title: Therapeutic targeting of necroptosis by Smac mimetic bypasses apoptosis resistance in acute myeloid leukemia cells.
abstract: Resistance to apoptosis, for example due to overexpression of Inhibitor of Apoptosis (IAP) proteins, is associated with poor prognosis in acute myeloid leukemia (AML). Here, we identify that Smac mimetics such as BV6, which antagonizes IAP proteins, elicit necroptosis in AML cells, in which apoptosis is inhibited pharmacologically by caspase inhibitors or genetically by caspase-8 knockdown. Importantly, BV6 triggers necroptosis also in apoptosis-resistant patient-derived AML blasts, underlining the clinical relevance of our findings. Mechanistically, we show that BV6-induced cell death depends on key components of necroptosis signaling such as RIP1, RIP3 and MLKL, since pharmacological or genetic inhibition of these proteins significantly protects AML cells from BV6-mediated cell death, whereas PGAM5 is dispensable. Interestingly, we identify constitutive tumor necrosis factor-alpha (TNFα) secretion and an autocrine/paracrine TNFα loop as critical mediators of BV6-induced necroptosis in AML cell lines and patient-derived blasts, as the TNFα-blocking antibody Enbrel or tumor necrosis factor-alpha receptor 1 (TNFR1) knockdown significantly rescue cell death. Notably, AML cells exhibit high basal levels of TNFα compared to non-malignant CD34+ cells, which is further increased by BV6. In conclusion, this is the first report showing that Smac mimetics circumvent apoptosis resistance in AML cells by inducing necroptosis in a TNFα-dependent manner, which has important implications for the development of new strategies to overcome treatment resistance in AML.
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Safferthal
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Rohde
authors.affiliation: Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Germany.|German Cancer Consortium (DKTK), Heidelberg, Germany.|German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Fulda
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000737:chemistry / Q000378:metabolism; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D009336:Necrosis; D009842:Oligopeptides / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: C582180:BV6 peptide; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D009842:Oligopeptides; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; C570693:MLKL protein, human; D011494:Protein Kinases; C529563:PGAM5 protein, human; D010749:Phosphoprotein Phosphatases; D020169:Caspases; D020558:GTP Phosphohydrolases; C110768:DNM1L protein, human; D034281:Dynamins