André Bédard, Ph.D.
Research in my laboratory is centered on the study of cell proliferation and cell transformation. The control of gene expression in quiescent primary chicken embryo fibroblasts (CEF) is the focus of our current research program. In particular, we recently uncovered a novel response to the conditions of limited oxygen concentrations experienced by contact inhibited CEF and showed that this response is critical for the maintenance of lipid/membrane homeostasis and cell survival. Current investigations have for objective to characterize the cellular processes regulated by the lipid/membrane damage response promoting reversible growth arrest and survival of quiescent cells. To do this work we employ basic techniques of cell and molecular biology as well as genomic, proteomic and lipidomic approaches.
- Maslikowski, B.M., Wang, L., Wu, Y., Fielding, B. and Bédard, P.-A. (2017). JunD/AP-1 antagonizes the induction of DAPK1 to promote the survival of v-Src transformed cells. J. Virol. 91(1): e01925-16.
- Erb. M., Camacho, D., Xie, W., Maslikowski, B.M., Fielding, B., Ghosh, R., Poujade, F.-A., Athar, M., Assee, S., Mantella, L.-E., and Bédard, P.-A. (2016). Mol. Cell. Biol. 36: 2890-2902.
- Bassey-Archibong, B.I., kwiecien, J.M., Milosavljevic, S.B., Hallett, R.M., Rayner, L.G., Erb, M.J., Crawford-Brown, C.J., Stephenson, K.B., Bédard, P.-A., Hassell, J.A., and Daniel, J.M. (2016). Kaiso depletion attenuates transforming growth factor-b signaling and metastatic activity of triple-negative breast cancer cells. Oncogenesis 5:e208.
- Klionsky et al, (2016). Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12:1-222.
- Maynard, S., Ghosh, R., Wu, Y., Yan, S., Miyake, T., Gagliardi, M., Rethoret, K. and Bédard, P.-A. (2015). GABARAP is a determinant of apoptosis in growth-arrested chicken embryo fibroblasts. J. Cell. Physiol. 230: 1475-1488.
- Wang, L., Rodrigues, N.A., Wu, Y., Maslikowski, B., Singh, N., Lacroix, S. and Bédard, P.-A. (2011). Pleiotropic action of AP-1 in v-Src transformed cells. J. Virol. 85:6725-6735.
- Maslikowski, B., Néel, B.D., Wu, Y., Wang. L., Rodrigues, N.A., Gillet, G. and Bédard, P.-A. (2010). Cellular processes of v-Src transformation revealed by gene profiling of primary cells – Implications for human cancer. BMC Cancer 10:41
- Papaconstantinou, M., Pepper, A.N., Wu, Y., Kasimer, D., Westwood, T., Campos, A.R. and Bédard, P.-A. (2010). Menin links the stress response to genome stability. PLoS One 5:e14049.
- Papaconstantinou, M, Maslikowski, B., Pepper, A.N. and Bédard, P.-A. (2009). Menin, the protein behind the MEN1 syndrome. Adv. Experim. Med. Bio, 668:26-36 (review).
- Grondin, B., Lefrançois, M., Tremblay, M., Saint-Denis, M., Haman, A.,Bédard, P.-A., Tenen, D.G., and Hoang, T. 2007. c-Jun homodimers can function as a context-specific coactivator. Mol. Cell. Biol. 27: 2919-2933
- Campos, C.B.L., Bédard, P.-A. and Linden, R. (2006). Requirement of p38 stress-activated MAP kinase for cell death in the developing retina depends on the stage of cell differentiation. Neurochem. Int. 49:494-499
- Papaconstantinou, M., Wu, Y., Singh, N., Gianfelice,G., Tanguay, R.M., Campos, A.R. and P.-A. Bédard. (2005). Menin is a regulator of the stress response in Drosophila melanogaster. Mol. Cell. Biol. 25: 9960-9972
- Campos, C.B., P.-A. Bédard and R. Linden. (2003). Selective involvement of the PI3K/PKB/bad pathway in retinal cell death. J. Neurobiol. 56: 171-177.
- Gagliardi, M., Maynard, S., Miyake T., Rodrigues N., Tjew S.-L., Cabannes E. and P.-A. Bédard. (2003). Opposing roles of C/EBPb and AP-1 in the control of fibroblast proliferation and growth-arrest specific gene expression. J. Biol. Chem. 278: 43846-43854.
- Campos, CB, Bédard, P.-A. and Linden, R. Activation of p38 mitogen-activated protein kinase during normal mitosis in the developing retina . Neuroscience 112: 583-591 (2002).
- Gagliardi, M., Maynard, S., Bojovic, B. and Bédard, P.-A. The constitutive activation of the CEF-4/9E3 chemokine gene depends on C/EBPb in v-src transformed chicken embryo fibroblasts. Oncogene 20: 2301-2313 (2001).
- Kim, S., Mao, P.L., Gagliardi, M. and Bédard, P.-A. C/EBPb (NF-M) is essential for activation of the p20K lipocalin gene in growth-arrested chicken embryo fibroblasts. Mol Cell. Biol. 19: 5718-5731 (1999).
- Cabannes, E., Vives, M.-F. and Bédard, P.-A. (1997). Transcriptional and post-transcriptional regulation of KappaB-controlled genes by pp60v-src.Oncogene 15: 29-43(1997).
- Bojovic, B., Rodrigues, N., Dehbi, M. and Bédard, P.-A. Multiple signaling pathways control the activation of the CEF-4/9E3 cytokine gene by pp60v-src.J. Biol. Chem. 271: 22528-22537 (1996).
The research in our laboratory is focused on the control of cell proliferation and transformation. Primary fibroblasts isolated from chicken embryo (chicken embryo fibroblasts or CEFs) are our favorite model of investigation. While we have extensively studied transformation by the viral Src oncogene in the past (see Maslikowski et al, 2017, for a recent publication), our current focus is on biological processes of quiescent cells and, particularly, cells in a state of reversible growth arrest. In these conditions, cells do not divide but have the capacity to reenter the cell cycle in response to mitogenic stimulation and favorable growth conditions. Quiescence can be established in conditions of limiting nutrient and growth factor availability (starvation) or when normal adherent cells reach confluence in vitro, a process known as contact inhibition. While starvation is essentially a stress response rarely encountered in physiological conditions in vivo, contact inhibition is part of the normal wound healing process and for this reason is studied preferentially in our laboratory.
Gene profiling studies revealed that contact inhibition is characterized by the activation of genes expressed in conditions of limiting oxygen concentrations (hypoxia), genes regulating lipid metabolism and genes involved in cell signaling. Using fluorescence probes sensitive to oxygen levels, we confirmed recently that hypoxia is a feature of contact inhibition and a key determinant of growth arrest (Erb, M. et al, 2016). Paradoxically, cells in hypoxia release intracellular reactive oxygen species (ROS), which may attack several molecular species in the cell (DNA, RNA, proteins, lipids). Using RNA interference, we showed recently that the function of the p20K lipocalin, a key target of the gene expression program of contact inhibited cells, is to promote lipid and membrane integrity. Thus, interfering with p20K expression in contact inhibited cells results in increased lipid peroxidation and cell death (apoptosis; Erb and Bédard, in preparation). Since several genes activated at contact inhibition encode a lipid-binding protein or regulator of lipid metabolism, we believe that contact inhibited CEF express a novel program promoting membrane homeostasis and cell survival. Characterizing this novel response is the focus of ongoing research in the laboratory.
In a parallel study, lipid profiling of actively dividing and contact inhibited cells revealed that several fatty acids and cholesterol accumulate in quiescent cells. Since several of these lipid species such as palmitate, stearate or arachidonate are toxic for the cell, these observations are consistent with the notion that genes activated at contact inhibition have for function to restore lipid/membrane homeostasis. Comprehensive lipidomic analyses are ongoing to characterize this process and identify novel lipid species regulated during reversible growth arrest.
Finally, we also observed that contact inhibited CEFs release vesicles known as exosomes in the extracellular environment. Exosomes deliver regulatory proteins, mRNAs and miRNAs modulating the physiology and behaviour of cells of the microenvironment. The purification and functional characterization of exosomes is also a focus of the laboratory. In preliminary studies, we observed that the signaling kinase “Protein Kinase C Eta” (PKCη) is enriched in exosomes. PKCη is unique among PKC enzymes because it is activated by derivatives of cholesterol, such as 3’sulfo-cholesterol. Since Sulfotransferase 1E1, the enzyme promoting sulfatation of cholesterol, is also strongly induced by contact inhibition, several components of a signaling pathway involving cholesterol are induced in response to reversible growth arrest. Characterizing this signaling pathway represents an additional avenue of research in the laboratory.
In summary, our current research program has for objective to characterize novel pathways and biological processes promoting cell survival and ensuring reversible growth arrest in quiescent cells. A particular focus of our group is the characterization of the novel “Lipid Damage/Membrane Stress” response recently identified in our laboratory.