TAMI-17. INDUCTION OF SYNTHETIC LETHALITY BY ACTIVATION OF MITOCHONDRIAL CLPP AND INHIBITION OF HDAC1/2 IN GLIOBLASTOMA

2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi201-vi201
Author(s):  
Trang Nguyen ◽  
Enyuan Shang ◽  
Salveena Schiffgens ◽  
Consuelo Torrini ◽  
Elena Bianchetti ◽  
...  

Abstract Activation of the mitochondrial ClpP protease is an innovative therapeutic concept and the identification of synthetic lethal interactions may foster the development of novel therapies for glioblastoma (GBM). By integration of a transcriptome, metabolite and U-13C-glucose tracing analyses, we showed that activation of the mitochondrial ClpP protease through constitutively active ClpP (Y118A) or utilization of second-generation imipridone compounds (ONC206 and ONC212) in combination with genetic interference of HDAC1 and HDAC2 as well as with global (Panobinostat) and selective (Romidepsin) HDAC inhibitors caused synergistic reduction of viability in established, neuro-sphere and patient-derived xenograft (PDX) cultures of human GBM, which was mediated by interference with tricarboxylic acid cycle activity and GBM cell respiration. Notably, human astrocytes were significantly less susceptible to the combination treatment of HDAC-inhibitors and ClpP activators. The reduction of GBM viability occurred independent of TP53 status and was accompanied by activation of cell death with apoptotic features along with cleavage of caspases regulated chiefly by Bcl-xL and Mcl-1. Importantly, knockdown of the ClpP protease or ectopic expression of a ClpP D190A mutant almost completely rescued from the inhibition of oxidative energy metabolism as well as from the reduction of cellular viability by ClpP activators and the combination treatment, suggesting critical involvement of this protein. Finally, utilizing GBM PDX models, we demonstrated that the combination treatment of HDAC-inhibitors and imipridones reduced tumor growth and prolonged host survival more potently than single treatments or vehicle in vivo. Collectively, these observations suggest that the efficacy of HDAC inhibitors might be significantly enhanced through ClpP activators in model systems of human GBM.

2020 ◽  
Vol 22 (Supplement_2) ◽  
pp. ii98-ii98
Author(s):  
Salveena Schiffgens ◽  
Trang Nguyen ◽  
Chang Shu ◽  
Bianchetti Elena ◽  
Consuelo Torrini ◽  
...  

Abstract Novel therapeutic targets are critical to unravel for recalcitrant malignancies, such as the most common primary brain tumor in adults, glioblastoma (GBM). Heterogeneity remains a hallmark of primary glial brain tumors and therefore targeting several pathways simultaneously is an appropriate approach. Here, we showed that pharmacological activation of the mitochondrial ClpP protease through utilization of the novel imipridone compounds (ONC206 and ONC212) in combination with global (Panobinostat) and selective (romidepsin) HDAC – inhibitors caused synergistic reduction of viability in established and patient-derived xenograft (PDX) cultures of human GBM. This effect occurred independent of TP53 status and was partially mediated by activation of a cell death with apoptotic features accompanied by activation of initiator and effector caspases as well as cleavage of PARP. Consistently, the combination treatment altered the expression of anti-apoptotic and pro-apoptotic Bcl-2 family members, resulting in down-regulation of Bcl-xL and Mcl-1. Knockdown experiments targeting Noxa, BIM, Bcl-xL and Mcl-1 confirmed a functional implication of these proteins in the reduction of cellular viability mediated by the combination treatment. Importantly, knockdown of the ClpP protease significantly rescued the reduction of cellular viability by ClpP activators and the combination treatment, respectively, suggesting critical involvement of this protein. Finally, using a PDX model, we demonstrated that the combination treatment of romidepsin and ONC206 reduced tumor growth more potently than single treatments or vehicle by enhanced reduction of cellular proliferation and pronounced induction of cell death in vivo. Collectively, these observations suggest that the efficacy of HDAC-inhibitors might be significantly enhanced through ClpP activators in model systems of human GBM.


2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi215-vi216
Author(s):  
Melanie Schoof ◽  
Carolin Göbel ◽  
Dörthe Holdhof ◽  
Sina Al-Kershi ◽  
Ulrich Schüller

Abstract DNA methylation based classification of brain tumors has revealed a high heterogeneity between tumors and led to the description of multiple distinct subclasses. The increasing subdivision of tumors can help to understand molecular mechanisms of tumor development and to improve therapy if appropriate model systems for preclinical research are available. Multiple recent publications have described a subgroup of pediatric glioblastoma which is clearly separable from other pediatric and adult glioblastoma in its DNA methylation profile (GBM MYCN). Many cases in this group are driven by MYCN amplifications and harbor TP53 mutations. These tumors almost exclusively occur in children and were further described as highly aggressive with a median overall survival of only 14 months. In order to further investigate the biology and treatment options of these tumors, we generated hGFAP-cre::TP53 Fl/Fl ::lsl-MYCN mice. These mice carry a loss of TP53 and show aberrant MYCN expression in neural precursors of the central nervous system. The animals develop large forebrain tumors within the first 80 days of life with 100 % penetrance. These tumors resemble human GBM MYCN tumors histologically and are sensitive to AURKA and ATR inhibitors in vitro. We believe that further characterization of the model and in vivo treatment studies will pave the way to improve treatment of patients with these highly aggressive tumors.


Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3985-3985
Author(s):  
Yihong Guan ◽  
Anand D. Tiwari ◽  
Metis Hasipek ◽  
Dale Grabowski ◽  
Daniel Lindner ◽  
...  

Abstract Background: TET-dioxygenases (TET1, TET2, and TET3) are key epigenetic regulators, which require molecular oxygen, αKG, and Fe 2+ to progressively oxidize 5-methylcytosine to 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine, leading to the demethylation of mCpGs at promoter and enhancer, a key step for mounting an efficient transcription profile and thereby differentiation. Loss of function TET2 mutation (TET2 MT) is frequently observed in myeloid neoplasms (MN). Despite extensive studies of the biochemical mechanisms underlying distorted myeloid differentiation and neoplastic evolution of TET2 MT HSPCs, targeted therapies are lagging. Here, we report the therapeutic utility of preferential targeting of TET2 mutant and TET-dioxygenase deficient cells either by restoring the lost activity to induce differentiation and death or by inhibiting the residual activity to induce synthetic lethality. Methods: Genetic as well as pharmacologic in vitro and in vivo models of AML were used to validate specific targeting of TET2 mutant cells. Knockout and over-expression in the isogenic background of different cells were used to understand the pro-survival and proliferative mechanism of TET2 loss in myeloid cells. The efficacy of small molecule pharmacophore targeting TET-dioxygenase was evaluated in vitro in cell free and cell culture as well as in vivo in a mouse competitive transplant model to demonstrate the proof of therapeutic concept. Result: Ascorbate, used as an activator of αKG/Fe 2+ dependent dioxygenase including TETs, functions via maintaining the redox state of iron (II) in the dioxygenase catalytic site with a half-maximal effective concentration of 13.8 ± 1.3 µM for enhancing TET2activity as measured by an ELISA for 5hmC. However, the reported intracellular cellular concentrations of ascorbate in human remains in the millimolar range, well above the saturating concentration required for TET-dioxygenases activation. Interestingly, ascorbate failed to activate TET in primary mononuclear cells isolated from myeloid neoplasia patients with TET2 mutations. Consistent with the in-vitro observation, we found that ascorbate treatment in physiologically relevant doses has no significant effect in syngeneic murine models (p=0.1). TET-inactivation is a complex phenomenon that is controlled by context-dependent post-translational modifications including lysine acetylation by acetyltransferases and class I and II deacetylases. Therefore, the anti-leukemic effect of the supraphysiological doses of ascorbate in humans and mice leukemia models may not be dependent on TET activation by ascorbate. On the other hand, a comprehensive analysis of the configurations of TET2 MT in myeloid neoplasia (n= 2617) demonstrated a remarkable exclusivity with 2-hydroxyglutarate (2-HG) producing neomorphic IDH1/2 MT. Ectopic inducible expression of IDH1/2 MT induced synthetic lethality of malignant TET2 MT cells. Therefore, themutual exclusivity of TET2 MT and neomorphic IDH1/2 MT is due to synthetic lethality caused by 2-HG production. In addition, we demonstrate that sequential deletion of TET1 and TET3 leads to growth arrest in cellular models, which has never been observed in any myeloid malignancies. Altogether, these observations suggest that malignant TET2 mutant myeloid cells may be vulnerable to inhibition of residual TET-activity coming from TET1 and TET3. Therefore, we synthesized TET-specific inhibitor on 2HG scaffold using iterative computer-aided design, characterized in cell-free as well as cell culture model systems, and selected TETi76 with no cytotoxic effect in normal bone marrow-derived CD34 + cells. TETi76 selectively inhibits TET-dioxygenase activity with IC50 of 1.5, 9.4, and 8.8 μmol/L for TET1/2/3, and it restricts clonal outgrowth of TET2 MT both in vitro and in vivo in malignant and nonmalignant clonal hematopoiesis of indeterminate potential (CHIP). Conclusion: Taken together, here we demonstrated that anti-cancer activity of ascorbate may not come from its role as a TET activator and that a minimum level of TET-dioxygenase activity is required for cell survival, rendering TET2 -mutant malignant cells selectively vulnerable to inhibitors of TET-function. Disclosures Maciejewski: Regeneron: Consultancy; Novartis: Consultancy; Bristol Myers Squibb/Celgene: Consultancy; Alexion: Consultancy.


Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1661 ◽  
Author(s):  
Trang T. T. Nguyen ◽  
Yiru Zhang ◽  
Enyuan Shang ◽  
Chang Shu ◽  
Catarina M. Quinzii ◽  
...  

The heterogeneity of glioblastomas, the most common primary malignant brain tumor, remains a significant challenge for the treatment of these devastating tumors. Therefore, novel combination treatments are warranted. Here, we showed that the combined inhibition of TRAP1 by gamitrinib and histone deacetylases (HDAC1/HDAC2) through romidepsin or panobinostat caused synergistic growth reduction of established and patient-derived xenograft (PDX) glioblastoma cells. This was accompanied by enhanced cell death with features of apoptosis and activation of caspases. The combination treatment modulated the levels of pro- and anti-apoptotic Bcl-2 family members, including BIM and Noxa, Mcl-1, Bcl-2 and Bcl-xL. Silencing of Noxa, BAK and BAX attenuated the effects of the combination treatment. At the metabolic level, the combination treatment led to an enhanced reduction of oxygen consumption rate and elicited an unfolded stress response. Finally, we tested whether the combination treatment of gamitrinib and panobinostat exerted therapeutic efficacy in PDX models of glioblastoma (GBM) in mice. While single treatments led to mild to moderate reduction in tumor growth, the combination treatment suppressed tumor growth significantly stronger than single treatments without induction of toxicity. Taken together, we have provided evidence that simultaneous targeting of TRAP1 and HDAC1/2 is efficacious to reduce tumor growth in model systems of glioblastoma.


Cancers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2137
Author(s):  
Enyuan Shang ◽  
Trang T. T. Nguyen ◽  
Chang Shu ◽  
Mike-Andrew Westhoff ◽  
Georg Karpel-Massler ◽  
...  

Apoptotic resistance remains a hallmark of glioblastoma (GBM), the most common primary brain tumor in adults, and a better understanding of this process may result in more efficient treatments. By utilizing chromatin immunoprecipitation with next-generation sequencing (CHIP-seq), we discovered that GBMs harbor a super enhancer around the Mcl-1 locus, a gene that has been known to confer cell death resistance in GBM. We utilized THZ1, a known super-enhancer blocker, and BH3-mimetics, including ABT263, WEHI-539, and ABT199. Combined treatment with BH3-mimetics and THZ1 led to synergistic growth reduction in GBM models. Reduction in cellular viability was accompanied by significant cell death induction with features of apoptosis, including disruption of mitochondrial membrane potential followed by activation of caspases. Mechanistically, THZ1 elicited a profound disruption of the Mcl-1 enhancer region, leading to a sustained suppression of Mcl-1 transcript and protein levels, respectively. Mechanism experiments suggest involvement of Mcl-1 in the cell death elicited by the combination treatment. Finally, the combination treatment of ABT263 and THZ1 resulted in enhanced growth reduction of tumors without induction of detectable toxicity in two patient-derived xenograft models of GBM in vivo. Taken together, these findings suggest that combined epigenetic targeting of Mcl-1 along with Bcl-2/Bcl-xL is potentially therapeutically feasible.


2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii288-iii289
Author(s):  
Nicholas Vitanza ◽  
Matt Biery ◽  
Carrie Myers ◽  
Eric Ferguson ◽  
Giulia Park ◽  
...  

Abstract As the majority of diffuse intrinsic pontine glioma (DIPG) have H3K27M mutations, epigenetic-targeting agents have been studied, though evaluations have been limited by their model systems, untranslatable drug concentrations, and/or evasive mechanisms of action. To develop a more translational model, we used biopsy samples from newly diagnosed DIPG patients to create treatment-naïve in vitro and in vivo models (molecular aberrations in parentheses), including PBT-09FH (H3FA3, PI3KCA), PBT-22FH (H3F3A, TP53), PBT-24FH (PMS2), and PBT-27FH (HIST1H3B, TP53, NTRK2). Models demonstrated radiation-resistance similar to the patient from whom the culture was generated, supporting the models’ relevance (e.g. cell viability after 8 Gy was 36%, 81%, 71%, and 61% in PBT-09FH, -22FH, -24FH, and -27FH, respectively, compared to 7% in the medulloblastoma model MED-411FH). We evaluated cell viability and apoptosis following treatment with a panel of HDAC inhibitors, identifying the low nanomolar IC50 of quisinostat (~50 nM) and romidepsin (~5 nM). While RNA expression changes induced by 100 nM panobinostat and quisinostat included shared overexpression of the top 20/25 genes (e.g. FSTL5, ITIH5) and shared downregulation of the top 22/25 (e.g. GPR37L1, HEPACAM), only 9/25 were downregulated by panobinostat, quisinostat, and romidepsin (e.g. C21orf62, IFIT2), identifying these as potential vulnerabilities or biomarkers of lethal HDAC inhibition. Mass-spectrometry (LC-MS) demonstrated panobinostat as the greatest acetylator of cortactin, potentially related to thrombocytopenia. While PBT-09 flank models demonstrated quisinostat’s on-target acetylation and efficacy, orthotopic xenograft models did not, supporting our model’s intact blood-brain barrier and emphasizing the need for CNS penetrant versions of potentially efficacious agents.


2021 ◽  
Vol 5 (19) ◽  
pp. 3776-3788
Author(s):  
Liang Zhou ◽  
Yu Zhang ◽  
Mark B. Meads ◽  
Yun Dai ◽  
Yanxia Ning ◽  
...  

Abstract Interactions between the inhibitor of apoptosis protein antagonist LCL161 and the histone deacetylase inhibitor panobinostat (LBH589) were examined in human multiple myeloma (MM) cells. LCL161 and panobinostat interacted synergistically to induce apoptosis in diverse MM cell lines, including those resistant to bortezomib (PS-R). Similar interactions were observed with other histone deacetylase inhibitors (MS-275) or inhibitors of apoptosis protein antagonists (birinapant). These events were associated with downregulation of the noncanonical (but not the canonical) NF-κB pathway and activation of the extrinsic, caspase-8–related apoptotic cascade. Coexposure of MM cells to LCL161/LBH589 induced TRAF3 upregulation and led to TRAF2 and NIK downregulation, diminished expression of BCL-XL, and induction of γH2A.X. Ectopic expression of TRAF2, NIK, or BCL-XL, or short hairpin RNA TRAF3 knock-down, significantly reduced LCL161/LBH589 lethality, as did ectopic expression of dominant-negative FADD. Stromal/microenvironmental factors failed to diminish LCL161/LBH589–induced cell death. The LCL161/LBH589 regimen significantly increased cell killing in primary CD138+ cells (N = 31) and was particularly effective in diminishing the primitive progenitor cell–enriched CD138–/19+/20+/27+ population (N = 23) but was nontoxic to normal CD34+ cells. Finally, combined LCL161/LBH589 treatment significantly increased survival compared with single-agent treatment in an immunocompetent 5TGM1 murine MM model. Together, these findings argue that LCL161 interacts synergistically with LBH589 in MM cells through a process involving inactivation of the noncanonical NF-κB pathway and activation of the extrinsic apoptotic pathway, upregulation of TRAF3, and downregulation of TRAF2/BCL-XL. Notably, this regimen overcomes various forms of resistance, is active against primary MM cells, and displays significant in vivo activity. This strategy warrants further consideration in MM.


2006 ◽  
Vol 26 (17) ◽  
pp. 6395-6402 ◽  
Author(s):  
Min Gyu Lee ◽  
Christopher Wynder ◽  
Daniel A. Bochar ◽  
Mohamed-Ali Hakimi ◽  
Neil Cooch ◽  
...  

ABSTRACT Histone deacetylase (HDAC) inhibitors are a promising class of anticancer agents for the treatment of solid and hematological malignancies. The precise mechanism by which HDAC inhibitors mediate their effects on tumor cell growth, differentiation, and/or apoptosis is the subject of intense research. Previously we described a family of multiprotein complexes that contain histone deacetylase 1/2 (HDAC1/2) and the histone demethylase BHC110 (LSD1). Here we show that HDAC inhibitors diminish histone H3 lysine 4 (H3K4) demethylation by BHC110 in vitro. In vivo analysis revealed an increased H3K4 methylation concomitant with inhibition of nucleosomal deacetylation by HDAC inhibitors. Reconstitution of recombinant complexes revealed a functional connection between HDAC1 and BHC110 only when nucleosomal substrates were used. Importantly, while the enzymatic activity of BHC110 is required to achieve optimal deacetylation in vitro, in vivo analysis following ectopic expression of an enzymatically dead mutant of BHC110 (K661A) confirmed the functional cross talk between the demethylase and deacetylase enzymes. Our studies not only reveal an intimate link between the histone demethylase and deacetylase enzymes but also identify histone demethylation as a secondary target of HDAC inhibitors.


2020 ◽  
Vol 19 (1) ◽  
Author(s):  
You Shuai ◽  
Zhonghua Ma ◽  
Weitao Liu ◽  
Tao Yu ◽  
Changsheng Yan ◽  
...  

Abstract Background Gastric cancer (GC) is the third leading cause of cancer-related mortality globally. Long noncoding RNAs (lncRNAs) are dysregulated in obvious malignancies including GC and exploring the regulatory mechanisms underlying their expression is an attractive research area. However, these molecular mechanisms require further clarification, especially upstream mechanisms. Methods LncRNA MNX1-AS1 expression in GC tissue samples was investigated via microarray analysis and further determined in a cohort of GC tissues via quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays. Cell proliferation and flow cytometry assays were performed to confirm the roles of MNX1-AS1 in GC proliferation, cell cycle regulation, and apoptosis. The influence of MNX1-AS1 on GC cell migration and invasion was explored with Transwell assays. A xenograft tumour model was established to verify the effects of MNX1-AS1 on in vivo tumourigenesis. The TEAD4-involved upstream regulatory mechanism of MNX1-AS1 was explored through ChIP and luciferase reporter assays. The mechanistic model of MNX1-AS1 in regulating gene expression was further detected by subcellular fractionation, FISH, RIP, ChIP and luciferase reporter assays. Results It was found that MNX1-AS1 displayed obvious upregulation in GC tissue samples and cell lines, and ectopic expression of MNX1-AS1 predicted poor clinical outcomes for patients with GC. Overexpressed MNX1-AS1 expression promoted proliferation, migration and invasion of GC cells markedly, whereas decreased MNX1-AS1 expression elicited the opposite effects. Consistent with the in vitro results, MNX1-AS1 depletion effectively inhibited the growth of xenograft tumour in vivo. Mechanistically, TEAD4 directly bound the promoter region of MNX1-AS1 and stimulated the transcription of MNX1-AS1. Furthermore, MNX1-AS1 can sponge miR-6785-5p to upregulate the expression of BCL2 in GC cells. Meanwhile, MNX1-AS1 suppressed the transcription of BTG2 by recruiting polycomb repressive complex 2 to BTG2 promoter regions. Conclusions Our findings demonstrate that MNX1-AS1 may be able to serve as a prognostic indicator in GC patients and that TEAD4-activatd MNX1-AS1 can promote GC progression through EZH2/BTG2 and miR-6785-5p/BCL2 axes, implicating it as a novel and potent target for the treatment of GC.


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