Histone deacetylase inhibition by valproic acid down-regulates c-FLIP/CASH and sensitizes hepatoma cells towards CD95- and TRAIL receptor-mediated apoptosis and chemotherapy

Schuchmann, Marcus; Schulze‐Bergkamen, Henning; Fleischer, B.; Schattenberg, J. M.; Siebler, Jürgen; Weinmann, Arndt; Teufel, Andreas; Wörns, Marcus A.; Fischer, Thomas; Strand, Siri H.; Lohse, AW; Galle, Peter R.

doi:10.3892/or.15.1.227

Cited by 53 publications

(63 citation statements)

References 26 publications

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“…Although a number of studies have shown that HDAC inhibitor-mediated downregulation of FLIP sensitises various cancer cell lines to death ligands, such as TRAIL, 23,27,28 to our knowledge, no previous studies have directly examined whether FLIP downregulation is a sufficient death signal for apoptosis induction when these agents are administered as single agents. We found that FLIP downregulation in response to HDAC inhibitors results in caspase 8-and DR5-mediated apoptosis, phenocopying the mechanism of apoptosis that we previously observed in CRC cells following siRNA-mediated downregulation of FLIP.…”

Section: Discussionmentioning

confidence: 99%

Identification of an acetylation-dependant Ku70/FLIP complex that regulates FLIP expression and HDAC inhibitor-induced apoptosis

et al. 2012

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FLIP is a potential anti-cancer therapeutic target that inhibits apoptosis by blocking caspase 8 activation by death receptors. We report a novel interaction between FLIP and the DNA repair protein Ku70 that regulates FLIP protein stability by inhibiting its polyubiquitination. Furthermore, we found that the histone deacetylase (HDAC) inhibitor Vorinostat (SAHA) enhances the acetylation of Ku70, thereby disrupting the FLIP/Ku70 complex and triggering FLIP polyubiquitination and degradation by the proteasome. Using in vitro and in vivo colorectal cancer models, we further demonstrated that SAHA-induced apoptosis is dependant on FLIP downregulation and caspase 8 activation. In addition, an HDAC6-specific inhibitor Tubacin recapitulated the effects of SAHA, suggesting that HDAC6 is a key regulator of Ku70 acetylation and FLIP protein stability. Thus, HDAC inhibitors with anti-HDAC6 activity act as efficient post-transcriptional suppressors of FLIP expression and may, therefore, effectively act as 'FLIP inhibitors'. Cell Death and Differentiation (2012) 19, 1317-1327 doi:10.1038/cdd.2012 published online 10 February 2012 FLIP is an anti-apoptotic protein that blocks the activation of apoptosis mediated by death receptors, such as Fas, TRAIL receptor 1 (TRAIL-R1/DR4) and TRAIL-R2 (DR5).1 By binding to the adaptor protein FADD, FLIP inhibits apoptosis by blocking the processing and activation of procaspase 8 (FLICE) by death receptor complexes termed DISCs (death-inducing signalling complexes). 2 We previously reported that FLIP inhibits apoptosis induced by chemotherapeutic agents 3 and that high FLIP expression is an independent adverse prognostic biomarker in colorectal cancer (CRC). 4 These and other studies have indicated that inhibition of FLIP constitutes a promising therapeutic strategy for the treatment of CRC. Ku70 and its binding partner Ku80 are critical components of the non-homologous end joining (NHEJ) DNA repair machinery.5 Ku70 is regulated by acetylation, which is mediated by the histone acetyl transferases (HATs); CREBbinding protein (CBP) and PCAF, and its acetylation can be enhanced by treating cells with histone deacetylase (HDAC) inhibitors.6 Ku70 acetylation disrupts its DNA-binding activity and sensitises cells to DNA-damaging agents. 7 In addition, cytoplasmic Ku70 binds to and regulates the pro-apoptotic Bcl-2 family member, Bax.6 Ku70 simultaneously inhibits Bax degradation via the ubiquitin proteasome system (UPS) and prevents its translocation to the mitochondria. 8 Moreover, it has been reported that Ku70 may have intrinsic deubiquitinating (DUB) activity.8 The Ku70-Bax complex is disrupted by Ku70 acetylation, which promotes Bax translocation to mitochondria and apoptosis induction. Herein, we report a novel interaction between FLIP and Ku70 that regulates FLIP stability. This interaction is acetylation-dependant and is disrupted by HDAC inhibitors with activity against HDAC6. Disruption of the Ku70-FLIP interaction subsequently leads to FLIP degradation by the UPS and induction of c...

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Section: Discussionmentioning

confidence: 99%

Identification of an acetylation-dependant Ku70/FLIP complex that regulates FLIP expression and HDAC inhibitor-induced apoptosis

et al. 2012

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“…We and others have reported that chemical and genetic inhibition of HDACs leads to decreased expression of FLIP mRNA (36)(37)(38)(39)(40)(41)(42)(43). However, the mechanism by which inhibiting HDACs decreases FLIP expression is uncertain.…”

Section: Discussionmentioning

confidence: 99%

Selective Inhibition of Histone Deacetylases Sensitizes Malignant Cells to Death Receptor Ligands

Wood

Dalili

Simpson

et al. 2010

Molecular Cancer Therapeutics

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Evasion of death receptor ligand-induced apoptosis represents an important contributor to cancer development and progression. Therefore, molecules that restore sensitivity to death receptor stimuli would be important tools to better understand this biological pathway and potential leads for therapeutic adjuncts. Previously, the small-molecule 4-(4-chloro-2-methylphenoxy)-N-hydroxybutanamide (that we propose be named droxinostat) was identified as a chemical sensitizer to death receptor stimuli, decreasing the expression of the caspase-8 inhibitor FLIP. However, the direct targets of droxinostat were unknown. To better understand the mechanism of action of droxinostat and highlight new strategies to restore sensitivity to death receptor ligands, we analyzed changes in gene expression using the Connectivity Map after treating cells with droxinostat. Changes in gene expression after droxinostat treatment resembled changes observed after treatment with histone deacetylase (HDAC) inhibitors. Therefore, we examined the effects of droxinostat on HDAC activity and showed that it selectively inhibited HDAC3, HDAC6, and HDAC8 and that inhibition of these HDACs was functionally important for its ability to sensitize cells to death ligands. Thus, we have identified a selective HDAC inhibitor and showed that selective HDAC inhibition sensitizes cells to death ligands, thereby highlighting a new mechanism to overcome resistance to death receptor ligands. Mol Cancer Ther; 9(1); 246-56. ©2010 AACR.

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“…Indeed, a variety of class I and II HDAC inhibitors, for example valproic acid, depsipeptide, sodium butyrate, trichostatin A and LAQ824, have been shown to decrease expression levels of c-FLIP [1,10,20,24,33]. However, inhibitor of SIRT1 deacetylase, a member of the class III HDAC family, has not been reported to augment TRAIL-induced apoptosis and its mechanism.…”

Section: Introductionmentioning

confidence: 99%

Inhibition of SIRT1 Sensitizes TRAIL-Resistant MCF-7 Cells by Upregulation of DR5 and Inhibition of c-FLIP

Lee¹,

Kim²,

Kim³

et al. 2012

Journal of Life Science

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The tumor necrosis, factor-related, apoptosis-inducing ligand (TRAIL) is regarded as a potentially useful anticancer agent with excellent selectivity for cancer cells. However, a considerable number of cancer cells are resistant to apoptosis induction by TRAIL. Developing strategies to overcome this resistance are important for the successful use of TRAIL for cancer therapy. Here, we revealed that siRNA-mediated downregulation of SIRT1 or SIRT1 inhibitor Amurensin G upregulated DR5 and c-Myc and downregulated c-FLIPL/S and Mcl-1, which was associated with sensitization of TRAIL-resistant MCF-7 cells to TRAIL. This result was followed by the activation of caspases, PARP cleavage, and downregulation of Bcl-2 in both TRAIL-treated MCF-7 cells transfected with SIRT1 siRNA and cells co-treated with Amurensin G and TRAIL. Our results suggest that the induction of DR5 and downregulation of c-FLIP via suppression of SIRT1 expression may be a useful strategy to increase the susceptibility of TRAIL-resistant cancer cells to TRAIL-induced cell death.

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Histone deacetylase inhibition by valproic acid down-regulates c-FLIP/CASH and sensitizes hepatoma cells towards CD95- and TRAIL receptor-mediated apoptosis and chemotherapy

Cited by 53 publications

References 26 publications

Identification of an acetylation-dependant Ku70/FLIP complex that regulates FLIP expression and HDAC inhibitor-induced apoptosis

Identification of an acetylation-dependant Ku70/FLIP complex that regulates FLIP expression and HDAC inhibitor-induced apoptosis

Selective Inhibition of Histone Deacetylases Sensitizes Malignant Cells to Death Receptor Ligands

Inhibition of SIRT1 Sensitizes TRAIL-Resistant MCF-7 Cells by Upregulation of DR5 and Inhibition of c-FLIP

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