title: p16INK4A sensitizes human leukemia cells to FAS- and glucocorticoid-induced apoptosis via induction of BBC3/Puma and repression of MCL1 and BCL2.
abstract: Loss of CDKN2A/p16(INK4A) in hematopoietic stem cells is associated with enhanced self-renewal capacity and might facilitate progression of damaged stem cells into pre-cancerous cells that give rise to leukemia. This is also reflected by the frequent loss of the INK4A locus in acute lymphoblastic T-cell leukemia. T-cell acute lymphoblastic leukemia cells designed to conditionally express p16(INK4A) arrest in the G(0)/G(1) phase of the cell cycle and show increased sensitivity to glucocorticoid- and tumor necrosis factor receptor superfamily 6-induced apoptosis. To investigate the underlying molecular mechanism for increased death sensitivity, we interfered with specific steps of apoptosis signaling by expression of anti-apoptotic proteins. We found that alterations in cell death susceptibility resulted from changes in the composition of pro- and anti-apoptotic BCL2 proteins, i.e. repression of MCL1, BCL2, and PMAIP1/Noxa and the induction of pro-apoptotic BBC3/Puma. Interference with Puma induction by short hairpin RNA technology or retroviral expression of MCL1 or BCL2 significantly reduced both glucocorticoid- and FAS-induced cell death in p16(INK4A)-reconstituted leukemia cells. These results suggest that Puma, in concert with MCL1 and BCL2 repression, critically mediates p16(INK4A)-induced death sensitization and that in human T-cell leukemia the deletion of p16(INK4A) confers apoptosis resistance by shifting the balance of pro- and anti-apoptotic BCL2 proteins toward apoptosis protection.
authors.affiliation: Tyrolean Cancer Research Institute, Department of Pediatrics IV, Medical University Innsbruck, Innsbruck 6020, Austria.
authors.forename: Petra
authors.initials: P
authors.lastname: Obexer
authors.forename: Judith
authors.initials: J
authors.lastname: Hagenbuchner
authors.forename: Martina
authors.initials: M
authors.lastname: Rupp
authors.forename: Christina
authors.initials: C
authors.lastname: Salvador
authors.forename: Markus
authors.initials: M
authors.lastname: Holzner
authors.forename: Martin
authors.initials: M
authors.lastname: Deutsch
authors.forename: Verena
authors.initials: V
authors.lastname: Porto
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kofler
authors.forename: Thomas
authors.initials: T
authors.lastname: Unterkircher
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Ausserlechner
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D053222:Fas Ligand Protein / Q000378:metabolism*; D015973:Gene Expression Regulation, Leukemic; D005938:Glucocorticoids / Q000378:metabolism; D006801:Humans; D007938:Leukemia / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D019941:Cyclin-Dependent Kinase Inhibitor p16; D053222:Fas Ligand Protein; D005938:Glucocorticoids; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2