title: Sphingosine analogue drug FTY720 targets I2PP2A/SET and mediates lung tumour suppression via activation of PP2A-RIPK1-dependent necroptosis.
abstract: Mechanisms that alter protein phosphatase 2A (PP2A)-dependent lung tumour suppression via the I2PP2A/SET oncoprotein are unknown. We show here that the tumour suppressor ceramide binds I2PP2A/SET selectively in the nucleus and including its K209 and Y122 residues as determined by molecular modelling/simulations and site-directed mutagenesis. Because I2PP2A/SET was found overexpressed, whereas ceramide was downregulated in lung tumours, a sphingolipid analogue drug, FTY720, was identified to mimick ceramide for binding and targeting I2PP2A/SET, leading to PP2A reactivation, lung cancer cell death, and tumour suppression in vivo. Accordingly, while molecular targeting of I2PP2A/SET by stable knockdown prevented further tumour suppression by FTY720, reconstitution of WT-I2PP2A/SET expression restored this process. Mechanistically, targeting I2PP2A/SET by FTY720 mediated PP2A/RIPK1-dependent programmed necrosis (necroptosis), but not by apoptosis. The RIPK1 inhibitor necrostatin and knockdown or genetic loss of RIPK1 prevented growth inhibition by FTY720. Expression of WT- or death-domain-deleted (DDD)-RIPK1, but not the kinase-domain-deleted (KDD)-RIPK1, restored FTY720-mediated necroptosis in RIPK1(-/-)  MEFs. Thus, these data suggest that targeting I2PP2A/SET by FTY720 suppresses lung tumour growth, at least in part, via PP2A activation and necroptosis mediated by the kinase domain of RIPK1.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Sahar A
authors.initials: SA
authors.lastname: Saddoughi
authors.forename: Salih
authors.initials: S
authors.lastname: Gencer
authors.forename: Yuri K
authors.initials: YK
authors.lastname: Peterson
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Ward
authors.forename: Archana
authors.initials: A
authors.lastname: Mukhopadhyay
authors.forename: Joshua
authors.initials: J
authors.lastname: Oaks
authors.forename: Jacek
authors.initials: J
authors.lastname: Bielawski
authors.forename: Zdzislaw M
authors.initials: ZM
authors.lastname: Szulc
authors.forename: Raquela J
authors.initials: RJ
authors.lastname: Thomas
authors.forename: Shanmugam P
authors.initials: SP
authors.lastname: Selvam
authors.forename: Can E
authors.initials: CE
authors.lastname: Senkal
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Garrett-Mayer
authors.forename: Ryan M
authors.initials: RM
authors.lastname: De Palma
authors.forename: Dzmitry
authors.initials: D
authors.lastname: Fedarovich
authors.forename: Angen
authors.initials: A
authors.lastname: Liu
authors.forename: Amyn A
authors.initials: AA
authors.lastname: Habib
authors.forename: Robert V
authors.initials: RV
authors.lastname: Stahelin
authors.forename: Danilo
authors.initials: D
authors.lastname: Perrotti
authors.forename: Besim
authors.initials: B
authors.lastname: Ogretmen
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins; D000068876:Fingolimod Hydrochloride; D055785:Gene Knockdown Techniques; D056488:Histone Chaperones / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D008958:Models, Molecular; D009336:Necrosis; D010766:Phosphorylation; D011409:Propylene Glycols / Q000378:metabolism / Q000494:pharmacology*; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D053422:Receptor-Interacting Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D056488:Histone Chaperones; D011409:Propylene Glycols; C513473:SET protein, human; D014157:Transcription Factors; C506249:RIPK1 protein, human; D053422:Receptor-Interacting Protein Serine-Threonine Kinases; D054648:Protein Phosphatase 2; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine