Identification of a novel synergistic induction of cell death by Smac mimetic and HDAC inhibitors in acute myeloid leukemia cells. Issue 1 (28th September 2015)

• Record Type: Journal Article
• Authors: Steinwascher, Sofie; Nugues, Anne-Lucie; Schoeneberger, Hannah; Fulda, Simone
• Is Part Of: Cancer letters. Volume 366:Issue 1(2015)
• Page Start: 32
• Page End: 43
• Publication Date: 2015-09-28
• Subjects: Apoptosis -- Smac -- Leukemia -- Necroptosis; AML acute myeloid leukemia -- CI combination index -- cIAP cellular inhibitor of apoptosis protein -- FACS fluorescence-activated cell-sorting analysis -- FCS fetal calf serum -- FLT3 Fms-like tyrosine kinase 3 -- FSC/SSC forward/side scatter -- GAPDH glyceraldehyde 3-phosphate dehydrogenase -- HDAC histone deacetylase -- HDACIs HDAC inhibitors -- HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid -- IAP inhibitor of apoptosis protein -- MLKL mixed lineage kinase domain-like protein -- Nec-1 necrostatin-1 -- NF-κB nuclear factor kappaB -- NSA necrosulfonamide -- PI propidium iodide -- PBL peripheral blood lymphocyte -- RING Really Interesting New Gene -- RIP1 receptor-interacting protein 1 -- Smac second mitochondrial-derived activator of caspases -- TNF tumor necrosis factor -- TNFR1 tumor necrosis factor receptor 1 -- TRAIL TNF-related apoptosis-inducing ligand -- XIAP X-linked inhibitor of apoptosis -- zVAD.fmk N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone; Cancer -- Periodicals; Neoplasms -- Periodicals; Cancer -- Périodiques; Electronic journals; 616.994
• DOI: 10.1016/j.canlet.2015.05.020
• Languages: English
• ISSNs: 0304-3835

Abstract

Highlights: Synergistic interaction of Smac mimetic and HDAC inhibitors in AML cell lines. No synergistic toxicity by combination treatment against normal peripheral blood lymphocytes. Smac mimetic and HDAC inhibitors can trigger necroptosis when caspase activation is blocked. Abstract: Inhibitor of Apoptosis (IAP) proteins are expressed at high levels in acute myeloid leukemia (AML) and contribute to resistance to programmed cell death. Here, we report that inhibition of IAP proteins by the small-molecule Smac mimetic BV6 acts together with histone deacetylase (HDAC) inhibitors (HDACIs) such as MS275 or SAHA to trigger cell death in AML cell lines in a synergistic manner, as underscored by calculation of combination index (CI). Also, BV6 and HDACIs cooperate to trigger DNA fragmentation, a marker of apoptotic cell death, and to suppress long-term clonogenic survival of AML cells. In contrast, equimolar concentrations of BV6 and MS275 or SAHA do not synergize to elicit cell death in normal peripheral blood lymphocytes (PBLs), emphasizing some tumor cell selectivity of this combination treatment. Addition of the tumor necrosis factor (TNF)α-blocking antibody Enbrel significantly reduces BV6/MS275-induced cell death in the majority of AML cell lines, indicating that autocrine/paracrine TNFα signaling contributes to cell death. Remarkably, the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) fails to rescue MV4-11, Molm13 and OCI-AML3 cells and even enhances BV6/MS275-mediated cell death, whereas zVAD.fmk reduces BV6/MS275-induced cell death in NB4 cells. Annexin-V/propidium iodide (PI) double staining reveals that BV6/MS275 cotreatment predominately increases the percentage of double-positive cells. Of note, the Receptor-Interacting Protein (RIP)1 inhibitor necrostatin-1 (Nec-1) or the Mixed Lineage Kinase Domain-Like protein (MLKL) inhibitor necrosulfonamide (NSA) significantly reduce BV6/MS275-induced cell death in the presence of zVAD.fmk, suggesting that BV6/MS275 cotreatment triggers necroptosis when caspases are inhibited. Thus, BV6 acts in concert with HDACIs to induce cell death in AML cells and can bypass apoptosis resistance, at least in several AML cell lines, by engaging necroptosis as an alternative route of regulated cell death. The identification of a novel synergism of BV6 and HDACIs has important implications for the development of new treatment strategies for AML.