Mir-34a-5p Mediates Cross-Talk between M2 Muscarinic Receptors and Notch-1/EGFR Pathways in U87MG Glioblastoma Cells: Implication in Cell Proliferation

Abstract

Glioblastoma (GBM) is the most aggressive human brain tumor. The high growth potential and decreased susceptibility to apoptosis of the glioma cells is mainly dependent on genetic amplifications or mutations of oncogenic or pro-apoptotic genes, respectively. We have previously shown that the activation of the M2 acetylcholine muscarinic receptors inhibited cell proliferation and induced apoptosis in two GBM cell lines and cancer stem cells. The aim of this study was to delve into the molecular mechanisms underlying the M2-mediated cell proliferation arrest. Exploiting U87MG and U251MG cell lines as model systems, we evaluated the ability of M2 receptors to interfere with Notch-1 and EGFR pathways, whose activation promotes GBM proliferation. We demonstrated that the activation of M2 receptors, by agonist treatment, counteracted Notch and EGFR signaling, through different regulatory cascades depending, at least in part, on p53 status. Only in U87MG cells, which mimic p53-wild type GBMs, did M2 activation trigger a molecular circuitry involving p53, Notch-1, and the tumor suppressor mir-34a-5p. This regulatory module negatively controls Notch-1, which affects cell proliferation mainly through the Notch-1/EGFR axis. Our data highlighted, for the first time, a molecular circuitry that is deregulated in the p53 wild type GBM, based on the cross-talk between M2 receptor and the Notch-1/EGFR pathways, mediated by mir-34a-5p.

Cross Interaction between M2 Muscarinic Receptor and Notch1/EGFR Pathway in Human Glioblastoma Cancer Stem Cells: Effects on Cell Cycle Progression and Survival

“…Notch1 positively regulates EGFR transcription [10,32]; therefore, the downregulation of EGFR observed in GB7 cells could also be explained through APE-induced Notch-1 downregulation. The role played by Notch and EGFR in GSCs proliferation might be relevant.…”

Long non-coding RNA HOTAIR drives EZH2-dependent myofibroblast activation in systemic sclerosis through miRNA 34a-dependent activation of NOTCH

“…On ligand binding, the receptor is cleaved by gamma secretase proteases to release the intracellular domain Notch Intracellular Domain (NID),14 which induces transcription of downstream targets 15. NOTCH expression is known to be regulated by miRNAs such as miRNA-34a, which function as a suppressor of NOTCH expression 16 17…”

RETRACTED ARTICLE: The Notch signal mediates macrophage polarization by regulating miR-125a/miR-99b expression

“…As a highly conserved signalling pathway regulating cell differentiation and development, the Notch pathway widely participates in the onset and progression of various diseases. During the onset and progression of tumours, Notch signal acts on epithelial-mesenchymal transition, angiogenesis, apoptosis and stem cell proliferation [6], and the signal in M1 macrophages is activated stronger than in M2 macrophages [7]. By knocking out the key transcription factor RBP-J of the Notch signalling pathway from mice, the Notch signalling pathway is blocked and macrophages undergo irreversible transformation into M2 phenotype, thereby facilitating tumour proliferation, migration, invasion and immune escape.…”