WNK1 kinase and its partners Akt, SGK1 and NBC-family Na + /HCO3 – cotransporters are potential therapeutic targets for glioblastoma stem-like cells linked to Bisacodyl signaling

// Wanyin Chen 1 , Leonel Nguekeu Zebaze 1 , Jihu Dong 1 , Laetitia Chezeau 1 , Perrine Inquimbert 2 , Sylvain Hugel 2 , Songlin Niu 1 , Frederic Bihel 1 , Emmanuel Boutant 3 , Eleonore Real 3 , Pascal Villa 4 , Marie-Pierre Junier 5 , Herve Chneiweiss 5 , Marcel Hibert 1 , Jacques Haiech 1 , Marie-Claude Kilhoffer 1 and Maria Zeniou 1 1 Laboratoire d’Innovation Therapeutique, Centre National de la Recherche Scientifique/Universite de Strasbourg, UMR7200, Laboratoire d’Excellence Medalis, Faculte de Pharmacie, Illkirch 67401, France 2 Institut des Neurosciences Cellulaires et Integratives, UPR3212, Centre National de la Recherche Scientifique, 67084 Strasbourg, France; Universite de Strasbourg, Strasbourg 67084, France 3 Laboratoire de Bioimagerie et Pathologies - LBP, UMR7021, Centre National de la Recherche Scientifique/Universite de Strasbourg, Faculte de Pharmacie, Illkirch 67401, France 4 Plateforme de Chimie Biologie Integrative (PCBIS), Universite de Strasbourg/CNRS UMS 3286, Laboratoire d’Excellence Medalis, ESBS Pole API-Bld Sebastien Brant, Illkirch 67401, France 5 Neuroscience Paris Seine-IBPS, CNRS UMR 8246/Inserm U1130/UPMC UMCR18, Paris 75005, France Correspondence to: Maria Zeniou, email: zeniou@unistra.fr Keywords: Bisacodyl/DDPM; glioblastoma cancer stem-like cells; WNK1; Akt/SGK1; NBC Na + /HCO3 − cotransporters Received: December 06, 2017      Accepted: May 10, 2018      Published: June 05, 2018 ABSTRACT Glioblastoma is a highly heterogeneous brain tumor. The presence of cancer cells with stem-like and tumor initiation/propagation properties contributes to poor prognosis. Glioblastoma cancer stem-like cells (GSC) reside in hypoxic and acidic niches favoring cell quiescence and drug resistance. A high throughput screening recently identified the laxative Bisacodyl as a cytotoxic compound targeting quiescent GSC placed in acidic microenvironments. Bisacodyl activity requires its hydrolysis into DDPM, its pharmacologically active derivative. Bisacodyl was further shown to induce tumor shrinking and increase survival in in vivo glioblastoma models. Here we explored the cellular mechanism underlying Bisacodyl cytotoxic effects using quiescent GSC in an acidic microenvironment and GSC-derived 3D macro-spheres. These spheres mimic many aspects of glioblastoma tumors in vivo , including hypoxic/acidic areas containing quiescent cells. Phosphokinase protein arrays combined with pharmacological and genetic modulation of signaling pathways point to the WNK1 serine/threonine protein kinase as a mediator of Bisacodyl cytotoxic effect in both cell models. WNK1 partners including the Akt and SGK1 protein kinases and NBC-family Na + /HCO3 − cotransporters were shown to participate in the compound’s effect on GSC. Overall, our findings uncover novel potential therapeutic targets for combatting glioblastoma which is presently an incurable disease.