Publications by authors named "Gaelle Bridon"

13 Publications

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Glucose-dependent partitioning of arginine to the urea cycle protects β-cells from inflammation.

Nat Metab 2020 05 11;2(5):432-446. Epub 2020 May 11.

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.

Chronic inflammation is linked to diverse disease processes, but the intrinsic mechanisms that determine cellular sensitivity to inflammation are incompletely understood. Here, we show the contribution of glucose metabolism to inflammation-induced changes in the survival of pancreatic islet β-cells. Using metabolomic, biochemical and functional analyses, we investigate the protective versus non-protective effects of glucose in the presence of pro-inflammatory cytokines. When protective, glucose metabolism augments anaplerotic input into the TCA cycle via pyruvate carboxylase (PC) activity, leading to increased aspartate levels. This metabolic mechanism supports the argininosuccinate shunt, which fuels ureagenesis from arginine and conversely diminishes arginine utilization for production of nitric oxide (NO), a chief mediator of inflammatory cytotoxicity. Activation of the PC-urea cycle axis is sufficient to suppress NO synthesis and shield cells from death in the context of inflammation and other stress paradigms. Overall, these studies uncover a previously unappreciated link between glucose metabolism and arginine-utilizing pathways via PC-directed ureagenesis as a protective mechanism.
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http://dx.doi.org/10.1038/s42255-020-0199-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7568475PMC
May 2020

Repression of LKB1 by Sensitizes -Dependent Lymphoma to Biguanide Treatment.

Cell Rep Med 2020 May 19;1(2):100014. Epub 2020 May 19.

Goodman Cancer Research Centre, McGill University, Montreal, QC H3A 1A3, Canada.

Cancer cells display metabolic plasticity to survive stresses in the tumor microenvironment. Cellular adaptation to energetic stress is coordinated in part by signaling through the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathway. Here, we demonstrate that miRNA-mediated silencing of LKB1 confers sensitivity of lymphoma cells to mitochondrial inhibition by biguanides. Using both classic (phenformin) and newly developed (IM156) biguanides, we demonstrate that elevated expression in lymphoma cells promotes increased apoptosis to biguanide treatment and . This effect is driven by the -dependent silencing of LKB1, which reduces AMPK activation in response to complex I inhibition. Mechanistically, biguanide treatment induces metabolic stress in lymphoma cells by inhibiting TCA cycle metabolism and mitochondrial respiration, exposing metabolic vulnerability. Finally, we demonstrate a direct correlation between expression and biguanide sensitivity in human cancer cells. Our results identify expression as a potential biomarker for biguanide sensitivity in malignancies.
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http://dx.doi.org/10.1016/j.xcrm.2020.100014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7249503PMC
May 2020

Methotrexate elicits pro-respiratory and anti-growth effects by promoting AMPK signaling.

Sci Rep 2020 05 12;10(1):7838. Epub 2020 May 12.

Department of Biochemistry, McGill University, Montréal, QC, H3G 1Y6, Canada.

One-carbon metabolism fuels the high demand of cancer cells for nucleotides and other building blocks needed for increased proliferation. Although inhibitors of this pathway are widely used to treat many cancers, their global impact on anabolic and catabolic processes remains unclear. Using a combination of real-time bioenergetics assays and metabolomics approaches, we investigated the global effects of methotrexate on cellular metabolism. We show that methotrexate treatment increases the intracellular concentration of the metabolite AICAR, resulting in AMPK activation. Methotrexate-induced AMPK activation leads to decreased one-carbon metabolism gene expression and cellular proliferation as well as increased global bioenergetic capacity. The anti-proliferative and pro-respiratory effects of methotrexate are AMPK-dependent, as cells with reduced AMPK activity are less affected by methotrexate treatment. Conversely, the combination of methotrexate with the AMPK activator, phenformin, potentiates its anti-proliferative activity in cancer cells. These data highlight a reciprocal effect of methotrexate on anabolic and catabolic processes and implicate AMPK activation as a metabolic determinant of methotrexate response.
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http://dx.doi.org/10.1038/s41598-020-64460-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7217946PMC
May 2020

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

Leveraging increased cytoplasmic nucleoside kinase activity to target mtDNA and oxidative phosphorylation in AML.

Blood 2017 05 10;129(19):2657-2666. Epub 2017 Mar 10.

Princess Margaret Cancer Centre, Toronto, ON, Canada.

Mitochondrial DNA (mtDNA) biosynthesis requires replication factors and adequate nucleotide pools from the mitochondria and cytoplasm. We performed gene expression profiling analysis of 542 human acute myeloid leukemia (AML) samples and identified 55% with upregulated mtDNA biosynthesis pathway expression compared with normal hematopoietic cells. Genes that support mitochondrial nucleotide pools, including mitochondrial nucleotide transporters and a subset of cytoplasmic nucleoside kinases, were also increased in AML compared with normal hematopoietic samples. Knockdown of cytoplasmic nucleoside kinases reduced mtDNA levels in AML cells, demonstrating their contribution in maintaining mtDNA. To assess cytoplasmic nucleoside kinase pathway activity, we used a nucleoside analog 2'3'-dideoxycytidine (ddC), which is phosphorylated to the activated antimetabolite, 2'3'-dideoxycytidine triphosphate by cytoplasmic nucleoside kinases. ddC is a selective inhibitor of the mitochondrial DNA polymerase γ. ddC was preferentially activated in AML cells compared with normal hematopoietic progenitor cells. ddC treatment inhibited mtDNA replication, oxidative phosphorylation, and induced cytotoxicity in a panel of AML cell lines. Furthermore, ddC preferentially inhibited mtDNA replication in a subset of primary human leukemia cells and selectively targeted leukemia cells while sparing normal progenitor cells. In animal models of human AML, treatment with ddC decreased mtDNA, electron transport chain proteins, and induced tumor regression without toxicity. ddC also targeted leukemic stem cells in secondary AML xenotransplantation assays. Thus, AML cells have increased cytidine nucleoside kinase activity that regulates mtDNA biogenesis and can be leveraged to selectively target oxidative phosphorylation in AML.
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http://dx.doi.org/10.1182/blood-2016-10-741207DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5766841PMC
May 2017

The PGC-1α/ERRα Axis Represses One-Carbon Metabolism and Promotes Sensitivity to Anti-folate Therapy in Breast Cancer.

Cell Rep 2016 Feb 21;14(4):920-931. Epub 2016 Jan 21.

Goodman Cancer Research Centre, McGill University, Montréal, QC H3A 1A3, Canada; Department of Biochemistry, McGill University, Montréal, QC H3G 1Y6, Canada. Electronic address:

Reprogramming of cellular metabolism plays a central role in fueling malignant transformation, and AMPK and the PGC-1α/ERRα axis are key regulators of this process. The intersection of gene-expression and binding-event datasets for breast cancer cells shows that activation of AMPK significantly increases the expression of PGC-1α/ERRα and promotes the binding of ERRα to its cognate sites. Unexpectedly, the data also reveal that ERRα, in concert with PGC-1α, negatively regulates the expression of several one-carbon metabolism genes, resulting in substantial perturbations in purine biosynthesis. This PGC-1α/ERRα-mediated repression of one-carbon metabolism promotes the sensitivity of breast cancer cells and tumors to the anti-folate drug methotrexate. These data implicate the PGC-1α/ERRα axis as a core regulatory node of folate cycle metabolism and further suggest that activators of AMPK could be used to modulate this pathway in cancer.
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http://dx.doi.org/10.1016/j.celrep.2015.12.086DOI Listing
February 2016

Mitochondrial Phosphoenolpyruvate Carboxykinase Regulates Metabolic Adaptation and Enables Glucose-Independent Tumor Growth.

Mol Cell 2015 Oct;60(2):195-207

Goodman Cancer Research Centre, McGill University, Montreal, QC H3A 1A3, Canada; Department of Physiology, McGill University, Montreal, QC H3G 1Y6, Canada. Electronic address:

Cancer cells adapt metabolically to proliferate under nutrient limitation. Here we used combined transcriptional-metabolomic network analysis to identify metabolic pathways that support glucose-independent tumor cell proliferation. We found that glucose deprivation stimulated re-wiring of the tricarboxylic acid (TCA) cycle and early steps of gluconeogenesis to promote glucose-independent cell proliferation. Glucose limitation promoted the production of phosphoenolpyruvate (PEP) from glutamine via the activity of mitochondrial PEP-carboxykinase (PCK2). Under these conditions, glutamine-derived PEP was used to fuel biosynthetic pathways normally sustained by glucose, including serine and purine biosynthesis. PCK2 expression was required to maintain tumor cell proliferation under limited-glucose conditions in vitro and tumor growth in vivo. Elevated PCK2 expression is observed in several human tumor types and enriched in tumor tissue from non-small-cell lung cancer (NSCLC) patients. Our results define a role for PCK2 in cancer cell metabolic reprogramming that promotes glucose-independent cell growth and metabolic stress resistance in human tumors.
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http://dx.doi.org/10.1016/j.molcel.2015.08.013DOI Listing
October 2015

Synergy between the NAMPT inhibitor GMX1777(8) and pemetrexed in non-small cell lung cancer cells is mediated by PARP activation and enhanced NAD consumption.

Cancer Res 2014 Nov 21;74(21):5948-54. Epub 2014 Aug 21.

Laboratory for Therapeutic Development, McGill University, Montreal, Québec, Canada.

GMX1778 and its prodrug GMX1777 represent a new class of cancer drugs that targets nicotinamide phosphoribosyltransferase (NAMPT) as a new strategy to interfere with biosynthesis of the key enzymatic cofactor NAD, which is critical for a number of cell functions, including DNA repair. Using a genome-wide synthetic lethal siRNA screen, we identified the folate pathway-related genes, deoxyuridine triphosphatase and dihydrofolate reductase, the silencing of which sensitized non-small cell lung carcinoma (NSCLC) cells to the cytotoxic effects of GMX. Pemetrexed is an inhibitor of dihydrofolate reductase currently used to treat patients with nonsquamous NSCLC. We found that combining pemetrexed with GMX1777 produced a synergistic therapeutic benefit in A549 and H1299 NSCLC cells in vitro and in a mouse A549 xenograft model of lung cancer. Pemetrexed is known to activate PARPs, thereby accelerating NAD consumption. Genetic or pharmacologic blockade of PARP activity inhibited this effect, impairing cell death by pemetrexed either alone or in combination with GMX1777. Conversely, inhibiting the base excision repair pathway accentuated NAD decline in response to GMX and the cytotoxicity of both agents either alone or in combination. These findings provide a mechanistic rationale for combining GMX1777 with pemetrexed as an effective new therapeutic strategy to treat nonsquamous NSCLC.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-0809DOI Listing
November 2014

LKB1 is a central regulator of tumor initiation and pro-growth metabolism in ErbB2-mediated breast cancer.

Cancer Metab 2013 Aug 14;1(1):18. Epub 2013 Aug 14.

Goodman Cancer Research Centre, McGill University, Montréal, Québec, Canada.

Background: Germline and somatic mutations in STK11, the gene encoding the serine/threonine kinase LKB1, are strongly associated with tumorigenesis. While loss of LKB1 expression has been linked to breast cancer, the mechanistic role of LKB1 in regulating breast cancer development, metastasis, and tumor metabolism has remained unclear.

Methods: We have generated and analyzed transgenic mice expressing ErbB2 in the mammary epithelium of LKB1 wild-type or LKB1-deficient mice. We have also utilized ErbB2-expressing breast cancer cells in which LKB1 levels have been reduced using shRNA approaches. These transgenic and xenograft models were characterized for the effects of LKB1 loss on tumor initiation, growth, metastasis and tumor cell metabolism.

Results: We demonstrate that loss of LKB1 promotes tumor initiation and induces a characteristic shift to aerobic glycolysis ('Warburg effect') in a model of ErbB2-mediated breast cancer. LKB1-deficient breast cancer cells display enhanced early tumor growth coupled with increased cell migratory and invasive properties in vitro. We show that ErbB2-positive tumors deficient for LKB1 display a pro-growth molecular and phenotypic signature characterized by elevated Akt/mTOR signaling, increased glycolytic metabolism, as well as increased bioenergetic markers both in vitro and in vivo. We also demonstrate that mTOR contributes to the metabolic reprogramming of LKB1-deficient breast cancer, and is required to drive glycolytic metabolism in these tumors; however, LKB1-deficient breast cancer cells display reduced metabolic flexibility and increased apoptosis in response to metabolic perturbations.

Conclusions: Together, our data suggest that LKB1 functions as a tumor suppressor in breast cancer. Loss of LKB1 collaborates with activated ErbB2 signaling to drive breast tumorigenesis and pro-growth metabolism in the resulting tumors.
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http://dx.doi.org/10.1186/2049-3002-1-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4178213PMC
August 2013

The eEF2 kinase confers resistance to nutrient deprivation by blocking translation elongation.

Cell 2013 May;153(5):1064-79

Department of Molecular Oncology, British Columbia Cancer Research Centre, University of British Columbia (UBC), Vancouver, BC V5Z1L4, Canada.

Metabolic adaptation is essential for cell survival during nutrient deprivation. We report that eukaryotic elongation factor 2 kinase (eEF2K), which is activated by AMP-kinase (AMPK), confers cell survival under acute nutrient depletion by blocking translation elongation. Tumor cells exploit this pathway to adapt to nutrient deprivation by reactivating the AMPK-eEF2K axis. Adaptation of transformed cells to nutrient withdrawal is severely compromised in cells lacking eEF2K. Moreover, eEF2K knockdown restored sensitivity to acute nutrient deprivation in highly resistant human tumor cell lines. In vivo, overexpression of eEF2K rendered murine tumors remarkably resistant to caloric restriction. Expression of eEF2K strongly correlated with overall survival in human medulloblastoma and glioblastoma multiforme. Finally, C. elegans strains deficient in efk-1, the eEF2K ortholog, were severely compromised in their response to nutrient depletion. Our data highlight a conserved role for eEF2K in protecting cells from nutrient deprivation and in conferring tumor cell adaptation to metabolic stress. PAPERCLIP:
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http://dx.doi.org/10.1016/j.cell.2013.04.055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4395874PMC
May 2013

Occurrence and detection of phosphopeptide isomers in large-scale phosphoproteomics experiments.

J Proteome Res 2012 Jul 22;11(7):3753-65. Epub 2012 Jun 22.

IRIC, Institute for Research in Immunology and Cancer, Université de Montréal, P.O. Box 6128, Station Centre-ville, Montréal, Québec, Canada H3C 3J7.

The past decade has been marked by the emergence of selective affinity media and sensitive mass spectrometry instrumentation that facilitated large-scale phosphoproteome analyses and expanded the repertoire of protein phosphorylation. Despite these remarkable advances, the precise location of the phosphorylation site still represents a sizable challenge in view of the labile nature of the phosphoester bond and the presence of neighboring phosphorylatable residues within the same peptide. This difficulty is exacerbated by the combinatorial distribution of phosphorylated residues giving rise to different phosphopeptide isomers. These peptides have similar physicochemical properties, and their separation by LC is often problematic. Few studies have described the frequency and distribution of phosphoisomers in large-scale phosphoproteomics experiments, and no convenient informatics tools currently exist to facilitate their detection. To address this analytical challenge, we developed two algorithms to detect separated and co-eluting phosphopeptide isomers and target their subsequent identification using an inclusion list in LC-MS/MS experiments. Using these algorithms, we determined that the proportion of isomers present in phosphoproteomics studies from mouse, rat, and fly cell extracts represents 3-6% of all identified phosphopeptides. While conventional analysis can identify chromatographically separated phosphopeptides, targeted LC-MS/MS analyses using inclusion lists provided complementary identification and expanded the number of phosphopeptide isomers by at least 52%. Interestingly, these analyses revealed that the occurrence of phosphopeptides isomers can also correlate with the presence of extended phosphorylatable amino acids that can act as a "phosphorylation switch" to bind complementary domains such as those present in SR proteins and ribonucleoprotein complexes.
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http://dx.doi.org/10.1021/pr300229mDOI Listing
July 2012

Improvement of phosphoproteome analyses using FAIMS and decision tree fragmentation. application to the insulin signaling pathway in Drosophila melanogaster S2 cells.

J Proteome Res 2012 Feb 1;11(2):927-40. Epub 2011 Dec 1.

Institute for Research in Immunology and Cancer, Université de Montréal , P.O. Box 6128, Station, Centre-ville, Montréal, Québec, Canada H3C 3J7.

This report examines the analytical benefits of high-field asymmetric waveform ion mobility spectrometry (FAIMS) coupled to liquid chromatography mass spectrometry (LC-MS) for phosphoproteomics analyses. The ability of FAIMS to separate multiply charged peptide ions from chemical interferences confers a unique advantage in phosphoproteomics by enhancing the detection of low abundance phosphopeptides. LC-FAIMS-MS experiments performed on TiO(2)-enriched tryptic digests from Drosophila melanogaster provided a 50% increase in phosphopeptide identification compared to conventional LC-MS analysis. Also, FAIMS can be used to select different population of multiply charged phosphopeptide ions prior to their activation with either collision activated dissociation (CAD) or electron transfer dissociation (ETD). Importantly, FAIMS enabled the resolution of coeluting phosphoisomers of different abundances to facilitate their unambiguous identification using conventional database search engines. The benefits of FAIMS in large-scale phosphoproteomics of D. melanogaster are further investigated using label-free quantitation to identify differentially regulated phosphoproteins in response to insulin stimulation.
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http://dx.doi.org/10.1021/pr200722sDOI Listing
February 2012

Subcellular phosphoproteomics.

Mass Spectrom Rev 2010 Nov-Dec;29(6):962-90

Institute for Research in Immunology and Cancer, Université de Montréal, P.O. Box 6128, Station Centre-ville, Montréal, Québec, Canada H3C 3J7.

Protein phosphorylation represents one of the most extensively studied post-translational modifications, primarily due to the emergence of sensitive methods enabling the detection of this modification both in vitro and in vivo. The availability of enrichment methods combined with sensitive mass spectrometry instrumentation has played a crucial role in uncovering the dynamic changes and the large expanding repertoire of this reversible modification. The structural changes imparted by the phosphorylation of specific residues afford exquisite mechanisms for the regulation of protein functions by modulating new binding sites on scaffold proteins or by abrogating protein-protein interactions. However, the dynamic interplay of protein phosphorylation is not occurring randomly within the cell but is rather finely orchestrated by specific kinases and phosphatases that are unevenly distributed across subcellular compartments. This spatial separation not only regulates protein phosphorylation but can also control the activity of other enzymes and the transfer of other post-translational modifications. While numerous large-scale phosphoproteomics studies highlighted the extent and diversity of phosphoproteins present in total cell lysates, the further understanding of their regulation and biological activities require a spatio-temporal resolution only achievable through subcellular fractionation. This review presents a first account of the emerging field of subcellular phosphoproteomics where cell fractionation approaches are combined with sensitive mass spectrometry methods to facilitate the identification of low abundance proteins and to unravel the intricate regulation of protein phosphorylation.
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http://dx.doi.org/10.1002/mas.20297DOI Listing
February 2011
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