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Circumventing senescence is associated with stem cell properties and metformin sensitivity.

ABSTRACT: Most cancers arise in old individuals, which also accumulate senescent cells. Cellular senescence can be experimentally induced by expression of oncogenes or telomere shortening during serial passage in culture. In vivo, precursor lesions of several cancer types accumulate senescent cells, which are thought to represent a barrier to malignant progression and a response to the aberrant activation of growth signaling pathways by oncogenes (oncogene toxicity). Here, we sought to define gene expression changes associated with cells that bypass senescence induced by oncogenic RAS. In the context of pancreatic ductal adenocarcinoma (PDAC), oncogenic KRAS induces benign pancreatic intraepithelial neoplasias (PanINs), which exhibit features of oncogene-induced senescence. We found that the bypass of senescence in PanINs leads to malignant PDAC cells characterized by gene signatures of epithelial-mesenchymal transition, stem cells, and mitochondria. Stem cell properties were similarly acquired in PanIN cells treated with LPS, and in primary fibroblasts and mammary epithelial cells that bypassed Ras-induced senescence after reduction of ERK signaling. Intriguingly, maintenance of cells that circumvented senescence and acquired stem cell properties was blocked by metformin, an inhibitor of complex I of the electron transport chain or depletion of STAT3, a protein required for mitochondrial functions and stemness. Thus, our studies link bypass of senescence in premalignant lesions to loss of differentiation, acquisition of stemness features, and increased reliance on mitochondrial functions.

SUBMITTER: Deschenes-Simard X

PROVIDER: S-EPMC6413657 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Circumventing senescence is associated with stem cell properties and metformin sensitivity.

Deschênes-Simard Xavier X Parisotto Maxime M Rowell Marie-Camille MC Le Calvé Benjamin B Igelmann Sebastian S Moineau-Vallée Karine K Saint-Germain Emmanuelle E Kalegari Paloma P Bourdeau Véronique V Kottakis Filippos F Bardeesy Nabeel N Ferbeyre Gerardo G

Aging cell 20190106 2

Most cancers arise in old individuals, which also accumulate senescent cells. Cellular senescence can be experimentally induced by expression of oncogenes or telomere shortening during serial passage in culture. In vivo, precursor lesions of several cancer types accumulate senescent cells, which are thought to represent a barrier to malignant progression and a response to the aberrant activation of growth signaling pathways by oncogenes (oncogene toxicity). Here, we sought to define gene express ...[more]

PMID: 30614183

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Project description:Graphical abstract Our data suggest that metformin regulates the level of autophagosome-lysosome fusion leading to the upregulation of autophagic flux and significantly alleviates functional and structural changes associated with aging arteries, such as collagen accumulation and elastin damage. Metformin treatment also prevents a senescence-associated secretory phenotype (SASP) and improves the proliferation and migration of senescent VSMCs. Furthermore, disrupting the autophagosome-lysosome fusion abrogates the anti-senescence effects induced by metformin in VSMCs. Autophagy process is complex and involves multiple steps, it is unknown whether p62 mediated-selected autophagy seen in metformin treatment also contributes to activation of autophagic flux. Altogether, metformin, as an anti-aging drug, together with its novel role, as a regulator of autophagic flux, contributes to reduced senescence and SASP of VSMCs. Highlights • Metformin treatment improved functional and structural changes occur in aging arteries.• Metformin treatment prevented a senescence-associated secretory phenotype and improved the proliferation and migration of senescent VSMCs.• Reduced autophagic flux during cellular and vascular senescence was reversed by metformin.• Metformin enhances autophagy flux at the level of autophagosome-lysosome fusion via upregulating LAMP1. Introduction Vascular smooth muscle cell (VSMC) senescence in the vasculature results in vascular aging as well as age-related diseases, while metformin improves the inflamm-aging profile by enhancing autophagy. However, metformin’s impact on VSMC senescence is largely undefined. Objectives To test the hypothesis that metformin exerts an anti-senescence role by restoring autophagic activity in VSMCs and vascular tissues. Methods Animal models established by angiotensin II (Ang II) induction and physiological aging and senescent primary VSMCs from the aortas of elderly patients were treated with metformin. Cellular and vascular senescence were assessed by measuring the amounts of senescence-associated β-galactosidase and senescence markers, including p21 and p53. Autophagy levels were assessed by autophagy-related protein expression, transmission electron microscope, and autolysosome staining. In order to explore the underlying mechanism of the anti-senescence effects of metformin, 4D label-free quantitative proteomics and bioinformatic analyses were conducted, with subsequent experiments validating these findings. Results Ang II-dependent senescence was suppressed by metformin in VSMCs and vascular tissues. Metformin also significantly improved arterial stiffness and alleviated structural changes in aged arteries, reduced senescence-associated secretory phenotype (SASP), and improved proliferation and migration of senescent VSMCs. Mechanistically, the proteomic analysis indicated that autophagy might contribute to metformin’s anti-senescence effects. Reduced autophagic flux was observed in Ang II-induced cellular and vascular senescence; this reduction was reversed by metformin. Specifically, metformin enhanced the autophagic flux at the autophagosome-lysosome fusion level, whereas blockade of autophagosome-lysosome fusion inhibited the anti-senescence effects of metformin. Conclusions Metformin prevents VSMC and vascular senescence by promoting autolysosome formation.

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Circumventing senescence is associated with stem cell properties and metformin sensitivity.

Publications

Circumventing senescence is associated with stem cell properties and metformin sensitivity.

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