Global metabolic profile identifies choline kinase alpha as a key regulator of glutathione-dependent antioxidant cell defense in ovarian carcinoma

// Anna Granata 1 , Roberta Nicoletti 1 , Paola Perego 2 , Egidio Iorio 3 , Balaji Krishnamachary 4 , Fabio Benigni 5 , Alessandro Ricci 3 , Franca Podo 3 , Zaver M. Bhujwalla 4 , Silvana Canevari 1 , Marina Bagnoli 1,* and Delia Mezzanzanica 1,* 1 Unit of Molecular Therapies, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy 2 Molecular Pharmacology, Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy 3 Department of Cell Biology and Neurosciences, Istituto Superiore di Sanita, Rome, Italy 4 Division of Cancer Imaging Research, In Vivo Cellular and Molecular Imaging Center, Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, USA 5 Division of Oncology, Urological Research Institute, IRCCS Ospedale San Raffaele, Milan, Italy * These authors are equally contributed to this work Correspondence to: Delia Mezzanzanica, email: // Marina Bagnoli, email: // Keywords : Choline kinase, ovarian cancer, phosphocholine metabolism, glutathione, reversal of drug resistance Received : January 07, 2015 Accepted : February 19, 2015 Published : March 14, 2015 Abstract Epithelial Ovarian Cancer (EOC) “ cholinic phenotype”, characterized by increased intracellular phosphocholine content sustained by over-expression/activity of choline kinase-alpha (ChoKα/CHKA), is a metabolic cellular reprogramming involved in chemoresistance with still unknown mechanisms. By stable CHKA silencing and global metabolic profiling here we demonstrate that CHKA knockdown hampers growth capability of EOC cell lines both in vitro and in xenotransplant in vivo models. It also affected antioxidant cellular defenses, decreasing glutathione and cysteine content while increasing intracellular levels of reactive oxygen species, overall sensitizing EOC cells to current chemotherapeutic regimens. Natural recovering of ChoKα expression after its transient silencing rescued the wild-type phenotype, restoring intracellular glutathione content and drug resistance. Rescue and phenocopy of siCHKA-related effects were also obtained by artificial modulation of glutathione levels. The direct relationship among CHKA expression, glutathione intracellular content and drug sensitivity was overall demonstrated in six different EOC cell lines but notably, siCHKA did not affect growth capability, glutathione metabolism and/or drug sensitivity of non-tumoral immortalized ovarian cells. The “ cholinic phenotype”, by recapitulating EOC addiction to glutathione content for the maintenance of the antioxidant defense, can be therefore considered a unique feature of cancer cells and a suitable target to improve chemotherapeutics efficacy.