ORCID Profile
0000-0003-2735-5509
Current Organisations
Australian National University
,
Universitätsklinikum Freiburg
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Informa UK Limited
Date: 12-2002
Publisher: Springer Science and Business Media LLC
Date: 13-11-2017
DOI: 10.1038/S41467-017-01514-3
Abstract: Renal angiomyolipomas (AML) contain an admixture of clonal tumour cells with features of several different mesenchymal lineages, implying the existence of an unidentified AML neoplastic stem cell. Biallelic inactivation of TSC2 or TSC1 is believed to represent the driving event in these tumours. Here we show that TSC2 knockdown transforms senescence-resistant cultured mouse and human renal epithelial cells into neoplastic stem cells that serially propagate renal AML-like tumours in mice. mTOR inhibitory therapy of mouse AML allografts mimics the clinical responses of human renal AMLs. Deletion of Tsc1 in mouse renal epithelia causes differentiation in vivo into cells expressing characteristic AML markers. Human renal AML and a renal AML cell line express proximal tubule markers. We describe the first mouse models of renal AML and provide evidence that these mesenchymal tumours originate from renal proximal tubule epithelial cells, uncovering an unexpected pathological differentiation plasticity of the proximal tubule.
Publisher: Elsevier BV
Date: 04-2020
Publisher: American Association for Cancer Research (AACR)
Date: 31-03-2016
DOI: 10.1158/0008-5472.CAN-15-1859
Abstract: The von Hippel–Lindau (VHL) tumor suppressor gene is inactivated in the majority of clear cell renal cell carcinomas (ccRCC), but genetic ablation of Vhl alone in mouse models is insufficient to recapitulate human tumorigenesis. One function of pVHL is to regulate the stability of the hypoxia-inducible factors (HIF), which become constitutively activated in the absence of pVHL. In established ccRCC, HIF1α has been implicated as a renal tumor suppressor, whereas HIF2α is considered an oncoprotein. In this study, we investigated the contributions of HIF1α and HIF2α to ccRCC initiation in the context of Vhl deficiency. We found that deleting Vhl plus Hif1a or Hif2a specifically in the renal epithelium did not induce tumor formation. However, HIF1α and HIF2α differentially regulated cell proliferation, mitochondrial abundance and oxidative capacity, glycogen accumulation, and acquisition of a clear cell phenotype in Vhl-deficient renal epithelial cells. HIF1α, but not HIF2α, induced Warburg-like metabolism characterized by increased glycolysis, decreased oxygen consumption, and decreased ATP production in mouse embryonic fibroblasts, providing insights into the cellular changes potentially occurring in Vhl mutant renal cells before ccRCC formation. Importantly, deletion of either Hif1a or Hif2a completely prevented the formation of renal cysts and tumors in Vhl/Trp53 mutant mice. These findings argue that both HIF1α and HIF2α exert protumorigenic functions during the earliest stages of cyst and tumor formation in the kidney. Cancer Res 76(7) 2025–36. ©2016 AACR.
Publisher: Elsevier BV
Date: 07-2013
DOI: 10.1016/J.EJCA.2013.02.024
Abstract: The von Hippel-Lindau tumour suppressor protein (pVHL) controls distinct cellular responses ranging from targeting hypoxia inducible factor α (HIFα) subunits for degradation and promotion of chromosomal stability to the regulation of microtubule dynamics. pVHL is produced in mammalian cells as a long and a short isoform, derived from alternate translational initiation sites in a single Vhl mRNA. However, it is unclear whether these isoforms have different cell biological activities that may represent different tumour suppressor activities of pVHL. Through a knock-in strategy to mutate the first translational initiation site from methionine to leucine (M1L) we have genetically deleted the pVHL long protein isoform in mice, allowing dissection of isoform-specific functions of pVHL. Vhl(M1L/M1L) mice exhibit no obvious phenotypic abnormalities. While numerous pVHL-mediated activities, including degradation of HIFα transcription factors, are unaffected, microtubule dynamics are altered in primary cells derived from Vhl(M1L/M1L) mice to an extent similar to that seen following complete loss of pVHL function. We conclude that the microtubule-regulating function and the HIFα-regulating function of pVHL are separable activities mediated by different protein isoforms.
Publisher: EMBO
Date: 22-04-2013
Publisher: MDPI AG
Date: 08-03-2023
Abstract: Clear cell renal cell carcinoma (ccRCC) is the most common histological subtype of renal cancer, and inactivation of the VHL tumor suppressor gene is found in almost all cases of hereditary and sporadic ccRCCs. CcRCC is associated with the reprogramming of fatty acid metabolism, and stearoyl-CoA desaturases (SCDs) are the main enzymes controlling fatty acid composition in cells. In this study, we report that mRNA and protein expression of the stearoyl-CoA desaturase SCD5 is downregulated in VHL-deficient cell lines. Similarly, in C. elegans vhl-1 mutants, FAT-7/SCD5 activity is repressed, supporting an evolutionary conservation. SCD5 regulation by VHL depends on HIF, and loss of SCD5 promotes cell proliferation and a metabolic shift towards ceramide production. In summary, we identify a novel regulatory function of VHL in relation to SCD5 and fatty acid metabolism, and propose a new mechanism of how loss of VHL may contribute to ccRCC tumor formation and progression.
Publisher: Public Library of Science (PLoS)
Date: 05-10-2017
Publisher: Wiley
Date: 30-05-2016
DOI: 10.1002/PATH.4736
Abstract: The von Hippel-Lindau (VHL) tumour suppressor gene is bi-allelically inactivated in the majority of cases of clear cell renal cell carcinoma (ccRCC) however, Vhl knockout mouse models do not recapitulate human ccRCC, implying that additional mutations are required for tumour formation. Mutational inactivation of VHL sensitises renal epithelial cells to lose the primary cilium in response to other mutations or extracellular stimuli. Loss of cilia is believed to represent a second hit in VHL mutant cells that causes the development of cystic lesions that, in some cases, can progress to ccRCC. Supporting this idea, genetic ablation of the primary cilium by deletion of the kinesin family member 3A (Kif3a) gene cooperates with loss of Vhl to accelerate cyst formation in mouse kidneys. Additionally, aged Vhl/Trp53 double-mutant mice develop renal cysts and tumours at a relatively low incidence, suggesting that there is a genetic cooperation between VHL and TP53 mutation in the development of ccRCC. Here we generated renal epithelium-specific Kif3a/Trp53 and Vhl/Kif3a/Trp53 mutant mice to investigate whether primary cilium deletion would accelerate the development of cystic precursor lesions or cause their progression to ccRCC. Longitudinal microcomputed tomography (μCT) imaging and histopathological analyses revealed an increased rate of cyst formation, increased proportion of cysts with proliferating cells, higher frequency of atypical cysts as well as the development of neoplasms in Vhl/Kif3a/Trp53 mutant kidneys compared to Kif3a/Trp53 or Vhl/Kif3a mutant kidneys. These findings demonstrate that primary cilium loss, in addition to Vhl and Trp53 losses, promotes the transition towards malignancy and provide further evidence that the primary cilium functions as a tumour suppressor organelle in the kidney. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Publisher: Elsevier BV
Date: 12-1999
Publisher: Springer Science and Business Media LLC
Date: 18-06-2015
DOI: 10.1038/NCOMMS8227
Abstract: Enhancement of cellular senescence in tumours triggers a stable cell growth arrest and activation of an antitumour immune response that can be exploited for cancer therapy. Currently, there are only a limited number of targeted therapies that act by increasing senescence in cancers, but the majority of them are not selective and also target healthy cells. Here we developed a chemogenomic screening to identify compounds that enhance senescence in PTEN-deficient cells without affecting normal cells. By using this approach, we identified casein kinase 2 (CK2) as a pro-senescent target. Mechanistically, we show that Pten loss increases CK2 levels by activating STAT3. CK2 upregulation in Pten null tumours affects the stability of Pml, an essential regulator of senescence. However, CK2 inhibition stabilizes Pml levels enhancing senescence in Pten null tumours. Taken together, our screening strategy has identified a novel STAT3-CK2-PML network that can be targeted for pro-senescence therapy for cancer.
Publisher: Impact Journals, LLC
Date: 12-08-2016
Publisher: MDPI AG
Date: 25-09-2021
Abstract: Specific inhibitors of HIF-2α have recently been approved for the treatment of ccRCC in VHL disease patients and have shown encouraging results in clinical trials for metastatic sporadic ccRCC. However, not all patients respond to therapy and pre-clinical and clinical studies indicate that intrinsic as well as acquired resistance mechanisms to HIF-2α inhibitors are likely to represent upcoming clinical challenges. It would be desirable to have additional therapeutic options for the treatment of HIF-2α inhibitor resistant ccRCCs. Here we investigated the effects on tumor growth and on the tumor microenvironment of three different direct and indirect HIF-α inhibitors, namely the HIF-2α-specific inhibitor PT2399, the dual HIF-1α/HIF-2α inhibitor Acriflavine, and the S1P signaling pathway inhibitor FTY720, in the autochthonous Vhl/Trp53/Rb1 mutant ccRCC mouse model and validated these findings in human ccRCC cell culture models. We show that FTY720 and Acriflavine exhibit therapeutic activity in several different settings of HIF-2α inhibitor resistance. We also identify that HIF-2α inhibition strongly suppresses T cell activation in ccRCC. These findings suggest prioritization of sphingosine pathway inhibitors for clinical testing in ccRCC patients and also suggest that HIF-2α inhibitors may inhibit anti-tumor immunity and might therefore be contraindicated for combination therapies with immune checkpoint inhibitors.
Publisher: Elsevier BV
Date: 07-2018
DOI: 10.1016/J.SCITOTENV.2018.01.012
Abstract: Through litter decomposition enormous amounts of carbon is emitted to the atmosphere. Numerous large-scale decomposition experiments have been conducted focusing on this fundamental soil process in order to understand the controls on the terrestrial carbon transfer to the atmosphere. However, previous studies were mostly based on site-specific litter and methodologies, adding major uncertainty to syntheses, comparisons and meta-analyses across different experiments and sites. In the TeaComposition initiative, the potential litter decomposition is investigated by using standardized substrates (Rooibos and Green tea) for comparison of litter mass loss at 336 sites (ranging from -9 to +26 °C MAT and from 60 to 3113 mm MAP) across different ecosystems. In this study we tested the effect of climate (temperature and moisture), litter type and land-use on early stage decomposition (3 months) across nine biomes. We show that litter quality was the predominant controlling factor in early stage litter decomposition, which explained about 65% of the variability in litter decomposition at a global scale. The effect of climate, on the other hand, was not litter specific and explained <0.5% of the variation for Green tea and 5% for Rooibos tea, and was of significance only under unfavorable decomposition conditions (i.e. xeric versus mesic environments). When the data were aggregated at the biome scale, climate played a significant role on decomposition of both litter types (explaining 64% of the variation for Green tea and 72% for Rooibos tea). No significant effect of land-use on early stage litter decomposition was noted within the temperate biome. Our results indicate that multiple drivers are affecting early stage litter mass loss with litter quality being dominant. In order to be able to quantify the relative importance of the different drivers over time, long-term studies combined with experimental trials are needed.
Publisher: Informa UK Limited
Date: 07-2008
DOI: 10.1128/MCB.02132-07
Publisher: Wiley
Date: 11-04-2019
DOI: 10.1002/PATH.5267
Publisher: Wiley
Date: 07-2014
DOI: 10.1002/PATH.4390
Abstract: Endometrial cancer is the most frequently occurring malignancy of the female genital tract in Western countries. Although in many cases surgically curable, about 30% of the tumours represent an aggressive and untreatable disease. In an attempt to establish a reliable prognostic marker for endometrial carcinomas disregarding their histological ersity, we investigated the expression of KPNA2, a mediator of nucleocytoplasmic transport, and other cell proliferation-associated proteins and their correlation with cancer progression. We analysed patient tissue microarrays (TMAs) assembled from 527 endometrial cancer tissue specimens and uterus s les from a Trp53 knockout mouse model of endometrial cancer. Our data show that KPNA2 expression was significantly up-regulated in human endometrial carcinomas and associated with higher tumour grade (p = 0.026), higher FIGO stage (p = 0.027), p53 overexpression (p < 0.001), activation of the PI3K/AKT pathway, and epithelial-mesenchymal transition. Increased nuclear KPNA2 immunoreactivity was identified as a novel predictor of overall survival, independent of well-established prognostic factors in Cox regression analyses (hazard ratio 1.7, 95% CI 1.13-2.56, p = 0.01). No significant association between KPNA2 expression and endometrial cancer subtype was detected. In the mouse model, KPNA2 showed increased expression levels from precancerous (EmgD, EIC) to far-advanced invasive lesions. We further investigated the cell proliferation capacity after siRNA-mediated KPNA2 knockdown in the human endometrial cancer cell line MFE-296. KPNA2 silencing led to decreased proliferation of the cancer cells, suggesting interplay of the protein with the cell cycle. Taken together, increased expression of KPNA2 is an independent prognostic marker for poor survival. The mechanism of enhanced nucleocytoplasmic transport by KPNA2 overexpression seems a common event in aggressive cancers since we have shown a significant correlation of KPNA2 expression and tumour aggressiveness in a large variety of other solid tumour entities. Introducing KPNA2 immunohistochemistry in routine diagnostics may allow for the identification of patients who need more aggressive treatment regimens.
Publisher: Proceedings of the National Academy of Sciences
Date: 07-03-2003
Abstract: The Drosophila SINA (seven in absentia) protein and its mammalian orthologs (Siah, seven in absentia homolog) are RING domain proteins that function in E3 ubiquitin ligase complexes and facilitate ubiquitination and degradation of a wide range of cellular proteins, including β-catenin. Despite these erse targets, the means by which SINA/Siah recognize substrates or binding proteins has remained unknown. Here we identify a peptide motif (RPVAxVxPxxR) that mediates the interaction of Siah protein with a range of protein partners. Sequence alignment and mutagenesis scanning revealed residues that are important to this interaction. This consensus sequence correctly predicted a high-affinity interaction with a peptide from the cytoskeletal protein plectin-1 (residues 95–117). The unusually high-affinity binding obtained with a 23-residue peptide ( K Dapp = 29 nM with SINA) suggests that it may serve as a useful dominant negative reagent for SINA/Siah proteins.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2021
Abstract: The hypoxia-inducible factor (HIF) pathway is a key mediator of cellular adaptation to low oxygen tension. The aldosterone-sensitive distal nephron is the site of active and highly ATP-consuming sodium reabsorption, according to the requirement of sodium balance. The authors found that activation of the HIF pathway in cultured principal cells led to decreased amiloride-sensitive current (reflecting decreased epithelial sodium channel [ENaC] activity) and decreased expression of ENaC subunits, whereas HIF silencing led to increased amiloride-sensitive current and expression of ENaC subunits. Hypoxic control mice displayed decreased γ ENaC, whereas HIF1 α knockout mice displayed increased γ ENaC. These findings suggest that the HIF pathway controls ENaC expression and activity, and may represent a negative feedback mechanism to prevent hypoxia and/or reactive oxygen species–induced cell damage under sustained stimulation of sodium transport. Active sodium reabsorption is the major factor influencing renal oxygen consumption and production of reactive oxygen species (ROS). Increased sodium reabsorption uses more oxygen, which may worsen medullary hypoxia and produce more ROS via enhanced mitochondrial ATP synthesis. Both mechanisms may activate the hypoxia-inducible factor (HIF) pathway. Because the collecting duct is exposed to low oxygen pressure and variations of active sodium transport, we assessed whether the HIF pathway controls epithelial sodium channel (ENaC)–dependent sodium transport. We investigated HIF’s effect on ENaC expression in mpkCCD cl4 cells (a model of collecting duct principal cells) using real-time PCR and western blot and ENaC activity by measuring amiloride-sensitive current. We also assessed the effect of hypoxia and sodium intake on abundance of kidney sodium transporters in wild-type and inducible kidney tubule–specific Hif1α knockout mice. In cultured cells, activation of the HIF pathway by dimethyloxalylglycine or hypoxia inhibited sodium transport and decreased expression of β ENaC and γ ENaC, as well as of Na,K-ATPase. HIF1 α silencing increased β ENaC and γ ENaC expression and stimulated sodium transport. A constitutively active mutant of HIF1 α produced the opposite effect. Aldosterone and inhibition of the mitochondrial respiratory chain slowly activated the HIF pathway, suggesting that ROS may also activate HIF. Decreased γ ENaC abundance induced by hypoxia in normal mice was abolished in Hif1α knockout mice. Similarly, Hif1α knockout led to increased γ ENaC abundance under high sodium intake. This study reveals that γ ENaC expression and activity are physiologically controlled by the HIF pathway, which may represent a negative feedback mechanism to preserve oxygenation and/or prevent excessive ROS generation under increased sodium transport.
Publisher: Elsevier BV
Date: 12-2007
DOI: 10.1016/J.CEB.2007.10.001
Abstract: Functional inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene product, pVHL, leads to cancer in humans. It is widely accepted that pVHL functions to destabilise hypoxia inducible factor alpha (HIFalpha) subunits, key effectors of the hypoxia signalling pathway. However, growing evidence indicates that tumour suppression by pVHL also involves the control of a wide variety of HIFalpha-independent processes including microtubule dynamics, primary cilium maintenance, cell proliferation, neuronal apoptosis, extracellular matrix deposition and responses to DNA damage. Moreover, it is becoming apparent that tumour initiation requires not only VHL mutation but also the alteration of additional cooperating cancer pathways. These studies are beginning to provide insights into the signalling networks involving pVHL that normally control erse cellular processes and how disruption of these networks leads to tumour formation.
Publisher: Impact Journals, LLC
Date: 13-04-2018
Publisher: American Association for Cancer Research (AACR)
Date: 12-03-2015
DOI: 10.1158/1078-0432.CCR-14-2110
Abstract: Purpose: Basal cell carcinomas (BCCs) are tumors ignored by immune surveillance. Activated Hedgehog (Hh) signaling within primary cilia is a key driver in the pathogenesis of BCCs. We examined immune alterations during treatment with systemic Hh inhibitors. Experimental Design: We investigated biopsies from patients with BCC before (23 patients) and after 4 weeks of treatment (5 patients) with Hh signaling inhibitor. Ber-Ep4, BCL-2, Ki-67, CD4, CD8, MHC class I, HLA-DR-class II, and SOX9 were analyzed by immunohistochemistry. Primary cilia were analyzed by double immunofluorescence of acetylated tubulin and SOX9. Differential gene expression for 84 cytokines and chemokines was analyzed in 3 patients. Results: After 4 weeks of treatment, we found reduction of Ki-67, SOX9, Ber-EP4, and BCL-2 expression in tumors associated with morphologic signs of squamous differentiation. In addition, the number of cilia-positive BCC cells was significantly decreased. An upregulation of MHC I expression on the cell membranes of residual tumor cells and an influx of CD4+, HLA-DR-class II+, and CD8+ cells with invasion into the tumor cell nests were found. Finally, qPCR arrays showed the differential expression of genes involved in modulating immune responses. Conclusions: We show that Hh pathway inhibitor–induced tumor regression is accompanied by a dynamic change of the microenvironment with a disruption of immune privilege involving an influx of cytotoxic T cells, activation of the adaptive immune functions, and a profound alteration of the local chemokine/cytokine network. Clin Cancer Res 21(6) 1289–97. ©2015 AACR.
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.YEXMP.2017.02.009
Abstract: Detection of circulating tumor DNA (ctDNA) in blood of cancer patients is regarded as an important step towards personalized medicine and treatment monitoring. In the present study, we investigated the clinical applicability of ctDNA as liquid biopsy in renal cancer. ctDNA in serum and plasma s les derived from ccRCC and colon cancer patients as well as ctDNA isolated from RCC xenografts with known VHL mutation status was investigated using next generation sequencing (NGS). Additionally, a Taqman mutation specific assay was used for specific VHL mutation detection in blood. In our study, we successfully identified KRAS mutation in colon cancer patients. We also confirmed the presence of specific VHL mutations in ctDNA derived from RCC xenografts indicating the capability of renal tumors to release DNA into the blood circulation. However, we could not detect any VHL mutation in plasma or serum s les derived from nine ccRCC patients. To increase the sensitivity, a VHL mutation specific Taqman assay was tested. With this approach, the pVHL mutation p.Val130Leu in exon 2 in one patient was successfully detected. These data suggest a reduced tumor DNA shedding and an increased clearance of the tumor DNA from the circulation in renal cancer patients independently of tumor size, metastases, and necrosis. This implies that highly sensitive detection methods for mutation calling and prior knowledge of the mutation are required for liquid biopsies in ccRCC.
Publisher: Springer Science and Business Media LLC
Date: 09-10-2020
Publisher: American Society of Hematology
Date: 17-09-2020
Abstract: Acute graft-versus-host disease (GVHD) is a life-threatening complication after allogeneic hematopoietic cell transplantation (allo-HCT). Although currently used GVHD treatment regimens target the donor immune system, we explored here an approach that aims at protecting and regenerating Paneth cells (PCs) and intestinal stem cells (ISCs). Glucagon-like-peptide-2 (GLP-2) is an enteroendocrine tissue hormone produced by intestinal L cells. We observed that acute GVHD reduced intestinal GLP-2 levels in mice and patients developing GVHD. Treatment with the GLP-2 agonist, teduglutide, reduced de novo acute GVHD and steroid-refractory GVHD, without compromising graft-versus-leukemia (GVL) effects in multiple mouse models. Mechanistically GLP-2 substitution promoted regeneration of PCs and ISCs, which enhanced production of antimicrobial peptides and caused microbiome changes. GLP-2 expanded intestinal organoids and reduced expression of apoptosis-related genes. Low numbers of L cells in intestinal biopsies and high serum levels of GLP-2 were associated with a higher incidence of nonrelapse mortality in patients undergoing allo-HCT. Our findings indicate that L cells are a target of GVHD and that GLP-2–based treatment of acute GVHD restores intestinal homeostasis via an increase of ISCs and PCs without impairing GVL effects. Teduglutide could become a novel combination partner for immunosuppressive GVHD therapy to be tested in clinical trials.
Publisher: EMBO
Date: 08-06-2012
Publisher: Springer Science and Business Media LLC
Date: 29-05-2017
DOI: 10.1038/NM.4343
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2015
Publisher: Springer Science and Business Media LLC
Date: 22-04-2007
DOI: 10.1038/NCB1579
Abstract: Defects in the structure or function of the primary cilium, an antennae-like structure whose functional integrity has been linked to the suppression of uncontrolled kidney epithelial cell proliferation, are a common feature of genetic disorders characterized by kidney cysts. However, the mechanisms by which primary cilia are maintained remain poorly defined. von Hippel-Lindau (VHL) disease is characterized by the development of premalignant renal cysts and arises because of functional inactivation of the VHL tumour suppressor gene product, pVHL. Here, we show that pVHL and glycogen synthase kinase (GSK)3beta are key components of an interlinked signalling pathway that maintains the primary cilium. Although inactivation of either pVHL or GSK3beta alone did not affect cilia maintenance, their combined inactivation leads to loss of cilia. In VHL patients, GSK3beta is subjected to inhibitory phosphorylation in renal cysts, but not in early VHL mutant lesions, and these cysts exhibit reduced frequencies of primary cilia. We propose that pVHL and GSK3beta function together in a ciliary-maintenance signalling network, disruption of which enhances the vulnerability of cells to lose their cilia, thereby promoting cyst formation.
Publisher: Springer Science and Business Media LLC
Date: 17-08-2020
DOI: 10.1038/S41467-020-17873-3
Abstract: Mutational inactivation of VHL is the earliest genetic event in the majority of clear cell renal cell carcinomas (ccRCC), leading to accumulation of the HIF-1α and HIF-2α transcription factors. While correlative studies of human ccRCC and functional studies using human ccRCC cell lines have implicated HIF-1α as an inhibitor and HIF-2α as a promoter of aggressive tumour behaviours, their roles in tumour onset have not been functionally addressed. Herein we show using an autochthonous ccRCC model that Hif1a is essential for tumour formation whereas Hif2a deletion has only minor effects on tumour initiation and growth. Both HIF-1α and HIF-2α are required for the clear cell phenotype. Transcriptomic and proteomic analyses reveal that HIF-1α regulates glycolysis while HIF-2α regulates genes associated with lipoprotein metabolism, ribosome biogenesis and E2F and MYC transcriptional activities. HIF-2α-deficient tumours are characterised by increased antigen presentation, interferon signalling and CD8 + T cell infiltration and activation. Single copy loss of HIF1A or high levels of HIF2A mRNA expression correlate with altered immune microenvironments in human ccRCC. These studies reveal an oncogenic role of HIF-1α in ccRCC initiation and suggest that alterations in the balance of HIF-1α and HIF-2α activities can affect different aspects of ccRCC biology and disease aggressiveness.
Publisher: Wiley
Date: 11-2002
DOI: 10.1093/EMBOJ/CDF576
Abstract: TRAF2 serves as a central regulator of the cellular response to stress and cytokines through the regulation of key stress-signaling cascades. Here we demonstrate that wild-type, but not RING mutant, Siah2 targets TRAF2 for ubiquitylation and degradation in vitro. Siah2 mediates equally efficient ubiquitylation of RING mutant TRAF2. In vivo, Siah2 primarily targets TRAF2 for degradation under stress conditions. Tumor necrosis factor-alpha (TNF-alpha) and actinomycin D treatment results in accelerated TRAF2 degradation in wild-type mouse embryo fibroblasts (MEFs), as compared with Siah2(-/-) cells. Similarly, TRAF2 half-life is prolonged in Siah2(-/-) compared with wild-type MEFs subjected to stress stimuli. Siah2 efficiently decreases TNF-alpha-dependent induction of JNK activity and transcriptional activation of NF-kappaB. Apoptosis induced by TNF-alpha and actinomycin D treatment is increased upon expression of Siah2, or attenuated upon expression of TRAF2 or RING mutant Siah2. Identifying Siah2 as a regulator of TRAF2 stability reveals its role in the regulation of TRAF2 signaling following exposure to stress.
Publisher: American Society for Clinical Investigation
Date: 22-12-2022
DOI: 10.1172/JCI.INSIGHT.156087
Abstract: Metastatic clear cell renal cell carcinomas (ccRCC) are resistant to DNA damaging chemotherapies, limiting therapeutic options for patients whose tumours are resistant to tyrosine kinase inhibitors and/or immune checkpoint therapies. Here we show that mouse and human ccRCC are frequently characterised by high levels of endogenous DNA damage and that cultured ccRCC cells exhibit intact cellular responses to chemotherapy-induced DNA damage. We identify that pharmacological inhibition of the DNA damage sensing kinase ATR with the orally administered, potent and selective drug M4344 (also called gartisertib) induces anti-proliferative effects in ccRCC cells due to replication stress and the accumulation of DNA damage in S phase. In some cells, DNA damage persists into subsequent G2/M and G1 phases, leading to the frequent accumulation of micronuclei. Daily single agent treatment with M4344 inhibited the growth of ccRCC xenograft tumours. M4344 synergises with chemotherapeutic drugs including cisplatin and carboplatin and the PARP inhibitor olaparib in mouse and human ccRCC cells. Weekly M4344 plus cisplatin treatment showed in vivo therapeutic synergy in ccRCC xenografts and was efficacious in an autochthonous mouse ccRCC model. These studies identify ATR inhibition as a potential novel therapeutic option for ccRCC.
Publisher: Wiley
Date: 22-05-2008
Publisher: The Company of Biologists
Date: 15-02-2016
DOI: 10.1242/BIO.016584
Abstract: The proliferation of intestinal stem cells (ISCs) and differentiation of enteroblasts to form mature enteroendocrine cells and enterocytes in the Drosophila intestinal epithelium must be tightly regulated to maintain homeostasis. We show that genetic modulation of CyclinD/Cdk4 activity or mTOR-dependent signalling cell-autonomously regulates enterocyte growth, which influences ISC proliferation and enteroblast differentiation. Increased enterocyte growth results in higher numbers of ISCs and defective enterocyte growth reduces ISC abundance and proliferation in the midgut. Adult midguts deficient for Cdk4 show severe disruption of intestinal homeostasis characterised by decreased ISC self-renewal, enteroblast differentiation defects and low enteroendocrine cell and enterocyte numbers. The ISC/enteroblast phenotypes result from a combination of cell autonomous and non-autonomous requirements for Cdk4 function. One non-autonomous consequence of Cdk4-dependent deficient enterocyte growth is high expression of Delta in ISCs and Delta retention in enteroblasts. We postulate that aberrant activation of the Delta–Notch pathway is a possible partial cause of lost ISC stemness. These results support the idea that enterocytes contribute to a putative stem cell niche that maintains intestinal homeostasis in the Drosophila anterior midgut.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 17-06-2008
DOI: 10.1126/SCISIGNAL.124PE30
Abstract: Mutations in the von Hippel-Lindau tumor suppressor gene VHL occur in various inherited and sporadically occurring tumors. The protein encoded by VHL —pVHL—bears no known enzymatic activities but interacts with numerous protein partners. With the identification of distinct pVHL-containing multiprotein complexes, a refined portrait of pVHL tumor suppressor function has arisen. In general, pVHL acts as a multipurpose adaptor protein that controls a erse array of gene expression programs, as well as extracellular matrix assembly and microtubule-based processes, by linking various target proteins to appropriate enzymatic activities. These findings provide an evermore complex but coherent view of how pVHL functions molecularly and of the consequences of dysregulation of these erse molecular activities on tumor formation.
Publisher: Informa UK Limited
Date: 04-2002
Publisher: Informa UK Limited
Date: 08-2007
DOI: 10.4161/CC.6.15.4518
Abstract: Amongst other clinical manifestations, patients with the von Hippel-Lindau (VHL) cancer syndrome are predisposed to develop kidney cysts, which are considered to be precursor lesions of clear cell renal cell carcinoma (ccRCC). Recent evidence has highlighted an unexpected function of the VHL tumor suppressor protein (pVHL) in maintaining the structural integrity of the primary cilium, a microtubule-based cellular antenna important for suppression of uncontrolled proliferation of kidney epithelial cells and cyst formation. Intriguingly, this function of pVHL is directly linked to its capacity to regulate the microtubule cytoskeleton independent of its well-characterized role in the degradation of hypoxia inducible factor alpha (HIFalpha) subunits. However, loss of pVHL alone does not suffice for a cell to lose the primary cilium. Other pathways need to be additionally inactivated, including one involving glycogen synthase kinase 3 beta (GSK3beta). These new findings draw attention to a primary cilium maintenance network as new territory for pVHL tumor suppressive activity and have implications for understanding the development of kidney pathology in the setting of VHL disease.
Publisher: Annual Reviews
Date: 24-01-2015
DOI: 10.1146/ANNUREV-PATHOL-012414-040306
Abstract: The von Hippel–Lindau (VHL) tumor suppressor gene is mutated as an early event in almost all cases of clear cell renal cell carcinoma (ccRCC), the most frequent form of kidney cancer. In this review we discuss recent advances in understanding how dysregulation of the many hypoxia-inducible factor α–dependent and –independent functions of the VHL tumor suppressor protein (pVHL) can contribute to tumor initiation and progression. Recent evidence showing extensive inter- and intratumoral genetic ersity has given rise to the idea that ccRCC should actually be considered as a series of molecularly related, yet distinct, diseases defined by the pattern of combinatorial genetic alterations present within the cells of the tumor. We highlight the range of genetic and epigenetic alterations that recur in ccRCC and discuss the mechanisms through which these events appear to function cooperatively with a loss of pVHL function in tumorigenesis.
Publisher: Wiley
Date: 08-1997
DOI: 10.1111/J.1440-1681.1997.TB02104.X
Abstract: 1. At any one instant, most receptors are now recognized to be able to stimulate multiple signal transduction pathways in a cell when activated by an appropriate hormone. These different signalling pathways appear to allow for distinct cellular responses, such as cell proliferation, differentiation, and shape change. 2. In addition, many different types of cell will possess the same type of receptor. Therefore, for a hormone to be able to transmit differential signals to the various cell types able to respond to it, cells must discriminate the stimulus at some point. Such discrimination would seem to be an absolute requirement to allow a tissue-specific response to an identical initial stimulus. In theory, this specificity could occur at many points in the receptor signal transduction cascade, including cytosolic receptor coupling systems and tissue/cell-specific responsive genes. 3. The present paper summarizes our work and that of others which has determined some of the coupling systems of G-protein-coupled receptors and tyrosine kinase receptors and how these systems may be interacting. 4. In addition to these theoretical considerations, a potential therapeutic strategy underlies the ability of receptors to couple to more than one signal transduction system. If a response to a hormone were, for ex le, either cell proliferation or cell morphological change or differentiation and separate receptor-coupled signalling systems were responsible for these effects, pharmacological intervention may allow the transfer from one signalling system to another. If such a change allowed a permanent change to the differentiated phenotype, this could potentially form the basis of a signal-based cancer therapy.
Publisher: American Society for Clinical Investigation
Date: 09-03-2015
DOI: 10.1172/JCI79743
Publisher: MDPI AG
Date: 07-04-2023
Abstract: Clear cell renal cell carcinoma (ccRCC) accounts for ~75% of kidney cancers. The biallelic inactivation of the von Hippel–Lindau tumor suppressor gene (VHL) is the truncal driver mutation of most cases of ccRCC. Cancer cells are metabolically reprogrammed and excrete modified nucleosides in larger amounts due to their increased RNA turnover. Modified nucleosides occur in RNAs and cannot be recycled by salvage pathways. Their potential as biomarkers has been demonstrated for breast or pancreatic cancer. To assess their suitability as biomarkers in ccRCC, we used an established murine ccRCC model, harboring Vhl, Trp53 and Rb1 (VPR) knockouts. Cell culture media of this ccRCC model and primary murine proximal tubular epithelial cells (PECs) were investigated by HPLC coupled to triple-quadrupole mass spectrometry using multiple-reaction monitoring. VPR cell lines were significantly distinguishable from PEC cell lines and excreted higher amounts of modified nucleosides such as pseudouridine, 5-methylcytidine or 2′-O-methylcytidine. The method’s reliability was confirmed in serum-starved VPR cells. RNA-sequencing revealed the upregulation of specific enzymes responsible for the formation of those modified nucleosides in the ccRCC model. These enzymes included Nsun2, Nsun5, Pus1, Pus7, Naf1 and Fbl. In this study, we identified potential biomarkers for ccRCC for validation in clinical trials.
Publisher: Springer Science and Business Media LLC
Date: 20-07-2009
DOI: 10.1038/NCB1912
Abstract: Error-free mitosis depends on fidelity-monitoring checkpoint systems that ensure correct temporal and spatial coordination of chromosome segregation by the microtubule spindle apparatus. Defects in these checkpoint systems can lead to genomic instability, an important aspect of tumorigenesis. Here we show that the von Hippel-Lindau (VHL) tumour suppressor protein, pVHL, which is inactivated in hereditary and sporadic forms of renal cell carcinoma, localizes to the mitotic spindle in mammalian cells and its functional inactivation provokes spindle misorientation, spindle checkpoint weakening and chromosomal instability. Spindle misorientation is linked to unstable astral microtubules and is supressed by the restoration of wild-type pVHL in pVHL-deficient cells, but not in naturally-occurring VHL disease mutants that are defective in microtubule stabilization. Impaired spindle checkpoint function and chromosomal instability are the result of reduced Mad2 (mitotic arrest deficient 2) levels actuated by pVHL-inactivation and are rescued by re-expression of either Mad2 or pVHL in VHL-defective cells. An association between VHL inactivation, reduced Mad2 levels and increased aneuploidy was also found in human renal cancer, implying that the newly identified functions of pVHL in promoting proper spindle orientation and chromosomal stability probably contribute to tumour suppression.
Publisher: Elsevier BV
Date: 09-2022
Publisher: MDPI AG
Date: 13-04-2021
Abstract: Oncogenic mutations in RAS family genes arise frequently in metastatic human cancers. Here we developed new mouse and cellular models of oncogenic HrasG12V-driven undifferentiated pleomorphic sarcoma metastasis and of KrasG12D-driven pancreatic ductal adenocarcinoma metastasis. Through analyses of these cells and of human oncogenic KRAS-, NRAS- and BRAF-driven cancer cell lines we identified that resistance to single MEK inhibitor and ERK inhibitor treatments arise rapidly but combination therapy completely blocks the emergence of resistance. The prior evolution of resistance to either single agent frequently leads to resistance to dual treatment. Dual MEK inhibitor plus ERK inhibitor therapy shows anti-tumor efficacy in an HrasG12V-driven autochthonous sarcoma model but features of drug resistance in vivo were also evident. Array-based kinome activity profiling revealed an absence of common patterns of signaling rewiring in single or double MEK and ERK inhibitor resistant cells, showing that the development of resistance to downstream signaling inhibition in oncogenic RAS-driven tumors represents a heterogeneous process. Nonetheless, in some single and double MEK and ERK inhibitor resistant cell lines we identified newly acquired drug sensitivities. These may represent additional therapeutic targets in oncogenic RAS-driven tumors and provide general proof-of-principle that therapeutic vulnerabilities of drug resistant cells can be identified.
Location: Switzerland
No related grants have been discovered for Ian Frew.