LGR5 regulates pro-survival MEK/ERK and proliferative Wnt/β-catenin signalling in neuroblastoma.
LGR5 is a marker of normal and cancer stem cells in various tissues where it functions as a receptor for R-spondins and increases canonical Wnt signalling amplitude. Here we report that LGR5 is also highly expressed in a subset of high grade neuroblastomas. Neuroblastoma is a clinically heterogenous paediatric cancer comprising a high proportion of poor prognosis cases (~40%) which are frequently lethal. Unlike many cancers, Wnt pathway mutations are not apparent in neuroblastoma, although previous microarray analyses have implicated deregulated Wnt signalling in high-risk neuroblastoma. We demonstrate that LGR5 facilitates high Wnt signalling in neuroblastoma cell lines treated with Wnt3a and R-spondins, with SK-N-BE(2)-C, SK-N-NAS and SH-SY5Y cell-lines all displaying strong Wnt induction. These lines represent MYCN-amplified, NRAS and ALK mutant neuroblastoma subtypes respectively. Wnt3a/R-Spondin treatment also promoted nuclear translocation of β-catenin, increased proliferation and activation of Wnt target genes. Strikingly, short-interfering RNA mediated knockdown of LGR5 induces dramatic Wnt-independent apoptosis in all three cell-lines, accompanied by greatly diminished phosphorylation of mitogen/extracellular signal-regulated kinases (MEK1/2) and extracellular signal-regulated kinases (ERK1/2), and an increase of BimEL, an apoptosis facilitator downstream of ERK. Akt signalling is also decreased by a Rictor dependent, PDK1-independent mechanism. LGR5 expression is cell cycle regulated and LGR5 depletion triggers G1 cell-cycle arrest, increased p27 and decreased phosphorylated retinoblastoma protein. Our study therefore characterises new cancer-associated pathways regulated by LGR5, and suggest that targeting of LGR5 may be of therapeutic benefit for neuroblastomas with diverse etiologies, as well as other cancers expressing high LGR5.
['Vieira|Gabriella Cunha|GC|', 'Chockalingam|S|S|', 'Melegh|Zsombor|Z|', 'Greenhough|Alexander|A|', 'Malik|Sally|S|', 'Szemes|Marianna|M|', 'Park|Ji Hyun|JH|', 'Kaidi|Abderrahmane|A|', 'Zhou|Li|L|', 'Catchpoole|Daniel|D|', 'Morgan|Rhys|R|', 'Bates|David O|DO|', 'Gabb|Peter David|PD|', 'Malik|Karim|K|']
D017209:Apoptosis D045744:Cell Line, Tumor D049109:Cell Proliferation D002470:Cell Survival D002648:Child D002675:Child, Preschool D048049:Extracellular Signal-Regulated MAP Kinases D015972:Gene Expression Regulation, Neoplastic D006801:Humans D015151:Immunoblotting D007223:Infant D007231:Infant, Newborn D018613:Microscopy, Confocal D020929:Mitogen-Activated Protein Kinase Kinases D009447:Neuroblastoma D034622:RNA Interference D043562:Receptors, G-Protein-Coupled D020133:Reverse Transcriptase Polymerase Chain Reaction D060449:Wnt Signaling Pathway D051176:beta Catenin
LGR5 MEK/ERK Wnt/β-catenin neuroblastoma cell survival