Publications by authors named "Laura Hulea"

22 Publications

  • Page 1 of 1

A hydride transfer complex reprograms NAD metabolism and bypasses senescence.

Mol Cell 2021 09;81(18):3848-3865.e19

CRCHUM, 900 Saint-Denis St, Montréal, QC H2X 0A9, Canada; Département de Biochimie et Médecine Moléculaire, Université de Montréal, Montréal, QC H3C 3J7, Canada. Electronic address:

Metabolic rewiring and redox balance play pivotal roles in cancer. Cellular senescence is a barrier for tumorigenesis circumvented in cancer cells by poorly understood mechanisms. We report a multi-enzymatic complex that reprograms NAD metabolism by transferring reducing equivalents from NADH to NADP. This hydride transfer complex (HTC) is assembled by malate dehydrogenase 1, malic enzyme 1, and cytosolic pyruvate carboxylase. HTC is found in phase-separated bodies in the cytosol of cancer or hypoxic cells and can be assembled in vitro with recombinant proteins. HTC is repressed in senescent cells but induced by p53 inactivation. HTC enzymes are highly expressed in mouse and human prostate cancer models, and their inactivation triggers senescence. Exogenous expression of HTC is sufficient to bypass senescence, rescue cells from complex I inhibitors, and cooperate with oncogenic RAS to transform primary cells. Altogether, we provide evidence for a new multi-enzymatic complex that reprograms metabolism and overcomes cellular senescence.
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http://dx.doi.org/10.1016/j.molcel.2021.08.028DOI Listing
September 2021

Selective inhibitors of mTORC1 activate 4EBP1 and suppress tumor growth.

Nat Chem Biol 2021 10 24;17(10):1065-1074. Epub 2021 Jun 24.

Program in Molecular Pharmacology, Department of Medicine, Memorial Sloan-Kettering Cancer Center (MSKCC), New York, NY, USA.

The clinical benefits of pan-mTOR active-site inhibitors are limited by toxicity and relief of feedback inhibition of receptor expression. To address these limitations, we designed a series of compounds that selectively inhibit mTORC1 and not mTORC2. These 'bi-steric inhibitors' comprise a rapamycin-like core moiety covalently linked to an mTOR active-site inhibitor. Structural modification of these components modulated their affinities for their binding sites on mTOR and the selectivity of the bi-steric compound. mTORC1-selective compounds potently inhibited 4EBP1 phosphorylation and caused regressions of breast cancer xenografts. Inhibition of 4EBP1 phosphorylation was sufficient to block cancer cell growth and was necessary for maximal antitumor activity. At mTORC1-selective doses, these compounds do not alter glucose tolerance, nor do they relieve AKT-dependent feedback inhibition of HER3. Thus, in preclinical models, selective inhibitors of mTORC1 potently inhibit tumor growth while causing less toxicity and receptor reactivation as compared to pan-mTOR inhibitors.
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http://dx.doi.org/10.1038/s41589-021-00813-7DOI Listing
October 2021

Perturbations of cancer cell metabolism by the antidiabetic drug canagliflozin.

Neoplasia 2021 04 27;23(4):391-399. Epub 2021 Mar 27.

Department of Biochemistry, McGill University, Montréal, QC, Canada; Departments of Biochemistry, Microbiology and Immunology, University of Ottawa, Ottawa, ON, Canada; Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON, Canada. Electronic address:

Notwithstanding that high rates of glucose uptake and glycolysis are common in neoplasia, pharmacological efforts to inhibit glucose utilization for cancer treatment have not been successful. Recent evidence suggests that in addition to classical glucose transporters, sodium-glucose transporters (SGLTs) are expressed by cancers. We therefore investigated the possibility that SGLT inhibitors, which are used in treatment of type 2 diabetes, may exert antineoplastic activity by limiting glucose uptake. We show that the SGLT2 inhibitor canagliflozin inhibits proliferation of breast cancer cells. Surprisingly, the antiproliferative effects of canagliflozin are not affected by glucose availability nor by the level of expression of SGLT2. Canagliflozin reduces oxygen consumption and glutamine metabolism through the citric acid cycle. The antiproliferative effects of canagliflozin are linked to inhibition of glutamine metabolism that fuels respiration, which represents a previously unanticipated mechanism of its potential antineoplastic action.
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http://dx.doi.org/10.1016/j.neo.2021.02.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8027095PMC
April 2021

PRDM15 is a key regulator of metabolism critical to sustain B-cell lymphomagenesis.

Nat Commun 2020 07 14;11(1):3520. Epub 2020 Jul 14.

Division of Cellular and Molecular Research, National Cancer Centre Singapore, Singapore, Singapore.

PRDM (PRDI-BF1 and RIZ homology domain containing) family members are sequence-specific transcriptional regulators involved in cell identity and fate determination, often dysregulated in cancer. The PRDM15 gene is of particular interest, given its low expression in adult tissues and its overexpression in B-cell lymphomas. Despite its well characterized role in stem cell biology and during early development, the role of PRDM15 in cancer remains obscure. Herein, we demonstrate that while PRDM15 is largely dispensable for mouse adult somatic cell homeostasis in vivo, it plays a critical role in B-cell lymphomagenesis. Mechanistically, PRDM15 regulates a transcriptional program that sustains the activity of the PI3K/AKT/mTOR pathway and glycolysis in B-cell lymphomas. Abrogation of PRDM15 induces a metabolic crisis and selective death of lymphoma cells. Collectively, our data demonstrate that PRDM15 fuels the metabolic requirement of B-cell lymphomas and validate it as an attractive and previously unrecognized target in oncology.
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http://dx.doi.org/10.1038/s41467-020-17064-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7360777PMC
July 2020

mTOR as a central regulator of lifespan and aging.

F1000Res 2019 2;8. Epub 2019 Jul 2.

Département de Biochimie et Médecine Moléculaire, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, QC, H3C 3J7, Canada.

The mammalian/mechanistic target of rapamycin (mTOR) is a key component of cellular metabolism that integrates nutrient sensing with cellular processes that fuel cell growth and proliferation. Although the involvement of the mTOR pathway in regulating life span and aging has been studied extensively in the last decade, the underpinning mechanisms remain elusive. In this review, we highlight the emerging insights that link mTOR to various processes related to aging, such as nutrient sensing, maintenance of proteostasis, autophagy, mitochondrial dysfunction, cellular senescence, and decline in stem cell function.
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http://dx.doi.org/10.12688/f1000research.17196.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6611156PMC
June 2020

METTL13 Methylation of eEF1A Increases Translational Output to Promote Tumorigenesis.

Cell 2019 01 3;176(3):491-504.e21. Epub 2019 Jan 3.

Department of Biology, Stanford University, Stanford, CA 94305, USA. Electronic address:

Increased protein synthesis plays an etiologic role in diverse cancers. Here, we demonstrate that METTL13 (methyltransferase-like 13) dimethylation of eEF1A (eukaryotic elongation factor 1A) lysine 55 (eEF1AK55me2) is utilized by Ras-driven cancers to increase translational output and promote tumorigenesis in vivo. METTL13-catalyzed eEF1A methylation increases eEF1A's intrinsic GTPase activity in vitro and protein production in cells. METTL13 and eEF1AK55me2 levels are upregulated in cancer and negatively correlate with pancreatic and lung cancer patient survival. METTL13 deletion and eEF1AK55me2 loss dramatically reduce Ras-driven neoplastic growth in mouse models and in patient-derived xenografts (PDXs) from primary pancreatic and lung tumors. Finally, METTL13 depletion renders PDX tumors hypersensitive to drugs that target growth-signaling pathways. Together, our work uncovers a mechanism by which lethal cancers become dependent on the METTL13-eEF1AK55me2 axis to meet their elevated protein synthesis requirement and suggests that METTL13 inhibition may constitute a targetable vulnerability of tumors driven by aberrant Ras signaling.
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http://dx.doi.org/10.1016/j.cell.2018.11.038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6499081PMC
January 2019

Translational and HIF-1α-Dependent Metabolic Reprogramming Underpin Metabolic Plasticity and Responses to Kinase Inhibitors and Biguanides.

Cell Metab 2018 12 20;28(6):817-832.e8. Epub 2018 Sep 20.

Lady Davis Institute, SMBD JGH, McGill University, Montreal, QC H3A 1A3, Canada; Gerald Bronfman Department of Oncology, McGill University, Montreal, QC H3A 1A3, Canada; Department of Biochemistry, McGill University, Montreal, QC H3A 1A3, Canada; Department of Experimental Medicine, McGill University, Montreal, QC H3A 1A3, Canada. Electronic address:

There is increasing interest in therapeutically exploiting metabolic differences between normal and cancer cells. We show that kinase inhibitors (KIs) and biguanides synergistically and selectively target a variety of cancer cells. Synthesis of non-essential amino acids (NEAAs) aspartate, asparagine, and serine, as well as glutamine metabolism, are major determinants of the efficacy of KI/biguanide combinations. The mTORC1/4E-BP axis regulates aspartate, asparagine, and serine synthesis by modulating mRNA translation, while ablation of 4E-BP1/2 substantially decreases sensitivity of breast cancer and melanoma cells to KI/biguanide combinations. Efficacy of the KI/biguanide combinations is also determined by HIF-1α-dependent perturbations in glutamine metabolism, which were observed in VHL-deficient renal cancer cells. This suggests that cancer cells display metabolic plasticity by engaging non-redundant adaptive mechanisms, which allows them to survive therapeutic insults that target cancer metabolism.
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http://dx.doi.org/10.1016/j.cmet.2018.09.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7252493PMC
December 2018

Oncogenic kinases and perturbations in protein synthesis machinery and energetics in neoplasia.

J Mol Endocrinol 2019 02;62(2):R83-R103

Lady Davis Institute, SMBD JGH, McGill University, Montreal, Quebec, Canada.

Notwithstanding that metabolic perturbations and dysregulated protein synthesis are salient features of cancer, the mechanism underlying coordination of cellular energy balance with mRNA translation (which is the most energy consuming process in the cell) is poorly understood. In this review, we focus on recently emerging insights in the molecular underpinnings of the cross-talk between oncogenic kinases, translational apparatus and cellular energy metabolism. In particular, we focus on the central signaling nodes that regulate these processes (e.g. the mechanistic/mammalian target of rapamycin MTOR) and the potential implications of these findings on improving the anti-neoplastic efficacy of oncogenic kinase inhibitors.
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http://dx.doi.org/10.1530/JME-18-0058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347283PMC
February 2019

mTOR Controls Mitochondrial Dynamics and Cell Survival via MTFP1.

Mol Cell 2017 Sep 14;67(6):922-935.e5. Epub 2017 Sep 14.

Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A1A3, Canada. Electronic address:

The mechanisms that link environmental and intracellular stimuli to mitochondrial functions, including fission/fusion, ATP production, metabolite biogenesis, and apoptosis, are not well understood. Here, we demonstrate that the nutrient-sensing mechanistic/mammalian target of rapamycin complex 1 (mTORC1) stimulates translation of mitochondrial fission process 1 (MTFP1) to control mitochondrial fission and apoptosis. Expression of MTFP1 is coupled to pro-fission phosphorylation and mitochondrial recruitment of the fission GTPase dynamin-related protein 1 (DRP1). Potent active-site mTOR inhibitors engender mitochondrial hyperfusion due to the diminished translation of MTFP1, which is mediated by translation initiation factor 4E (eIF4E)-binding proteins (4E-BPs). Uncoupling MTFP1 levels from the mTORC1/4E-BP pathway upon mTOR inhibition blocks the hyperfusion response and leads to apoptosis by converting mTOR inhibitor action from cytostatic to cytotoxic. These data provide direct evidence for cell survival upon mTOR inhibition through mitochondrial hyperfusion employing MTFP1 as a critical effector of mTORC1 to govern cell fate decisions.
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http://dx.doi.org/10.1016/j.molcel.2017.08.013DOI Listing
September 2017

mTOR-sensitive translation: Cleared fog reveals more trees.

RNA Biol 2017 10 10;14(10):1299-1305. Epub 2017 Feb 10.

a Department of Oncology-Pathology , Science for Life Laboratory, Karolinska Institutet , Stockholm , Sweden.

Translation is fundamental for many biologic processes as it enables cells to rapidly respond to stimuli without requiring de novo mRNA synthesis. The mammalian/mechanistic target of rapamycin (mTOR) is a key regulator of translation. Although mTOR affects global protein synthesis, translation of a subset of mRNAs appears to be exceptionally sensitive to changes in mTOR activity. Recent efforts to catalog these mTOR-sensitive mRNAs resulted in conflicting results. Whereas ribosome-profiling almost exclusively identified 5'-terminal oligopyrimidine (TOP) mRNAs as mTOR-sensitive, polysome-profiling suggested that mTOR also regulates translation of non-TOP mRNAs. This inconsistency was explained by analytical and technical biases limiting the efficiency of ribosome-profiling in detecting mRNAs showing differential translation. Moreover, genome-wide characterization of 5'UTRs of non-TOP mTOR-sensitive mRNAs revealed 2 subsets of transcripts which differ in their requirement for translation initiation factors and biologic functions. We summarize these recent advances and their impact on the understanding of mTOR-sensitive translation.
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http://dx.doi.org/10.1080/15476286.2017.1290041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5711451PMC
October 2017

The oncometabolite 2-hydroxyglutarate activates the mTOR signalling pathway.

Nat Commun 2016 09 14;7:12700. Epub 2016 Sep 14.

Département de Biochimie et Médecine Moléculaire, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, Quebec, Canada H3C 3J7.

The identification of cancer-associated mutations in the tricarboxylic acid (TCA) cycle enzymes isocitrate dehydrogenases 1 and 2 (IDH1/2) highlights the prevailing notion that aberrant metabolic function can contribute to carcinogenesis. IDH1/2 normally catalyse the oxidative decarboxylation of isocitrate into α-ketoglutarate (αKG). In gliomas and acute myeloid leukaemias, IDH1/2 mutations confer gain-of-function leading to production of the oncometabolite R-2-hydroxyglutarate (2HG) from αKG. Here we show that generation of 2HG by mutated IDH1/2 leads to the activation of mTOR by inhibiting KDM4A, an αKG-dependent enzyme of the Jumonji family of lysine demethylases. Furthermore, KDM4A associates with the DEP domain-containing mTOR-interacting protein (DEPTOR), a negative regulator of mTORC1/2. Depletion of KDM4A decreases DEPTOR protein stability. Our results provide an additional molecular mechanism for the oncogenic activity of mutant IDH1/2 by revealing an unprecedented link between TCA cycle defects and positive modulation of mTOR function downstream of the canonical PI3K/AKT/TSC1-2 pathway.
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http://dx.doi.org/10.1038/ncomms12700DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5027283PMC
September 2016

nanoCAGE reveals 5' UTR features that define specific modes of translation of functionally related MTOR-sensitive mRNAs.

Genome Res 2016 05 16;26(5):636-48. Epub 2016 Mar 16.

Lady Davis Institute, SMBD Jewish General Hospital, Montreal, Canada H3T 1E2; Department of Oncology, McGill University, Montreal, Canada H3G 1Y6; Department of Experimental Medicine, McGill University, Montreal, Canada H3G 1Y6; Department of Biochemistry, McGill University, Montreal, Canada H3G 1Y6;

The diversity of MTOR-regulated mRNA translation remains unresolved. Whereas ribosome-profiling suggested that MTOR almost exclusively stimulates translation of the TOP (terminal oligopyrimidine motif) and TOP-like mRNAs, polysome-profiling indicated that MTOR also modulates translation of mRNAs without the 5' TOP motif (non-TOP mRNAs). We demonstrate that in ribosome-profiling studies, detection of MTOR-dependent changes in non-TOP mRNA translation was obscured by low sensitivity and methodology biases. Transcription start site profiling using nano-cap analysis of gene expression (nanoCAGE) revealed that not only do many MTOR-sensitive mRNAs lack the 5' TOP motif but that 5' UTR features distinguish two functionally and translationally distinct subsets of MTOR-sensitive mRNAs: (1) mRNAs with short 5' UTRs enriched for mitochondrial functions, which require EIF4E but are less EIF4A1-sensitive; and (2) long 5' UTR mRNAs encoding proliferation- and survival-promoting proteins, which are both EIF4E- and EIF4A1-sensitive. Selective inhibition of translation of mRNAs harboring long 5' UTRs via EIF4A1 suppression leads to sustained expression of proteins involved in respiration but concomitant loss of those protecting mitochondrial structural integrity, resulting in apoptosis. Conversely, simultaneous suppression of translation of both long and short 5' UTR mRNAs by MTOR inhibitors results in metabolic dormancy and a predominantly cytostatic effect. Thus, 5' UTR features define different modes of MTOR-sensitive translation of functionally distinct subsets of mRNAs, which may explain the diverse impact of MTOR and EIF4A inhibitors on neoplastic cells.
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http://dx.doi.org/10.1101/gr.197566.115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4864462PMC
May 2016

Biomedical Potential of mTOR Modulation by Nanoparticles.

Trends Biotechnol 2016 05 15;34(5):349-353. Epub 2016 Feb 15.

Institute of Microbiology and Immunology, School of Medicine, University of Belgrade, Dr. Subotica 1, 11000 Belgrade, Serbia. Electronic address:

Modulation of the mammalian target of rapamycin (mTOR), the principal regulator of cellular homeostasis, underlies the biological effects of engineered nanoparticles, including regulation of cell death/survival and metabolic responses. Understanding the mechanisms and biological actions of nanoparticle-mediated mTOR modulation may help in developing safe and efficient nanotherapeutics to fight human disease.
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http://dx.doi.org/10.1016/j.tibtech.2016.01.005DOI Listing
May 2016

SBI-0640756 Attenuates the Growth of Clinically Unresponsive Melanomas by Disrupting the eIF4F Translation Initiation Complex.

Cancer Res 2015 Dec 24;75(24):5211-8. Epub 2015 Nov 24.

Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California.

Disrupting the eukaryotic translation initiation factor 4F (eIF4F) complex offers an appealing strategy to potentiate the effectiveness of existing cancer therapies and to overcome resistance to drugs such as BRAF inhibitors (BRAFi). Here, we identified and characterized the small molecule SBI-0640756 (SBI-756), a first-in-class inhibitor that targets eIF4G1 and disrupts the eIF4F complex. SBI-756 impaired the eIF4F complex assembly independently of mTOR and attenuated growth of BRAF-resistant and BRAF-independent melanomas. SBI-756 also suppressed AKT and NF-κB signaling, but small-molecule derivatives were identified that only marginally affected these pathways while still inhibiting eIF4F complex formation and melanoma growth, illustrating the potential for further structural and functional manipulation of SBI-756 as a drug lead. In the gene expression signature patterns elicited by SBI-756, DNA damage, and cell-cycle regulatory factors were prominent, with mutations in melanoma cells affecting these pathways conferring drug resistance. SBI-756 inhibited the growth of NRAS, BRAF, and NF1-mutant melanomas in vitro and delayed the onset and reduced the incidence of Nras/Ink4a melanomas in vivo. Furthermore, combining SBI-756 and a BRAFi attenuated the formation of BRAFi-resistant human tumors. Taken together, our findings show how SBI-756 abrogates the growth of BRAF-independent and BRAFi-resistant melanomas, offering a preclinical rationale to evaluate its antitumor effects in other cancers.
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http://dx.doi.org/10.1158/0008-5472.CAN-15-0885DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4681635PMC
December 2015

Targeting the translation machinery in cancer.

Nat Rev Drug Discov 2015 Apr 6;14(4):261-78. Epub 2015 Mar 6.

1] Lady Davis Institute for Medical Research, Jewish General Hospital, 3755 Côte-Ste-Catherine Road, Montreal, Quebec, H3T 1E2, Canada. [2] Department of Oncology, McGill University, 546 Pine Avenue West, Montreal, Quebec, H2W 1S6, Canada.

Dysregulation of mRNA translation is a frequent feature of neoplasia. Many oncogenes and tumour suppressors affect the translation machinery, making aberrant translation a widespread characteristic of tumour cells, independent of the genetic make-up of the cancer. Therefore, therapeutic agents that target components of the protein synthesis apparatus hold promise as novel anticancer drugs that can overcome intra-tumour heterogeneity. In this Review, we discuss the role of translation in cancer, with a particular focus on the eIF4F (eukaryotic translation initiation factor 4F) complex, and provide an overview of recent efforts aiming to 'translate' these results to the clinic.
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http://dx.doi.org/10.1038/nrd4505DOI Listing
April 2015

mTOR coordinates protein synthesis, mitochondrial activity and proliferation.

Cell Cycle 2015 ;14(4):473-80

a Department of Biochemistry and Goodman Cancer Research Centre ; McGill University ; Montreal , QC Canada.

Protein synthesis is one of the most energy consuming processes in the cell. The mammalian/mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that integrates a multitude of extracellular signals and intracellular cues to drive growth and proliferation. mTOR activity is altered in numerous pathological conditions, including metabolic syndrome and cancer. In addition to its well-established role in regulating mRNA translation, emerging studies indicate that mTOR modulates mitochondrial functions. In mammals, mTOR coordinates energy consumption by the mRNA translation machinery and mitochondrial energy production by stimulating synthesis of nucleus-encoded mitochondria-related proteins including TFAM, mitochondrial ribosomal proteins and components of complexes I and V. In this review, we highlight findings that link mTOR, mRNA translation and mitochondrial functions.
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http://dx.doi.org/10.4161/15384101.2014.991572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4615141PMC
December 2015

Serine deprivation enhances antineoplastic activity of biguanides.

Cancer Res 2014 Dec 6;74(24):7521-33. Epub 2014 Nov 6.

Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada. Department of Oncology, McGill University, Montreal, Quebec, Canada. Segal Cancer Center, Lady Davis Institute for Medical Research, Jewish General Hospital, Montreal, Quebec, Canada. Division of Cancer Prevention, McGill University, Montreal, Quebec, Canada.

Metformin, a biguanide widely used in the treatment of type II diabetes, clearly exhibits antineoplastic activity in experimental models and has been reported to reduce cancer incidence in diabetics. There are ongoing clinical trials to evaluate its antitumor properties, which may relate to its fundamental activity as an inhibitor of oxidative phosphorylation. Here, we show that serine withdrawal increases the antineoplastic effects of phenformin (a potent biguanide structurally related to metformin). Serine synthesis was not inhibited by biguanides. Instead, metabolic studies indicated a requirement for serine to allow cells to compensate for biguanide-induced decrease in oxidative phosphorylation by upregulating glycolysis. Furthermore, serine deprivation modified the impact of metformin on the relative abundance of metabolites within the citric acid cycle. In mice, a serine-deficient diet reduced serine levels in tumors and significantly enhanced the tumor growth-inhibitory actions of biguanide treatment. Our results define a dietary manipulation that can enhance the efficacy of biguanides as antineoplastic agents that target cancer cell energy metabolism.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-2643-TDOI Listing
December 2014

Autocrine Activation of the Wnt/β-Catenin Pathway by CUX1 and GLIS1 in Breast Cancers.

Biol Open 2014 Sep 12;3(10):937-46. Epub 2014 Sep 12.

Goodman Cancer Research Centre, McGill University, Montreal, QC H3A 1A3, Canada Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada Department of Medicine, McGill University, Montreal, QC H3A 1A1, Canada Department of Oncology, McGill University, Montreal, QC H2W 1S6, Canada

Autocrine activation of the Wnt/β-catenin pathway occurs in several cancers, notably in breast tumors, and is associated with higher expression of various Wnt ligands. Using various inhibitors of the FZD/LRP receptor complex, we demonstrate that some adenosquamous carcinomas that develop in MMTV-CUX1 transgenic mice represent a model for autocrine activation of the Wnt/β-catenin pathway. By comparing expression profiles of laser-capture microdissected mammary tumors, we identify Glis1 as a transcription factor that is highly expressed in the subset of tumors with elevated Wnt gene expression. Analysis of human cancer datasets confirms that elevated WNT gene expression is associated with high levels of CUX1 and GLIS1 and correlates with genes of the epithelial-to-mesenchymal transition (EMT) signature: VIM, SNAI1 and TWIST1 are elevated whereas CDH1 and OCLN are decreased. Co-expression experiments demonstrate that CUX1 and GLIS1 cooperate to stimulate TCF/β-catenin transcriptional activity and to enhance cell migration and invasion. Altogether, these results provide additional evidence for the role of GLIS1 in reprogramming gene expression and suggest a hierarchical model for transcriptional regulation of the Wnt/β-catenin pathway and the epithelial-to-mesenchymal transition.
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http://dx.doi.org/10.1242/bio.20148193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4197442PMC
September 2014

RAS transformation requires CUX1-dependent repair of oxidative DNA damage.

PLoS Biol 2014 Mar 11;12(3):e1001807. Epub 2014 Mar 11.

Goodman Cancer Centre, McGill University, Montreal, Quebec, Canada; Department of Biochemistry, McGill University, Montreal, Quebec, Canada; Department of Medicine, McGill University, Montreal, Quebec, Canada; Department of Oncology McGill University, Montreal, Quebec, Canada.

The Cut homeobox 1 (CUX1) gene is a target of loss-of-heterozygosity in many cancers, yet elevated CUX1 expression is frequently observed and is associated with shorter disease-free survival. The dual role of CUX1 in cancer is illustrated by the fact that most cell lines with CUX1 LOH display amplification of the remaining allele, suggesting that decreased CUX1 expression facilitates tumor development while increased CUX1 expression is needed in tumorigenic cells. Indeed, CUX1 was found in a genome-wide RNAi screen to identify synthetic lethal interactions with oncogenic RAS. Here we show that CUX1 functions in base excision repair as an ancillary factor for the 8-oxoG-DNA glycosylase, OGG1. Single cell gel electrophoresis (comet assay) reveals that Cux1⁺/⁻ MEFs are haploinsufficient for the repair of oxidative DNA damage, whereas elevated CUX1 levels accelerate DNA repair. In vitro base excision repair assays with purified components demonstrate that CUX1 directly stimulates OGG1's enzymatic activity. Elevated reactive oxygen species (ROS) levels in cells with sustained RAS pathway activation can cause cellular senescence. We show that elevated expression of either CUX1 or OGG1 prevents RAS-induced senescence in primary cells, and that CUX1 knockdown is synthetic lethal with oncogenic RAS in human cancer cells. Elevated CUX1 expression in a transgenic mouse model enables the emergence of mammary tumors with spontaneous activating Kras mutations. We confirmed cooperation between Kras(G12V) and CUX1 in a lung tumor model. Cancer cells can overcome the antiproliferative effects of excessive DNA damage by inactivating a DNA damage response pathway such as ATM or p53 signaling. Our findings reveal an alternate mechanism to allow sustained proliferation in RAS-transformed cells through increased DNA base excision repair capability. The heightened dependency of RAS-transformed cells on base excision repair may provide a therapeutic window that could be exploited with drugs that specifically target this pathway.
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http://dx.doi.org/10.1371/journal.pbio.1001807DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3949673PMC
March 2014

CUX1 transcription factors: from biochemical activities and cell-based assays to mouse models and human diseases.

Gene 2012 Apr 28;497(1):18-26. Epub 2012 Jan 28.

Goodman Cancer Centre, McGill University, 1160 Pine avenue West, Montreal, Quebec, Canada H3A 1A3.

ChIP-chip and expression analyses indicated that CUX1 transcription factors regulate a large number of genes and microRNAs involved in multiple cellular processes. Indeed, in proliferating cells CUX1 was shown to regulate several genes involved in DNA replication, progression into S phase and later, the spindle assembly checkpoint that controls progression through mitosis. siRNA-mediated knockdown established that CUX1 is required for cell motility. Moreover, higher expression of short CUX1 isoforms, as observed in many cancers, was shown to stimulate cell migration and invasion. In parallel, elevated expression particularly in higher grade tumors of breast and pancreatic cancers implicated CUX1 in tumor initiation and progression. Indeed, transgenic mouse models demonstrated a causal role of CUX1 in cancers originating from various cell types. These studies revealed that higher CUX1 expression or activity not only stimulates cell proliferation and motility, but also promotes genetic instability. CUX1 has also been implicated in the etiology of polycystic kidney diseases, both from a transgenic approach and the analysis of CUX1 activity in multiple mouse models of this disease. Studies in neurobiology have uncovered a potential implication of CUX1 in cognitive disorders, neurodegeneration and obesity. CUX1 was shown to be expressed specifically in pyramidal neurons of the neocortex upper layers where it regulates dendrite branching, spine development, and synapse formation. In addition, modulation of CUX1 expression in neurons of the hypothalamus has been associated with changes in leptin receptor trafficking in the vicinity of the primary cilium resulting in altered leptin signaling and ultimately, eating behavior. Overall, studies in various fields have allowed the development of several cell-based assays to monitor CUX1 function and have extended the range of organs in which CUX1 plays an important role in development and tissue homeostasis.
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http://dx.doi.org/10.1016/j.gene.2012.01.039DOI Listing
April 2012
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