression in colorectal tumorigenesis remains poorly understood. Despite evidence in the literature that BCL-3 may interact with β-catenin, it is perhaps surprising, given the importance of deregulated Wnt/β-catenin/T-cell factor (TCF) signalling in colorectal carcinogenesis, that the functional significance of this interaction is not known. Here, we show for the first time that BCL-3 acts as a co-activator of β-catenin/TCF-mediated transcriptional activity in CRC cell lines and that this interaction is important for Wnt-regulated intestinal stem cell gene expression. We demonstrate that targeting BCL-3 expression (using RNA interference) reduced β-catenin/TCF-dependent transcription and the expression of intestinal stem cell genes and In contrast, the expression of canonical Wnt targets Myc and cyclin D1 remained unchanged. Furthermore, we show that BCL-3 increases the functional stem cell phenotype, as shown by colorectal spheroid and tumoursphere formation in 3D culture conditions. We propose that BCL-3 acts as a driver of the stem cell phenotype in CRC cells, potentially promoting tumour cell plasticity and therapeutic resistance. As recent reports highlight the limitations of directly targeting cancer stem cells (CSCs), we believe that identifying and targeting drivers of stem cell plasticity have significant potential as new therapeutic targets.This article has an associated First Person interview with the first author of the paper.
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http://dx.doi.org/10.1242/dmm.037697DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6451435PMC
March 2019

LEF-1 drives aberrant β-catenin nuclear localization in myeloid leukemia cells.

Haematologica 2019 07 10;104(7):1365-1377. Epub 2019 Jan 10.

Department of Haematology, Division of Cancer and Genetics, School of Medicine, Cardiff University, UK

Canonical Wnt/β-catenin signaling is frequently dysregulated in myeloid leukemias and is implicated in leukemogenesis. Nuclear-localized β-catenin is indicative of active Wnt signaling and is frequently observed in acute myeloid leukemia (AML) patients; however, some patients exhibit little or no nuclear β-catenin even where cytosolic β-catenin is abundant. Control of the subcellular localization of β-catenin therefore represents an additional mechanism regulating Wnt signaling in hematopoietic cells. To investigate the factors mediating the nuclear-localization of β-catenin, we carried out the first nuclear/cytoplasmic proteomic analysis of the β-catenin interactome in myeloid leukemia cells and identified putative novel β-catenin interactors. Comparison of interacting factors between Wnt-responsive cells (high nuclear β-catenin) Wnt-unresponsive cells (low nuclear β-catenin) suggested the transcriptional partner, LEF-1, could direct the nuclear-localization of β-catenin. The relative levels of nuclear LEF-1 and β-catenin were tightly correlated in both cell lines and in primary AML blasts. Furthermore, LEF-1 knockdown perturbed β-catenin nuclear-localization and transcriptional activation in Wnt-responsive cells. Conversely, LEF-1 overexpression was able to promote both nuclear-localization and β-catenin-dependent transcriptional responses in previously Wnt-unresponsive cells. This is the first β-catenin interactome study in hematopoietic cells and reveals LEF-1 as a mediator of nuclear β- catenin level in human myeloid leukemia.
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http://dx.doi.org/10.3324/haematol.2018.202846DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6601079PMC
July 2019

Cancer cell adaptation to hypoxia involves a HIF-GPRC5A-YAP axis.

EMBO Mol Med 2018 11;10(11)

Cancer Research UK Colorectal Tumour Biology Group, School of Cellular & Molecular Medicine, Faculty of Life Sciences University of Bristol, Bristol, UK

Hypoxia is a hallmark of solid tumours and a key physiological feature distinguishing cancer from normal tissue. However, a major challenge remains in identifying tractable molecular targets that hypoxic cancer cells depend on for survival. Here, we used SILAC-based proteomics to identify the orphan G protein-coupled receptor GPRC5A as a novel hypoxia-induced protein that functions to protect cancer cells from apoptosis during oxygen deprivation. Using genetic approaches and , we reveal HIFs as direct activators of transcription. Furthermore, we find that GPRC5A is upregulated in the colonic epithelium of patients with mesenteric ischaemia, and in colorectal cancers high correlates with hypoxia gene signatures and poor clinical outcomes. Mechanistically, we show that GPRC5A enables hypoxic cell survival by activating the Hippo pathway effector YAP and its anti-apoptotic target gene Importantly, we show that the apoptosis induced by GPRC5A depletion in hypoxia can be rescued by constitutively active YAP. Our study identifies a novel HIF-GPRC5A-YAP axis as a critical mediator of the hypoxia-induced adaptive response and a potential target for cancer therapy.
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http://dx.doi.org/10.15252/emmm.201708699DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6220329PMC
November 2018

Live imaging of wound angiogenesis reveals macrophage orchestrated vessel sprouting and regression.

EMBO J 2018 07 4;37(13). Epub 2018 Jun 4.

School of Biochemistry, University of Bristol, Bristol, UK

Wound angiogenesis is an integral part of tissue repair and is impaired in many pathologies of healing. Here, we investigate the cellular interactions between innate immune cells and endothelial cells at wounds that drive neoangiogenic sprouting in real time and Our studies in mouse and zebrafish wounds indicate that macrophages are drawn to wound blood vessels soon after injury and are intimately associated throughout the repair process and that macrophage ablation results in impaired neoangiogenesis. Macrophages also positively influence wound angiogenesis by driving resolution of anti-angiogenic wound neutrophils. Experimental manipulation of the wound environment to specifically alter macrophage activation state dramatically influences subsequent blood vessel sprouting, with premature dampening of tumour necrosis factor-α expression leading to impaired neoangiogenesis. Complementary human tissue culture studies indicate that inflammatory macrophages associate with endothelial cells and are sufficient to drive vessel sprouting via vascular endothelial growth factor signalling. Subsequently, macrophages also play a role in blood vessel regression during the resolution phase of wound repair, and their absence, or shifted activation state, impairs appropriate vessel clearance.
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http://dx.doi.org/10.15252/embj.201797786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028026PMC
July 2018

Wnt Signalling Drives Context-Dependent Differentiation or Proliferation in Neuroblastoma.

Neoplasia 2018 04 3;20(4):335-350. Epub 2018 Mar 3.

Cancer Epigenetics Laboratory, School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK. Electronic address:

Neuroblastoma is one of the commonest and deadliest solid tumours of childhood, and is thought to result from disrupted differentiation of the developing sympathoadrenergic lineage of the neural crest. Neuroblastoma exhibits intra- and intertumoural heterogeneity, with high risk tumours characterised by poor differentiation, which can be attributable to MYCN-mediated repression of genes involved in neuronal differentiation. MYCN is known to co-operate with oncogenic signalling pathways such as Alk, Akt and MEK/ERK signalling, and, together with c-MYC has been shown to be activated by Wnt signalling in various tissues. However, our previous work demonstrated that Wnt3a/Rspo2 treatment of some neuroblastoma cell lines can, paradoxically, decrease c-MYC and MYCN proteins. This prompted us to define the neuroblastoma-specific Wnt3a/Rspo2-driven transcriptome using RNA sequencing, and characterise the accompanying changes in cell biology. Here we report the identification of ninety Wnt target genes, and show that Wnt signalling is upstream of numerous transcription factors and signalling pathways in neuroblastoma. Using live-cell imaging, we show that Wnt signalling can drive differentiation of SK-N-BE(2)-C and SH-SY5Y cell-lines, but, conversely, proliferation of SK-N-AS cells. We show that cell-lines that differentiate show induction of pro-differentiation BMP4 and EPAS1 proteins, which is not apparent in the SK-N-AS cells. In contrast, SK-N-AS cells show increased CCND1, phosphorylated RB and E2F1 in response to Wnt3a/Rspo2, consistent with their proliferative response, and these proteins are not increased in differentiating lines. By meta-analysis of the expression of our 90 genes in primary tumour gene expression databases, we demonstrate discrete expression patterns of our Wnt genes in patient cohorts with different prognosis. Furthermore our analysis reveals interconnectivity within subsets of our Wnt genes, with one subset comprised of novel putative drivers of neuronal differentiation repressed by MYCN. Assessment of β-catenin immunohistochemistry shows high levels of β-catenin in tumours with better differentiation, further supporting a role for canonical Wnt signalling in neuroblastoma differentiation.
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http://dx.doi.org/10.1016/j.neo.2018.01.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5909736PMC
April 2018

LGR5 regulates pro-survival MEK/ERK and proliferative Wnt/β-catenin signalling in neuroblastoma.

Oncotarget 2015 Nov;6(37):40053-67

Cancer Epigenetics Laboratory and School of Cellular & Molecular Medicine, University of Bristol, Bristol, UK.

LGR5 is a marker of normal and cancer stem cells in various tissues where it functions as a receptor for R-spondins and increases canonical Wnt signalling amplitude. Here we report that LGR5 is also highly expressed in a subset of high grade neuroblastomas. Neuroblastoma is a clinically heterogenous paediatric cancer comprising a high proportion of poor prognosis cases (~40%) which are frequently lethal. Unlike many cancers, Wnt pathway mutations are not apparent in neuroblastoma, although previous microarray analyses have implicated deregulated Wnt signalling in high-risk neuroblastoma. We demonstrate that LGR5 facilitates high Wnt signalling in neuroblastoma cell lines treated with Wnt3a and R-spondins, with SK-N-BE(2)-C, SK-N-NAS and SH-SY5Y cell-lines all displaying strong Wnt induction. These lines represent MYCN-amplified, NRAS and ALK mutant neuroblastoma subtypes respectively. Wnt3a/R-Spondin treatment also promoted nuclear translocation of β-catenin, increased proliferation and activation of Wnt target genes. Strikingly, short-interfering RNA mediated knockdown of LGR5 induces dramatic Wnt-independent apoptosis in all three cell-lines, accompanied by greatly diminished phosphorylation of mitogen/extracellular signal-regulated kinases (MEK1/2) and extracellular signal-regulated kinases (ERK1/2), and an increase of BimEL, an apoptosis facilitator downstream of ERK. Akt signalling is also decreased by a Rictor dependent, PDK1-independent mechanism. LGR5 expression is cell cycle regulated and LGR5 depletion triggers G1 cell-cycle arrest, increased p27 and decreased phosphorylated retinoblastoma protein. Our study therefore characterises new cancer-associated pathways regulated by LGR5, and suggest that targeting of LGR5 may be of therapeutic benefit for neuroblastomas with diverse etiologies, as well as other cancers expressing high LGR5.
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http://dx.doi.org/10.18632/oncotarget.5548DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4741879PMC
November 2015

Circulating prostaglandins as biomarkers for colorectal cancer?

EBioMedicine 2015 02 28;2(2):105-6. Epub 2015 Jan 28.

School of Cellular and Molecular Medicine, University of Bristol, Medical Sciences Building, Bristol BS8 1TD, UK.

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http://dx.doi.org/10.1016/j.ebiom.2015.01.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4484514PMC
February 2015

BCL-3 expression promotes colorectal tumorigenesis through activation of AKT signalling.

Gut 2016 07 1;65(7):1151-64. Epub 2015 Jun 1.

School of Cellular & Molecular Medicine, University of Bristol, Bristol, UK.

Objective: Colorectal cancer remains the fourth most common cause of cancer-related mortality worldwide. Here we investigate the role of nuclear factor-κB (NF-κB) co-factor B-cell CLL/lymphoma 3 (BCL-3) in promoting colorectal tumour cell survival.

Design: Immunohistochemistry was carried out on 47 tumour samples and normal tissue from resection margins. The role of BCL-3/NF-κB complexes on cell growth was studied in vivo and in vitro using an siRNA approach and exogenous BCL-3 expression in colorectal adenoma and carcinoma cells. The question whether BCL-3 activated the AKT/protein kinase B (PKB) pathway in colorectal tumour cells was addressed by western blotting and confocal microscopy, and the ability of 5-aminosalicylic acid (5-ASA) to suppress BCL-3 expression was also investigated.

Results: We report increased BCL-3 expression in human colorectal cancers and demonstrate that BCL-3 expression promotes tumour cell survival in vitro and tumour growth in mouse xenografts in vivo, dependent on interaction with NF-κB p50 or p52 homodimers. We show that BCL-3 promotes cell survival under conditions relevant to the tumour microenvironment, protecting both colorectal adenoma and carcinoma cells from apoptosis via activation of the AKT survival pathway: AKT activation is mediated via both PI3K and mammalian target of rapamycin (mTOR) pathways, leading to phosphorylation of downstream targets GSK-3β and FoxO1/3a. Treatment with 5-ASA suppressed BCL-3 expression in colorectal cancer cells.

Conclusions: Our study helps to unravel the mechanism by which BCL-3 is linked to poor prognosis in colorectal cancer; we suggest that targeting BCL-3 activity represents an exciting therapeutic opportunity potentially increasing the sensitivity of tumour cells to conventional therapy.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4941180PMC
http://dx.doi.org/10.1136/gutjnl-2014-308270DOI Listing
July 2016

Protein arginine methyltransferase 5 is a key regulator of the MYCN oncoprotein in neuroblastoma cells.

Mol Oncol 2015 Mar 15;9(3):617-27. Epub 2014 Nov 15.

Cancer Epigenetics Laboratory University of Bristol, Bristol BS8 1TD, UK. Electronic address:

Approximately half of poor prognosis neuroblastomas (NBs) are characterized by pathognomonic MYCN gene amplification and MYCN over-expression. Here we present data showing that short-interfering RNA mediated depletion of the protein arginine methyltransferase 5 (PRMT5) in cell-lines representative of NBs with MYCN gene amplification leads to greatly impaired growth and apoptosis. Growth suppression is not apparent in the MYCN-negative SH-SY5Y NB cell-line, or in two immortalized human fibroblast cell-lines. Immunoblotting of NB cell-lines shows that high PRMT5 expression is strongly associated with MYCN-amplification (P < 0.004, Mann-Whitney U-test) and immunohistochemical analysis of primary NBs reveals that whilst PRMT5 protein is ubiquitously expressed in the cytoplasm of most cells, MYCN-amplified tumours exhibit pronounced nuclear PRMT5 staining. PRMT5 knockdown in MYCN-overexpressing cells, including the SHEP-21N cell-line with inducible MYCN expression leads to a dramatic decrease in MYCN protein and MYCN-associated cell-death in SHEP-21N cells. Quantitative gene expression analysis and cycloheximide chase experiments suggest that PRMT5 regulates MYCN at a post-transcriptional level. Reciprocal co-immunoprecipitation experiments demonstrated that endogenous PRMT5 and MYCN interact in both SK-N-BE(2)C and NGP cell lines. By using liquid chromatography - tandem mass spectrometry (LC-MS/MS) analysis of immunoprecipitated MYCN protein, we identified several potential sites of arginine dimethylation on the MYCN protein. Together our studies implicate PRMT5 in a novel mode of MYCN post-translational regulation and suggest PRMT5 plays a major role in NB tumorigenesis. Small-molecule inhibitors of PRMT5 may therefore represent a novel therapeutic strategy for neuroblastoma and other cancers driven by the MYCN oncogene.
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http://dx.doi.org/10.1016/j.molonc.2014.10.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4359099PMC
March 2015

Autolysosomal β-catenin degradation regulates Wnt-autophagy-p62 crosstalk.

EMBO J 2013 Jul 4;32(13):1903-16. Epub 2013 Jun 4.

Cancer Research UK Colorectal Tumour Biology Group, School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK.

The Wnt/β-catenin signalling and autophagy pathways each play important roles during development, adult tissue homeostasis and tumorigenesis. Here we identify the Wnt/β-catenin signalling pathway as a negative regulator of both basal and stress-induced autophagy. Manipulation of β-catenin expression levels in vitro and in vivo revealed that β-catenin suppresses autophagosome formation and directly represses p62/SQSTM1 (encoding the autophagy adaptor p62) via TCF4. Furthermore, we show that during nutrient deprivation β-catenin is selectively degraded via the formation of a β-catenin-LC3 complex, attenuating β-catenin/TCF-driven transcription and proliferation to favour adaptation during metabolic stress. Formation of the β-catenin-LC3 complex is mediated by a W/YXXI/L motif and LC3-interacting region (LIR) in β-catenin, which is required for interaction with LC3 and non-proteasomal degradation of β-catenin. Thus, Wnt/β-catenin represses autophagy and p62 expression, while β-catenin is itself targeted for autophagic clearance in autolysosomes upon autophagy induction. These findings reveal a regulatory feedback mechanism that place β-catenin at a key cellular integration point coordinating proliferation with autophagy, with implications for targeting these pathways for cancer therapy.
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http://dx.doi.org/10.1038/emboj.2013.123DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3981178PMC
July 2013

LGR5 promotes survival in human colorectal adenoma cells and is upregulated by PGE2: implications for targeting adenoma stem cells with NSAIDs.

Carcinogenesis 2013 May 24;34(5):1150-7. Epub 2013 Jan 24.

Cancer Research UK Colorectal Tumour Biology Group, School of Cellular and Molecular Medicine, Medical Sciences Building, University Walk, University of Bristol, UK.

Cyclooxygenase-2 is overexpressed in the majority of colorectal tumours leading to elevated levels of prostaglandin E2 (PGE2), promoting many hallmarks of cancer. Importantly, PGE2 is reported to enhance Wnt/β-catenin signalling in colorectal carcinoma cells and in normal haematopoietic stem cells where it promotes stem cell function. Although Wnt signalling plays a crucial role in intestinal stem cells, the relationship between PGE2 and intestinal stem cells is unclear. Given that the key intestinal cancer stem cell marker LGR5 (leucine-rich G-protein coupled receptor 5) is a Wnt target and PGE2 enhances Wnt signalling, the focus of this study was to investigate whether PGE2 regulated LGR5 expression in colorectal adenoma cells and whether LGR5 was important for tumour cell survival. PGE2 upregulated LGR5 protein in adenoma (RG/C2) and carcinoma (DLD-1) cell lines. LGR5 knockdown induced cell death in RG/C2 and AA/C1 adenoma cells, suggesting that LGR5 has an important survival-promoting role in adenoma cells. Indeed, we detected LGR5 protein expression in 4 of 4 human adenoma cell lines. Furthermore, LGR5 small interfering RNA inhibited the survival-promoting effects of PGE2 in RG/C2, suggesting that PGE2 promotes adenoma cell survival, at least in part, by increasing LGR5 expression. These studies, therefore, show the first link between PGE2 and LGR5 in human colorectal adenoma and carcinoma cells and demonstrate a survival-promoting role of LGR5. As non-steroidal anti-inflammatory drugs (NSAIDs) cause adenomas to regress in FAP patients, these studies could have important implications for the mechanism by which NSAIDs are chemopreventive, as lowering PGE2 levels could reduce LGR5 expression and survival of LGR5(+) adenoma stem cells.
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http://dx.doi.org/10.1093/carcin/bgt020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3643418PMC
May 2013

β-catenin represses expression of the tumour suppressor 15-prostaglandin dehydrogenase in the normal intestinal epithelium and colorectal tumour cells.

Gut 2012 Sep 14;61(9):1306-14. Epub 2011 Nov 14.

Cancer Research UK Colorectal Tumour Biology Research Group, School of Cellular and Molecular Medicine, University Walk, University of Bristol, Bristol, UK.

Background: Cyclooxygenase-2 (COX-2) overexpression in colorectal cancer increases levels of its pro-tumorigenic product prostaglandin E2 (PGE(2)). The recently identified colorectal tumour suppressor 15-prostaglandin dehydrogenase (15-PGDH) catalyses prostaglandin turnover and is downregulated at a very early stage in colorectal tumorigenesis; however, the mechanism responsible remains unclear. As Wnt/β-catenin signalling is also deregulated early in colorectal neoplasia, a study was undertaken to determine whether β-catenin represses 15-PGDH expression.

Methods: The effect of modulating Wnt/β-catenin signalling (using β-catenin siRNA, mutant TCF4, Wnt3A or GSK3 inhibition) on 15-PGDH mRNA, protein expression and promoter activity was determined in colorectal cell lines by immunoblotting, qRT-PCR and reporter assays. The effect of β-catenin deletion in vivo was addressed by 15-PGDH immunostaining of β-catenin(-/lox)-villin-creERT2 mouse tissue. 15-PGDH promoter occupancy was determined using chromatin immunoprecipitation and PGE(2) levels by ELISA.

Results: The study shows for the first time that β-catenin knockdown upregulates 15-PGDH in colorectal adenoma and carcinoma cells without affecting COX-2 protein levels. A dominant negative mutant form of TCF4 (dnTCF4), unable to bind β-catenin, also upregulated 15-PGDH; conversely, increasing β-catenin activity using Wnt3A or GSK3 inhibition downregulated 15-PGDH. Importantly, inducible β-catenin deletion in vivo also upregulated intestinal epithelial 15-PGDH. 15-PGDH regulation occurred at the protein, mRNA and promoter activity levels and chromatin immunoprecipitation indicated β-catenin/TCF4 binding to the 15-PGDH promoter. β-catenin knockdown decreased PGE(2) levels, and this was significantly rescued by 15-PGDH siRNA.

Conclusion: These data suggest a novel role for β-catenin in promoting colorectal tumorigenesis through very early 15-PGDH suppression leading to increased PGE(2) levels, possibly even before COX-2 upregulation.
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http://dx.doi.org/10.1136/gutjnl-2011-300817DOI Listing
September 2012

Colon tumour cells increase PGE(2) by regulating COX-2 and 15-PGDH to promote survival during the microenvironmental stress of glucose deprivation.

Carcinogenesis 2011 Nov 16;32(11):1741-7. Epub 2011 Sep 16.

School of Cellular and Molecular Medicine, Cancer Research UK Colorectal Tumour Biology Research Group, University of Bristol, Bristol, BS8 1TD, UK.

Due to poor tumour-associated vasculature, tumour cells are subjected to a fluctuating microenvironment with periods of limited oxygen and glucose availability. Adaptive mechanisms to adverse microenvironments are important for tumour cell survival. The cyclooxygenase (COX)-2/prostaglandin E(2) (PGE(2)) pathway has key roles in colorectal tumorigenesis. Although glucose is important as an energy source and in maintaining endoplasmic reticulum homeostasis, relatively little is known regarding how tumour cells adapt to the microenvironmental stress of reduced glucose availability. Here, we report the novel findings that glucose deprivation of colorectal tumour cells not only increases COX-2 expression but also decreases 15-hydroxyprostaglandin dehydrogenase (15-PGDH) expression, resulting in increased extracellular PGE(2). Furthermore, we have shown that PGE(2) promotes tumour cell survival during glucose deprivation. Glucose deprivation enhances phosphoinositide 3-kinase/Akt activity, which has a role in both the up-regulation of COX-2 and down-regulation of 15-PGDH. Glucose deprivation also activates the unfolded protein response (UPR) resulting in elevated C/EBP-homologous protein (CHOP) expression. Interestingly, inhibiting CHOP expression by small interfering RNA during glucose deprivation attenuates the reduction in 15-PGDH expression. This is the first report linking activation of the UPR with a reduction in expression of tumour-suppressive 15-PGDH and may have implications for tumour cells' ability to survive exposure to therapeutic agents that activate the UPR. Our data suggest that diverse microenvironmental stresses converge to regulate PGE(2) as a common and crucial mediator of cell survival during adaptation to the tumour microenvironment and may lead to novel chemopreventive and therapeutic strategies.
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http://dx.doi.org/10.1093/carcin/bgr210DOI Listing
November 2011

The endogenous cannabinoid, anandamide, induces COX-2-dependent cell death in apoptosis-resistant colon cancer cells.

Int J Oncol 2010 Jul;37(1):187-93

Cancer Research UK Colorectal Tumour Biology Group, Department of Cellular and Molecular Medicine, School of Medical Sciences, University Walk, University of Bristol, BS8 1TD, UK.

Despite recent advances in understanding colorectal tumour biology, there is still a need to improve the 5-year survival rate of patients with colorectal cancer as approximately 40% of patients presenting with advanced disease will remain resistant to therapy. One of the major contributing factors in resistance to therapy is the failure of colorectal tumour cells to undergo apoptosis. Hence there is an urgent need to develop novel therapeutic approaches that can target apoptosis-resistant cells. To this end, we investigated the potential efficacy of the endogenous cannabinoid anandamide to induce cell death in apoptosis-resistant colon cancer cells. Here, for the first time, we show that anandamide can induce cell death in the apoptosis-resistant HCT116 Bax-/- colorectal cell line. Importantly, we provide direct genetic evidence that this induction of cell death is dependent on COX-2 expression. Interestingly, increased COX-2 expression also sensitised the SW480 colorectal cancer cell line (low endogenous COX-2) to anandamide-induced death, whereas COX-2 suppression by RNAi inhibited anandamide-induced cell death in the HCA7 colorectal cancer cell line (high endogenous COX-2 expression). This COX-2-dependent death was independent of cannabinoid receptor engagement (CB1 or CB2), and not a direct consequence of reactive oxygen species (ROS) formation. This study demonstrates a novel utilisation for COX-2 expression, targeting apoptotic defective colorectal cancer cells for destruction by anandamide. As COX-2 is not expressed in the normal colorectal epithelium, but highly expressed in colorectal tumours and apoptosis resistance contributes to treatment failure, these data suggest that anandamide has the potential to be an effective therapeutic in colorectal cancer.
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http://dx.doi.org/10.3892/ijo_00000666DOI Listing
July 2010

HGF/Met signalling promotes PGE(2) biogenesis via regulation of COX-2 and 15-PGDH expression in colorectal cancer cells.

Carcinogenesis 2009 Oct 28;30(10):1796-804. Epub 2009 Jul 28.

Cancer Research UK Colorectal Tumour Biology Group, Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, University Walk, Bristol, UK.

Evidence points towards a pivotal role for cyclooxygenase (COX)-2 in promoting colorectal tumorigenesis through increasing prostaglandin E(2) (PGE(2)) levels. PGE(2) signalling is closely associated with the survival, proliferation and invasion of colorectal cancer cells. Recently, a reduction in PGE(2) inactivation, a process mediated by the nicotinamide adenine dinucleotide (NAD+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH), has also been shown to promote tumoral PGE(2) accumulation. The hepatocyte growth factor (HGF) receptor, Met, is frequently over-expressed in colorectal tumours and promotes cancer growth, metastasis and resistance to therapy, although the mechanisms for this have not been fully elucidated. Here, we report that HGF/Met signalling can promote PGE(2) biogenesis in colorectal cancer cells via COX-2 up-regulation and 15-PGDH down-regulation at the protein and messenger RNA level. Pharmacological inhibition of MEK and PI3K suggested that both extracellular signal-regulated kinase (ERK) and AKT signalling are required for COX-2 protein up-regulation and 15-PGDH down-regulation downstream of Met. Notably, inhibition of Met with the small molecule inhibitor SU11274 reduced COX-2 expression and increased 15-PGDH expression in high Met-expressing cells. We also show that hypoxia potentiated HGF-driven COX-2 expression and enhanced PGE(2) release. Furthermore, inhibition of COX-2 impeded the growth-promoting effects of HGF, suggesting that the COX-2/PGE(2) pathway is an important mediator of HGF/Met signalling. These data reveal a critical role for HGF/Met signalling in promoting PGE(2) biogenesis in colorectal cancer cells. Targeting the crosstalk between these two important pathways may be useful for therapeutic treatment of colorectal cancer.
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http://dx.doi.org/10.1093/carcin/bgp183DOI Listing
October 2009

The COX-2/PGE2 pathway: key roles in the hallmarks of cancer and adaptation to the tumour microenvironment.

Carcinogenesis 2009 Mar 9;30(3):377-86. Epub 2009 Jan 9.

Department of Cellular and Molecular Medicine, Cancer Research UK Colorectal Tumour Biology Group, University of Bristol, University Walk, Clifton, Bristol, UK.

It is widely accepted that alterations to cyclooxygenase-2 (COX-2) expression and the abundance of its enzymatic product prostaglandin E(2) (PGE(2)) have key roles in influencing the development of colorectal cancer. Deregulation of the COX-2/PGE(2) pathway appears to affect colorectal tumorigenesis via a number of distinct mechanisms: promoting tumour maintenance and progression, encouraging metastatic spread, and perhaps even participating in tumour initiation. Here, we review the role of COX-2/PGE(2) signalling in colorectal tumorigenesis and highlight its ability to influence the hallmarks of cancer--attributes defined by Hanahan and Weinberg as being requisite for tumorigenesis. In addition, we consider components of the COX-prostaglandin pathway emerging as important regulators of tumorigenesis; namely, the prostanoid (EP) receptors, 15-hydroxyprostaglandin dehydrogenase and the prostaglandin transporter. Finally, based on recent findings, we propose a model for the cellular adaptation to the hypoxic tumour microenvironment that encompasses the interplay between COX-2, hypoxia-inducible factor 1 and dynamic switches in beta-catenin function that fine-tune signalling networks to meet the ever-changing demands of a tumour.
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http://dx.doi.org/10.1093/carcin/bgp014DOI Listing
March 2009

Hypomethylation and aberrant expression of the glioma pathogenesis-related 1 gene in Wilms tumors.

Neoplasia 2007 Nov;9(11):970-8

Department of Cellular and Molecular Medicine, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.

Wilms tumors (WTs) have a complex etiology, displaying genetic and epigenetic changes, including loss of imprinting (LOI) and tumor suppressor gene silencing. To identify new regions of epigenetic perturbation in WTs, we screened kidney and tumor DNA using CpG island (CGI) tags associated with cancer-specific DNA methylation changes. One such tag corresponded to a paralog of the glioma pathogenesis-related 1/related to testis-specific, vespid, and pathogenesis proteins 1 (GLIPR1/RTVP-1) gene, previously reported to be a tumor-suppressor gene silenced by hypermethylation in prostate cancer. Here we report methylation analysis of the GLIPR1/RTVP-1 gene in WTs and normal fetal and pediatric kidneys. Hypomethylation of the GLIPR1/RTVP-1 5'-region in WTs relative to normal tissue is observed in 21/24 (87.5%) of WTs analyzed. Quantitative analysis of GLIPR1/RTVP-1 expression in 24 WTs showed elevated transcript levels in 16/24 WTs (67%), with 12 WTs displaying in excess of 20-fold overexpression relative to fetal kidney (FK) control samples. Immunohistochemical analysis of FK and WT corroborates the RNA expression data and reveals high GLIPR1/RTVP-1 in WT blastemal cells together with variable levels in stromal and epithelial components. Hypomethylation is also evident in the WT precursor lesions and nephrogenic rests (NRs), supporting a role for GLIPR1/RTVP-1 deregulation early in Wilms tumorigenesis. Our data show that, in addition to gene dosage changes arising from LOI and hypermethylation-induced gene silencing, gene activation resulting from hypomethylation is also prevalent in WTs.
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http://dx.doi.org/10.1593/neo.07661DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2077888PMC
November 2007

The cannabinoid delta(9)-tetrahydrocannabinol inhibits RAS-MAPK and PI3K-AKT survival signalling and induces BAD-mediated apoptosis in colorectal cancer cells.

Int J Cancer 2007 Nov;121(10):2172-80

Department of Cellular and Molecular Medicine, Cancer Research UK, Colorectal Tumour Biology Group, School of Medical Sciences, University of Bristol, University Walk, Bristol, United Kingdom.

Deregulation of cell survival pathways and resistance to apoptosis are widely accepted to be fundamental aspects of tumorigenesis. As in many tumours, the aberrant growth and survival of colorectal tumour cells is dependent upon a small number of highly activated signalling pathways, the inhibition of which elicits potent growth inhibitory or apoptotic responses in tumour cells. Accordingly, there is considerable interest in therapeutics that can modulate survival signalling pathways and target cancer cells for death. There is emerging evidence that cannabinoids, especially Delta(9)-tetrahydrocannabinol (THC), may represent novel anticancer agents, due to their ability to regulate signalling pathways critical for cell growth and survival. Here, we report that CB1 and CB2 cannabinoid receptors are expressed in human colorectal adenoma and carcinoma cells, and show for the first time that THC induces apoptosis in colorectal cancer cells. THC-induced apoptosis was rescued by pharmacological blockade of the CB1, but not CB2, cannabinoid receptor. Importantly, THC treatment resulted in CB1-mediated inhibition of both RAS-MAPK/ERK and PI3K-AKT survival signalling cascades; two key cell survival pathways frequently deregulated in colorectal tumours. The inhibition of ERK and AKT activity by THC was accompanied by activation of the proapoptotic BCL-2 family member BAD. Reduction of BAD protein expression by RNA interference rescued colorectal cancer cells from THC-induced apoptosis. These data suggest an important role for CB1 receptors and BAD in the regulation of apoptosis in colorectal cancer cells. The use of THC, or selective targeting of the CB1 receptor, may represent a novel strategy for colorectal cancer therapy.
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http://dx.doi.org/10.1002/ijc.22917DOI Listing
November 2007
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