Targeting inhibitor of apoptosis proteins by Smac mimetic elicits cell death in poor prognostic subgroups of chronic lymphocytic leukemia

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Item Type:	Article
Title:	Targeting inhibitor of apoptosis proteins by Smac mimetic elicits cell death in poor prognostic subgroups of chronic lymphocytic leukemia
Creators Name:	Opel, D., Schnaiter, A., Dodier, D., Jovanovic, M., Gerhardinger, A., Idler, I., Mertens, D., Bullinger, L., Stilgenbauer, S. and Fulda, S.
Abstract:	Inhibitor of apoptosis (IAP) proteins are highly expressed in chronic lymphocytic leukemia (CLL) cells and contribute to evasion of cell death and poor therapeutic response. Here, we report that Smac mimetic BV6 dose-dependently induces cell death in 28 of 51 (54%) investigated CLL samples, while B-cells from healthy donors are largely unaffected. Importantly, BV6 is significantly more effective in prognostic unfavorable cases with, e.g., non-mutated VH status and TP53 mutation than samples with unknown or favorable prognosis. The majority of cases with 17p deletion (10/12) and Fludarabine refractory cases respond to BV6, indicating that BV6 acts independently of p53. BV6 also triggers cell death under survival conditions mimicking the microenvironment, e.g., by adding CD40 ligand or conditioned medium. Gene expression profiling identifies cell death, NF-κB and redox signaling among the top pathways regulated by BV6 not only in CLL but also in core-binding factor (CBF) acute myeloid leukemia (AML). Consistently, BV6 stimulates production of reactive oxygen species (ROS), which are contributing to BV6-induced cell death, since antioxidants reduce cell death. While BV6 causes degradation of cellular inhibitor of apoptosis (cIAP)1 and cIAP2 and nuclear factor-kappaB (NF-κB) pathway activation in primary CLL samples, BV6 induces cell death independently of caspase activity, receptor-interacting protein (RIP)1 activity or tumor necrosis factor (TNF)α, as zVAD.fmk, necrostatin-1 or TNFα-blocking antibody Enbrel fail to inhibit cell death. Together, these novel insights into BV6-regulated cell death in CLL have important implications for developing new therapeutic strategies to overcome cell death resistance especially in poor prognostic CLL subgroups.
Keywords:	IAP Proteins, Smac Mimetic, CLL, Cell Death
Source:	International Journal of Cancer
ISSN:	0020-7136
Publisher:	Wiley
Volume:	137
Number:	12
Page Range:	2959-2970
Date:	15 December 2015
Official Publication:	https://doi.org/10.1002/ijc.29650
PubMed:	View item in PubMed

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