scholarly journals BRD4-mediated repression of p53 is a target for combination therapy in AML

2020 ◽  
Author(s):  
Anne-Louise Latif ◽  
Ashley Newcombe ◽  
Sha Li ◽  
Kathryn Gilroy ◽  
Neil Robertson ◽  
...  
Keyword(s):  
Broad Spectrum ◽  
Myeloid Leukemia ◽  
Target Genes ◽  
Clinical Activity ◽  
Tumor Suppressor P53 ◽  
Wild Type ◽  
Bet Inhibitors ◽  
P53 Activation ◽  
P53 Target Genes ◽  
Synergistic Toxicity

SummaryAcute Myeloid Leukemia (AML) is a typically-lethal molecularly heterogeneous disease, with few broad-spectrum therapeutic targets. Unusually, most AML retain wild-type TP53, encoding the pro-apoptotic tumor suppressor p53. MDM2 inhibitors (MDM2i), which activate wild-type p53, and BET inhibitors (BETi), targeting the BET-family co-activator BRD4, both show encouraging pre-clinical activity, but limited clinical activity as single agents. Here, we report synergistic toxicity of combined MDM2i and BETi towards AML cell lines, primary human blasts and mouse models, resulting from BETi’s ability to evict an unexpected repressive form of BRD4 from p53 target genes, and hence potentiate MDM2i-induced p53 activation. These results indicate that wild-type TP53 and a transcriptional repressor function of BRD4 together represent a potential broad-spectrum synthetic therapeutic vulnerability for AML.

scholarly journals A Synthetic Lethal Approach to Eradicate AML Via Synergistic Activation of Pro-Apoptotic p53 By MDM2 and BET Inhibitors

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 14-14
Author(s):  
Sha Li ◽  
Anne-Louise Latif ◽  
Ashley Newcombe ◽  
Kathryn Gilrory ◽  
Neil Robertson ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Research Funding ◽  
Target Genes ◽  
Transcriptional Repressor ◽  
Clinical Activity ◽  
Wild Type ◽  
Advisory Committees ◽  
Synthetic Lethal ◽  
Synergistic Activation ◽  
P53 Target Genes

Acute Myeloid Leukemia (AML) is a typically-lethal molecularly heterogeneous disease, with few broad-spectrum therapeutic targets. Unusually compared to many other cancers, over 90% of AML patients retain wild type TP53, encoding pro-apoptotic tumor suppressor p53. However, wild-type p53 functions are frequently suppressed by MDM2, an E3 ubiquitin ligase that targets p53 for proteasomal degradation. MDM2 inhibitors (MDM2i), which activate wild-type p53, show encouraging pre-clinical activity, but limited clinical activity. In an effort to find targets that synergize with p53 activation via MDM2i and minimize toxicity, we performed a cell-based synthetic lethal drug screen and a CRISPR viability screen. These screens identified BRD4 inhibition as a candidate synthetic lethal partner of MDM2i. BRD4 is a member of the Bromodomains and Extraterminal (BET) family of proteins, a transcriptional co-activator and already a candidate AML therapeutic target. Surprisingly, we found inhibition of BRD4 alone induces expression of some of p53 target genes. We unexpectedly reveal that BRD4 binds to p53 target genes and acts as a transcriptional repressor of these genes. Synergistic cell killing by the drug combination (MDM2i + BET inhibitor (BETi)) depends on synergistic activation of p53 target genes, such as PUMA and NOXA, due to simultaneous stabilization of p53 by MDM2i and relief of BRD4-mediated repression by BETi. Our combined therapy of MDM2i and BETi is synergistically lethal to human AML cell lines harboring wild type TP53in vitro, against two mouse models of AML in vivo, and against primary human patient blasts in vitro. Furthermore, we used BET PROTACs to selectively and completely induce degradation of BRD4 in cells. Consistent with results from BETi, BET degraders and MDM2i synergize to suppress cell viability with superior potency. Taken together, our data show BRD4 represses p53-mediated transcription activation and apoptosis in AML. Therefore, co-targeting wild-type TP53 and a transcriptional repressor function of BRD4 represent a novel synthetic lethal vulnerability in AML. Disclosures Latif: AbbVie: Consultancy, Honoraria; Takeda UK: Speakers Bureau; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Kite: Consultancy, Honoraria, Speakers Bureau; Jazz: Consultancy, Honoraria; Daiichi Sankyo: Consultancy, Honoraria. Higgins:Roche: Current Employment, Current equity holder in publicly-traded company, Other: Support of parent study and funding of editorial support. Copland:Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Cyclacel Ltd: Research Funding; Roche: Research Funding; Epizyme: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; Astellas: Speakers Bureau; Gilead: Speakers Bureau.

scholarly journals CK1α ablation in keratinocytes induces p53-dependent, sunburn-protective skin hyperpigmentation

2017 ◽  
Vol 114 (38) ◽  
pp. E8035-E8044 ◽  
Author(s):  
Chung-Hsing Chang ◽  
Che-Jung Kuo ◽  
Takamichi Ito ◽  
Yu-Ya Su ◽  
Si-Tse Jiang ◽  
...  
Keyword(s):  
Target Genes ◽  
Neutralizing Antibody ◽  
Double Knockout ◽  
Melanocyte Stimulating Hormone ◽  
Kit Ligand ◽  
Skin Physiology ◽  
P53 Activation ◽  
P53 Target Genes ◽  
Single Knockout

Casein kinase 1α (CK1α), a component of the β-catenin destruction complex, is a critical regulator of Wnt signaling; its ablation induces both Wnt and p53 activation. To characterize the role of CK1α (encoded byCsnk1a1) in skin physiology, we crossed mice harboring floxedCsnk1a1with mice expressing K14–Cre–ERT2to generate mice in which tamoxifen induces the deletion ofCsnk1a1exclusively in keratinocytes [single-knockout (SKO) mice]. As expected, CK1α loss was accompanied by β-catenin and p53 stabilization, with the preferential induction of p53 target genes, but phenotypically most striking was hyperpigmentation of the skin, importantly without tumorigenesis, for at least 9 mo afterCsnk1a1ablation. The number of epidermal melanocytes and eumelanin levels were dramatically increased in SKO mice. To clarify the putative role of p53 in epidermal hyperpigmentation, we established K14–Cre–ERT2CK1α/p53 double-knockout (DKO) mice and found that coablation failed to induce epidermal hyperpigmentation, demonstrating that it was p53-dependent. Transcriptome analysis of the epidermis revealed p53-dependent up-regulation of Kit ligand (KitL). SKO mice treated with ACK2 (a Kit-neutralizing antibody) or imatinib (a Kit inhibitor) abrogated the CK1α ablation-induced hyperpigmentation, demonstrating that it requires the KitL/Kit pathway. Pro-opiomelanocortin (POMC), a precursor of α-melanocyte–stimulating hormone (α-MSH), was not activated in the CK1α ablation-induced hyperpigmentation, which is in contrast to the mechanism of p53-dependent UV tanning. Nevertheless, acute sunburn effects were successfully prevented in the hyperpigmented skin of SKO mice. CK1α inhibition induces skin-protective eumelanin but no carcinogenic pheomelanin and may therefore constitute an effective strategy for safely increasing eumelanin via UV-independent pathways, protecting against acute sunburn.

scholarly journals Dual inhibition of MDM2 and MDM4 in virus-positive Merkel cell carcinoma enhances the p53 response

2018 ◽  
Vol 116 (3) ◽  
pp. 1027-1032 ◽  
Author(s):  
Donglim Esther Park ◽  
Jingwei Cheng ◽  
Christian Berrios ◽  
Joan Montero ◽  
Marta Cortés-Cros ◽  
...  
Keyword(s):  
Target Genes ◽  
Underlying Mechanism ◽  
T Antigen ◽  
Sequencing Analysis ◽  
Merkel Cell ◽  
Wild Type ◽  
Synergistic Activation ◽  
P53 Response ◽  
P53 Activation ◽  
Small T Antigen

Merkel cell polyomavirus (MCV) contributes to approximately 80% of all Merkel cell carcinomas (MCCs), a highly aggressive neuroendocrine carcinoma of the skin. MCV-positive MCC expresses small T antigen (ST) and a truncated form of large T antigen (LT) and usually contains wild-type p53 (TP53) and RB (RB1). In contrast, virus-negative MCC contains inactivating mutations in TP53 and RB1. While the MCV-truncated LT can bind and inhibit RB, it does not bind p53. We report here that MCV LT binds to RB, leading to increased levels of ARF, an inhibitor of MDM2, and activation of p53. However, coexpression of ST reduced p53 activation. MCV ST recruits the MYC homologue MYCL (L-Myc) to the EP400 chromatin remodeler complex and transactivates specific target genes. We observed that depletion of EP400 in MCV-positive MCC cell lines led to increased p53 target gene expression. We suspected that the MCV ST–MYCL–EP400 complex could functionally inactivate p53, but the underlying mechanism was not known. Integrated ChIP and RNA-sequencing analysis following EP400 depletion identified MDM2 as well as CK1α, an activator of MDM4, as target genes of the ST–MYCL–EP400 complex. In addition, MCV-positive MCC cells expressed high levels of MDM4. Combining MDM2 inhibitors with lenalidomide targeting CK1α or an MDM4 inhibitor caused synergistic activation of p53, leading to an apoptotic response in MCV-positive MCC cells and MCC-derived xenografts in mice. These results support dual targeting of MDM2 and MDM4 in virus-positive MCC and other p53 wild-type tumors.

scholarly journals FLIP(L) determines p53 induced life or death

2019 ◽  
Author(s):  
Andrea Lees ◽  
Alexander J. McIntyre ◽  
Fiammetta Falcone ◽  
Nyree T. Crawford ◽  
Christopher McCann ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Cell Fate ◽  
Target Genes ◽  
Hdac Inhibitors ◽  
Caspase 8 ◽  
Cycle Arrest ◽  
P53 Activation ◽  
P53 Target Genes ◽  
Mdm2 Inhibitor

AbstractHow p53 differentially activates cell cycle arrest versus cell death remains poorly understood. Here, we demonstrate that upregulation of canonical pro-apoptotic p53 target genes in colon cancer cells imposes a critical dependence on the long splice form of the caspase-8 regulator FLIP (FLIP(L)), which we identify as a direct p53 transcriptional target. Inhibiting FLIP(L) expression with siRNA or Class-I HDAC inhibitors promotes apoptosis in response to p53 activation by the MDM2 inhibitor Nutlin-3A, which otherwise predominantly induces cell-cycle arrest. When FLIP(L) upregulation is inhibited, apoptosis is induced in response to p53 activation via a novel ligand-independent TRAIL-R2/caspase-8 complex, which, by activating BID, induces mitochondrial-mediated apoptosis. Notably, FLIP(L) depletion inhibits p53-induced expression of the cell cycle regulator p21 and enhances p53-mediated upregulation of PUMA, with the latter activating mitochondrial-mediated apoptosis in FLIP(L)-depleted, Nutlin-3A-treated cells lacking TRAIL-R2/caspase-8. Thus, we report two previously undescribed, novel FLIP(L)-dependent mechanisms that determine cell fate following p53 activation.

scholarly journals Phase 1b study of the MDM2 inhibitor AMG 232 with or without trametinib in relapsed/refractory acute myeloid leukemia

2019 ◽  
Vol 3 (13) ◽  
pp. 1939-1949 ◽  
Author(s):  
Harry P. Erba ◽  
Pamela S. Becker ◽  
Paul J. Shami ◽  
Michael R. Grunwald ◽  
Donna L. Flesher ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Target Genes ◽  
Phase 1 ◽  
Maximum Tolerated Dose ◽  
Clinical Activity ◽  
Open Label ◽  
Refractory Acute Myeloid Leukemia ◽  
Higher Doses ◽  
Acute Myeloid

AbstractThis open-label, phase 1 study evaluated the safety, pharmacokinetics, and maximum tolerated dose of AMG 232, an investigational oral, selective mouse double minute 2 homolog inhibitor in relapsed/refractory acute myeloid leukemia (AML). AMG 232 was administered orally once daily for 7 days every 2 weeks (7 on/off) at 60, 120, 240, 360, 480, or 960 mg as monotherapy (arm 1) or at 60 mg with trametinib 2 mg (arm 2). Dose-limiting toxicities (DLTs), adverse events (AEs), pharmacokinetics, clinical and pharmacodynamic response, and expression of p53 target genes were assessed. All 36 patients received AMG 232. No DLTs occurred in arm 1, and 360 mg was the highest test dose; dose escalation was halted due to gastrointestinal AEs at higher doses. One of ten patients in arm 2 had a DLT (grade 3 fatigue); 60 mg was the highest dose tested with trametinib. Common treatment-related AEs (any grade) included nausea (58%), diarrhea (56%), vomiting (33%), and decreased appetite (25%). AMG 232 exhibited linear pharmacokinetics unaffected by coadministration with trametinib. Serum macrophage inhibitor cytokine-1 and bone marrow expression of BAX, PUMA, P21, and MDM2 increased during treatment. Of 30 evaluable patients, 1 achieved complete remission, 4 had morphologic leukemia-free state, and 1 had partial remission. Four of 13 (31%) TP53-wild-type patients and 0 of 3 (0%) TP53-mutant patients were responders. AMG 232 was associated with gastrointestinal AEs at higher doses but had acceptable pharmacokinetics, on-target effects, and promising clinical activity warranting further investigation in patients with relapsed/refractory AML. This trial was registered at www.clinicaltrials.gov as #NCT02016729.

MAPK Signaling Pathway was Dysregulated in Acute Myeloid Leukemia with RUNX1 Mutations

2021 ◽  
Author(s):  
Mingmin he ◽  
Xiongwei Cai ◽  
Yuanyuan Zeng
Keyword(s):  
Acute Myeloid Leukemia ◽  
Signaling Pathway ◽  
Myeloid Leukemia ◽  
Target Genes ◽  
Mapk Signaling ◽  
Mapk Signaling Pathway ◽  
Functional Enrichment ◽  
Wild Type ◽  
The Relationship ◽  
Acute Myeloid

Abstract The purpose of this study was to investigate the relationship between RUNX1 mutations and MAPK signaling pathway in acute myeloid leukemia (AML). In this study, we analyzed miRNA expression with 5 mutant RUNX1 and 9 wild-type RUNX1 cases from TCGA database of AML. Six miRNAs were differently expressed with significance, and three of them were related to overall survival. Predicted target genes of these 3 miRNAs were highly enriched in MAPK signaling pathway by functional enrichment with miRWalk3.0. Besides, genes among RUNX1 associated genes directly regulated by RUNX1 were involved in MAPK signaling pathway, too. Taken together, we demonstrate three DEmiRNAs and three genes correlated to RUNX1 were correlated with prognosis in AML, and RUNX1 modulated MAPK signaling pathway in AML.

scholarly journals Disruption of entire Cables2 locus leads to embryonic lethality by diminished Rps21 gene expression and enhanced p53 pathway

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Tra Thi Huong Dinh ◽  
Hiroyoshi Iseki ◽  
Seiya Mizuno ◽  
Saori Iijima-Mizuno ◽  
Yoko Tanimoto ◽  
...  
Keyword(s):  
Target Genes ◽  
Embryonic Lethality ◽  
Wild Type ◽  
Wild Type Embryo ◽  
Targeted Disruption ◽  
P53 Pathway ◽  
Enzyme Substrate ◽  
Exon 1 ◽  
P53 Target Genes

In vivo function of CDK5 and Abl enzyme substrate 2 (Cables2), belonging to the Cables protein family, is unknown. Here, we found that targeted disruption of the entire Cables2 locus (Cables2d) caused growth retardation and enhanced apoptosis at the gastrulation stage and then induced embryonic lethality in mice. Comparative transcriptome analysis revealed disruption of Cables2, 50% down-regulation of Rps21 abutting on the Cables2 locus, and up-regulation of p53-target genes in Cables2d gastrulas. We further revealed the lethality phenotype in Rps21-deleted mice and unexpectedly, the exon 1-deleted Cables2 mice survived. Interestingly, chimeric mice derived from Cables2d ESCs carrying exogenous Cables2 and tetraploid wild-type embryo overcame gastrulation. These results suggest that the diminished expression of Rps21 and the completed lack of Cables2 expression are intricately involved in the embryonic lethality via the p53 pathway. This study sheds light on the importance of Cables2 locus in mouse embryonic development.

scholarly journals The in vivo gene expression signature of oxidative stress

2008 ◽  
Vol 34 (1) ◽  
pp. 112-126 ◽  
Author(s):  
Eun-Soo Han ◽  
Florian L. Muller ◽  
Viviana I. Pérez ◽  
Wenbo Qi ◽  
Huiyun Liang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Gene Expression ◽  
Oxidative Damage ◽  
Target Genes ◽  
Wild Type ◽  
Antioxidant Genes ◽  
Genetic Ablation ◽  
Expression Response ◽  
P53 Target Genes

How higher organisms respond to elevated oxidative stress in vivo is poorly understood. Therefore, we measured oxidative stress parameters and gene expression alterations (Affymetrix arrays) in the liver caused by elevated reactive oxygen species induced in vivo by diquat or by genetic ablation of the major antioxidant enzymes CuZn-superoxide dismutase ( Sod1) and glutathione peroxidase-1 ( Gpx1). Diquat (50 mg/kg) treatment resulted in a significant increase in oxidative damage within 3–6 h in wild-type mice without any lethality. In contrast, treatment of Sod1−/− or Gpx1−/− mice with a similar concentration of diquat resulted in a significant increase in oxidative damage within an hour of treatment and was lethal, i.e., these mice are extremely sensitive to the oxidative stress generated by diquat. The expression response to elevated oxidative stress in vivo does not involve an upregulation of classic antioxidant genes, although long-term oxidative stress in Sod1−/− mice leads to a significant upregulation of thiol antioxidants (e.g., Mt1, Srxn1, Gclc, Txnrd1), which appears to be mediated by the redox-sensitive transcription factor Nrf2. The main finding of our study is that the common response to elevated oxidative stress with diquat treatment in wild-type, Gpx1−/−, and Sod1−/− mice and in untreated Sod1−/− mice is an upregulation of p53 target genes ( p21, Gdf15, Plk3, Atf3, Trp53inp1, Ddit4, Gadd45a, Btg2, Ndrg1). A retrospective comparison with previous studies shows that induction of these p53 target genes is a conserved expression response to oxidative stress, in vivo and in vitro, in different species and different cells/organs.

scholarly journals Simultaneous activation of p53 and inhibition of XIAP enhance the activation of apoptosis signaling pathways in AML

Blood ◽  
2010 ◽  
Vol 115 (2) ◽  
pp. 306-314 ◽  
Author(s):  
Bing Z. Carter ◽  
Duncan H. Mak ◽  
Wendy D. Schober ◽  
Erich Koller ◽  
Clemencia Pinilla ◽  
...  
Keyword(s):  
Cell Death ◽  
Myeloid Leukemia ◽  
Wild Type ◽  
Combination Strategy ◽  
Mdm2 Antagonist ◽  
P53 Activation ◽  
Simultaneous Activation ◽  
Murine Double Minute ◽  
Caspase 6 ◽  
Induced Apoptosis

Abstract Activation of p53 by murine double minute (MDM2) antagonist nutlin-3a or inhibition of X-linked inhibitor of apoptosis (XIAP) induces apoptosis in acute myeloid leukemia (AML) cells. We demonstrate that concomitant inhibition of MDM2 by nutlin-3a and of XIAP by small molecule antagonists synergistically induced apoptosis in p53 wild-type OCI-AML3 and Molm13 cells. Knockdown of p53 by shRNA blunted the synergy, and down-regulation of XIAP by antisense oligonucleotide (ASO) enhanced nutlin-3a–induced apoptosis, suggesting that the synergy was mediated by p53 activation and XIAP inhibition. This is supported by data showing that inhibition of both MDM2 and XIAP by their respective ASOs induced significantly more cell death than either ASO alone. Importantly, p53 activation and XIAP inhibition enhanced apoptosis in blasts from patients with primary AML, even when the cells were protected by stromal cells. Mechanistic studies demonstrated that XIAP inhibition potentiates p53-induced apoptosis by decreasing p53-induced p21 and that p53 activation enhances XIAP inhibition-induced cell death by promoting mitochondrial release of second mitochondria-derived activator of caspases (SMAC) and by inducing the expression of caspase-6. Because both XIAP and p53 are presently being targeted in ongoing clinical trials in leukemia, the combination strategy holds promise for expedited translation into the clinic.

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