title: Transforming growth factor-β directly induces p53-up-regulated modulator of apoptosis (PUMA) during the rapid induction of apoptosis in myc-driven B-cell lymphomas.
abstract: c-Myc transformed human Burkitt's lymphoma (BL) cells are highly sensitive to TGF-β-induced apoptosis. Previously we demonstrated that TGF-β-mediated cell death in BL cells is regulated via the mitochondrial intrinsic apoptosis pathway, which is dependent on the activation of BAX and/or BAK. TGF-β directly induces transcription of the BH3-only protein BIK and represses expression of the pro-survival factor BCL-X(L) but has no effect on the direct BAX/BAK "activators" BIM or BID (tBID). Here we show that TGF-β induces the BH3-only activator PUMA to aid induction of the intrinsic cell death pathway. TGF-β also induced PUMA in normal germinal center CD77-positive centroblasts isolated from human tonsil tissue. PUMA was a direct TGF-β target gene in B-cells, and we identify a putative Smad-binding region within the human PUMA promoter that recruits Smad3 and Smad4 in cells in response to TGF-β signaling. Constitutive activity of the isolated Smad-binding region in luciferase reporter assays was dependent on Smad consensus sequences and was partially dependent on endogenous TGF-β signaling and Smad4. Knockdown of PUMA in BL cells using lentiviral shRNA resulted in slower kinetics of the TGF-β-mediated apoptotic response. Analysis of Eμ-Myc cell lines demonstrated that c-myc-driven murine lymphomas are also sensitive to TGF-β-mediated apoptosis. Moreover, Puma(-/-) Eμ-Myc lines demonstrated significantly delayed kinetics of the apoptotic response when compared with wild type lymphomas. TGF-β therefore induces a polygenic response in Myc-driven lymphomas involving transcription of PUMA, which is necessary for the rapid induction of cell death.
authors.affiliation: Division of Cancer Research, Medical Research Institute, Jacqui Wood Cancer Centre, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, United Kingdom.
authors.forename: Lindsay C
authors.initials: LC
authors.lastname: Spender
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Carter
authors.forename: Darren I
authors.initials: DI
authors.lastname: O'Brien
authors.forename: Louise J
authors.initials: LJ
authors.lastname: Clark
authors.forename: Jian
authors.initials: J
authors.lastname: Yu
authors.forename: Ewa M
authors.initials: EM
authors.lastname: Michalak
authors.forename: Lina
authors.initials: L
authors.lastname: Happo
authors.forename: Mark S
authors.initials: MS
authors.lastname: Cragg
authors.forename: Gareth J
authors.initials: GJ
authors.lastname: Inman
mesh_terms: D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D007700:Kinetics; D008223:Lymphoma / Q000378:metabolism; D016393:Lymphoma, B-Cell / Q000378:metabolism*; D051379:Mice; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D015398:Signal Transduction; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc; C495901:TP53 protein, human; D016212:Transforming Growth Factor beta; D016159:Tumor Suppressor Protein p53