Cotreatment with Smac mimetics and demethylating agents induces both apoptotic and necroptotic cell death pathways in
Steve Gerges1, Katharina Rohde1, Simone Fulda2
1Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstr. 3a, 60528 Frankfurt, Germany.
Abstract:
Treatment resistance in acute lymphoblastic leukemia (ALL) is often caused by defects in programmed cell death, e.g. by overexpression of Inhibitor of Apoptosis (IAP) proteins. Here, we report that small-molecule Smac mimetics (i.e. BV6, LCL161, birinapant) that neutralize x-linked IAP (XIAP), cellular IAP (cIAP)1 and cIAP2 cooperate with demethylating agents (i.e. 5-azacytidine (5AC) or 5-aza-2'-deoxycytidine (DAC)) to induce cell death in ALL cells. Molecular studies reveal that induction of cell death is preceded by BV6-mediated depletion of cIAP1 protein and involves tumor necrosis factor (TNF)α autocrine/paracrine signaling, since the TNFα-blocking antibody Enbrel significantly reduces BV6/5AC-induced cell death. While BV6/5AC cotreatment induces caspase-3 activation, the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD.fmk) only partly rescues ALL cells from BV6/5AC-induced cell death. This indicates that BV6/5AC cotreatment engages non-apoptotic cell death upon caspase inhibition. Indeed, genetic silencing of key components of necroptosis such as Receptor-Interacting Protein (RIP)3 or mixed lineage kinase domain-like (MLKL) in parallel with administration of zVAD.fmk provides a significantly better protection against BV6/5AC-induced cell death compared to the use of zVAD.fmk alone. Similarly, concomitant administration of pharmacological inhibitors of necroptosis (i.e. necrostatin-1s, GSK'872, dabrafenib, NSA) together with zVAD.fmk is superior in rescuing cells from BV6/5AC-induced cell death compared to the use of zVAD.fmk alone. These findings demonstrate that in ALL cells BV6/5AC-induced cell death is mediated via both apoptotic and necroptotic pathways. Importantly, BV6/5AC cotreatment triggers necroptosis in ALL cells that are resistant to apoptosis due to caspase inhibition. This opens new perspectives to overcome apoptosis resistance with important implications for the development of new treatment strategies for ALL.
Insights
Small-molecule Smac mimetics combined with demethylating agents induce cell death in acute lymphoblastic leukemia (ALL) by activating both apoptosis and necroptosis pathways. This combination therapy offers a promising strategy to overcome treatment resistance in ALL.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Treatment resistance in acute lymphoblastic leukemia (ALL) is frequently linked to impaired programmed cell death, often due to Inhibitor of Apoptosis (IAP) protein overexpression.
- Targeting IAP proteins offers a potential strategy to sensitize ALL cells to therapeutic interventions.
Purpose of the Study:
- To investigate the synergistic effects of small-molecule Smac mimetics and demethylating agents in inducing cell death in ALL cells.
- To elucidate the molecular mechanisms underlying the cell death pathways activated by this combination therapy.
Main Methods:
- Treatment of ALL cells with Smac mimetics (BV6, LCL161, birinapant) in combination with demethylating agents (5-azacytidine (5AC), 5-aza-2'-deoxycytidine (DAC)).
- Assessment of cell death induction, protein depletion (cIAP1), tumor necrosis factor (TNF)α signaling, and caspase activation.
- Evaluation of the roles of apoptosis and necroptosis pathways using caspase inhibitors (zVAD.fmk) and genetic/pharmacological inhibition of necroptosis components (RIP3, MLKL).
Main Results:
- BV6/5AC cotreatment effectively induced cell death in ALL cells, preceded by cIAP1 depletion and dependent on TNFα signaling.
- While BV6/5AC induced caspase activation, complete cell death rescue by caspase inhibition indicated engagement of non-apoptotic pathways.
- Inhibition of necroptosis components (RIP3, MLKL) or use of necroptosis inhibitors significantly enhanced protection against BV6/5AC-induced cell death when combined with caspase inhibition, confirming dual apoptotic and necroptotic cell death induction.
Conclusions:
- The combination of Smac mimetics and demethylating agents triggers both apoptotic and necroptotic cell death pathways in ALL cells.
- This cotreatment effectively induces necroptosis in apoptosis-resistant ALL cells, presenting a novel strategy to overcome therapeutic resistance.
- These findings hold significant implications for developing innovative treatment strategies for acute lymphoblastic leukemia.
Related Concept Videos
01:31The Intrinsic Apoptotic Pathway
02:50Combination Therapies and Personalized Medicine
The combination of the drug acetazolamide and sulforaphane is a good example of combination therapy to treat cancer. The cells in the interior of a large tumor often die due to the hypoxic and...
01:17The Extrinsic Apoptotic Pathway
02:57Targeted Cancer Therapies
There are several types of targeted therapies against...