Combination of Venetoclax and CUDC-907 Shows Superior Antileukemic Activity Against Acute Myeloid Leukemia Ex Vivo

Abstract Overall survival rates for adults and children with acute myeloid leukemia (AML) remain unacceptably low. Resistance to chemotherapy is the major factor contributing to such dismal overall survival rates. Chemoresistance in leukemia cell line models has been associated with overexpression of the anti-apoptotic Bcl-2 family members. As such, small molecule Bcl-2 inhibitors represent a promising strategy for treating AML. Venetoclax (ABT-199) is a Bcl-2-selective inhibitor that has demonstrated promising antileukemic activity against AML. However, initial resistance to ABT-199 remains a concern. In our most recent study, we identified a novel Mcl-1-mediated intrinsic mechanism of resistance to ABT-199 in AML cells: ABT-199 treatment results in increased sequestration of Bim by Mcl-1, preventing Bim from inducing apoptosis (Niu X, et al. Clinical Cancer Research. 2016; epub ahead of print). We also found that ABT-199 in combination with DNA damaging agents results in enhanced DNA damage and synergistic antileukemic activity against AML cells. Based on these findings, we hypothesized that simultaneously downregulating Mcl-1, upregulating Bim, and enhancing DNA replication stress and/or DNA damage would maximally enhance ABT-199-induced cell death, leading to potent synergistic antileukemic activity against AML. CUDC-907, a dual histone deacetylase inhibitor (HDACI) and PI3K inhibitor, is currently being tested in Phase I and Phase II clinical trials for the treatment of lymphoma, multiple myeloma, and advanced/relapsed solid tumors (www.clinicaltrials.gov). It inactivates both PI3K/AKT and MEK/ERK signaling pathways in different cancer cell types. Inhibition of these pathways has been shown to cause downregulation of Mcl-1 and upregulation of Bim and HDACIs have been demonstrated to downregulate CHK1 and Wee1, as well as upregulate Bim, leading to DNA damage and cell death. Furthermore, CHK1 and Wee1 inhibitors have been shown to cause DNA replication stress through downregulation of ribonucleotide reductase (RNR). Therefore, CUDC-907 would be an ideal compound to combine with ABT-199 to enhance its antileukemic activity against AML. In this study, we investigated the antileukemic activity of CUDC-907 alone and in combination with ABT-199 in both AML cell lines and primary patient samples. CUDC-907 treatment resulted in increased Bim expression and decreased Mcl-1, CHK-1, Wee1, and RRM1 (the regulatory subunit of RNR) expression in both AML cell lines and primary patient samples. Ectopic overexpression of Mcl-1 and shRNA knockdown of Bim demonstrated that both were at least partially involved in CUDC-907-induced apoptosis. Treatment with a CHK1-selective inhibitor LY2603618, the Wee1-selective inhibitor MK-1775, or hydroxyurea (RNR inhibitor) enhanced CUDC-907-induced apoptosis in a synergistic fashion, demonstrating that downregulation of Wee1, CHK1, and RRM1 was also an important contributor to CUDC-907-induced apoptosis. Consistent with our hypothesis, the combination of CUDC-907 and ABT-199 resulted in significantly increased apoptosis compared to single drug treatment and excellent synergy in both AML cell lines (n=6) and primary patient samples (n=18), regardless of their sensitivities to ABT-199. Synergy was also detected when AML cells were treated with CUDC-907 first for 16 h and then followed by ABT-199 treatment for another 8 h. Western blots revealed that combined treatment caused further decrease of Mcl-1, CHK1, and Wee1, while comet assays revealed that the combination caused significantly increased DNA strand breaks in both AML cell lines and primary patient samples. Our results demonstrate that CUDC-907 synergizes with ABT-199 in AML cells, and support the clinical development of the combination of CUDC-907 and ABT-199 in the treatment of AML. Disclosures Yang: Seattle Genetics: Research Funding.

Download Full-text

Voruciclib, an Oral, Selective CDK9 Inhibitor, Enhances Cell Death Induced By the Bcl-2 Selective Inhibitor Venetoclax in Acute Myeloid Leukemia

Blood ◽

10.1182/blood-2018-99-118372 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1361-1361 ◽

Cited By ~ 2

Author(s):

Daniel A Luedtke ◽

Yongwei Su ◽

Holly Edwards ◽

Lisa Polin ◽

Juiwanna Kushner ◽

...

Keyword(s):

Cell Lines ◽

Myeloid Leukemia ◽

Caspase 3 ◽

Combination Index ◽

Survival Rates ◽

Annexin V ◽

Antileukemic Activity ◽

Induction Of Apoptosis ◽

Induced Apoptosis

Abstract Introduction: Patients with acute myeloid leukemia (AML) face overall 5-year survival rates of 65% and 27% for children and adults, respectively, leaving significant room for improvement. Relapse remains a major contributor to such low overall survival rates, and leukemic stem cells (LSCs) that survive treatment are believed to be responsible for AML relapse. The anti-apoptotic protein Bcl-2 is overexpressed in bulk AML cells and LSCs and is associated with poor clinical outcomes. Thus, Bcl-2 represents a promising therapeutic target for the treatment of AML. Venetoclax (ABT-199) is a selective Bcl-2 inhibitor that has shown great potential for treating a number of malignancies, including AML. Venetoclax inhibits Bcl-2, preventing it from sequestering pro-apoptotic Bcl-2 family protein Bim, leading to Bim activated Bax/Bak, resulting in apoptosis. However, Mcl-1 can also sequester Bim and prevent apoptosis. We previously showed that directly targeting Mcl-1 can enhance the antileukemic activity of venetoclax (Luedtke DA, et al. Signal Transduct Target Ther. Apr 2017). Alternatively, we proposed that indirect targeting of Mcl-1 may preserve or enhance the antileukemic activity of venetoclax, and prevent resistance resulting from Mcl-1. It has been reported that inhibition of CDK9 can downregulate cell survival genes regulated by superenhancers, including Mcl-1, MYC, and Cyclin D1. One CDK9 inhibitor in clinical development, flavopiridol (alvocidib), has progressed to phase II clinical trials in AML. However, off target effects and dose-limiting toxicities remain a concern. Voruciclib is an oral, selective CDK inhibitor differentiated by its potent inhibition of CDK9 as compared to other CDK inhibitors. This selectivity may potentially circumvent toxicities resulting from inhibition of non-CDK targets like MAK and ICK that are inhibited by flavopiridol. Voruciclib has been shown in vitro to promote apoptosis and decrease Mcl-1 expression levels in chronic lymphocytic leukemia (CLL) cells (Paiva C, et al. PLOS One. Nov 2015) and inhibit tumor growth in mouse xenograft models of diffuse large B-cell lymphoma (DLBCL) in combination with venetoclax (Dey J. et al Scientific Reports. Dec 2017). Based on these data, voruciclib may downregulate Mcl-1 in AML cells and therefore synergistically enhance the antileukemic activity of venetoclax. Methods/Results: Culturing AML cell lines (THP-1, U937, MOLM-13, MV4-11, and OCI-AML3) and primary patient samples with various concentrations of voruciclib resulted in a concentration-dependent increase in Annexin V+ cells (2 μM voruciclib induced 13.8-55.8% Annexin V+ cells) along with increased levels of cleaved caspase 3 and PARP, demonstrating that voruciclib induces apoptosis in AML cells. Next, we tested the combination of voruciclib and venetoclax in AML cell lines and primary AML patient samples at clinically achievable concentrations. Annexin V/PI staining, flow cytometry analysis, and combination index calculation (using CalcuSyn software) revealed synergistic induction of apoptosis by voruciclib and venetoclax combination (combination index values for MV4-11, U937, THP-1, and MOLM-13 cells were <0.73; treatment with 2 µM voruciclib and venetoclax for 24 h resulted in >80% apoptosis). Importantly, synergy was observed in both venetoclax sensitive and resistant cell lines. This was accompanied by increased cleavage of caspase 3 and PARP. Lentiviral shRNA knockdown of Bak and Bax partially rescued AML cells from voruciclib-induced apoptosis, showing that voruciclib induces apoptosis at least partially through the intrinsic apoptosis pathway. However, Bak and Bax knockdown had little to no effect on induction of apoptosis by the combination treatment, indicating that there might be other molecular mechanisms underlying the synergistic interaction between the two agents. Treatment with the pan-caspase inhibitor Z-VAD-FMK partially rescued cells from combination treatment induced-apoptosis. Discussion: Collectively, these results demonstrate that voruciclib and venetoclax synergistically induce apoptosis in AML cells in vitro and reverse venetoclax resistance. Further studies to determine the mechanism of action and in vivo efficacy of this promising combination in AML xenografts and PDX models are underway. Disclosures Ge: MEI Pharma: Research Funding.

Download Full-text

Inhibition of CHK1 Enhances Cell Death Induced By the Bcl-2-Selective Inhibitor ABT-199 in Acute Myeloid Leukemia Cells

Blood ◽

10.1182/blood.v126.23.2469.2469 ◽

2015 ◽

Vol 126 (23) ◽

pp. 2469-2469

Author(s):

Jianyun Zhao ◽

Xiaojia Niu ◽

Holly Edwards ◽

Yue Wang ◽

Jeffrey W Taub ◽

...

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Acute Myeloid Leukemia ◽

Cell Lines ◽

Myeloid Leukemia ◽

Selective Inhibitor ◽

Intrinsic Resistance ◽

Apoptotic Protein ◽

Wide Range ◽

Acute Myeloid

Abstract Acute myeloid leukemia (AML) remains a challenging disease to treat in both pediatric and adult populations. Resistance to cytarabine (ara-C) and anthracycline [e.g., daunorubicin (DNR)]-based chemotherapy is a major cause of treatment failure in this disease. Therefore, more effective therapies are urgently needed to improve treatment outcome of AML patients. Anti-apoptotic Bcl-2 family proteins play key roles in the apoptosis pathway. Overexpression of these proteins is associated with chemoresistance and poor clinical outcome. Thus, much attention has been focused on inhibition of the anti-apoptotic Bcl-2 family proteins for the treatment of various malignancies. ABT-199 is a selective Bcl-2 inhibitor that has demonstrated promising results in CLL, as well as other malignancies including AML. We previously demonstrated that ABT-199 has a wide range of activity in AML cells. In addition, we have also identified that the anti-apoptotic protein Mcl-1, in conjunction with the pro-apoptotic protein Bim, is a key player in resistance to ABT-199 in AML cells. Thus, combining ABT-199 with agents that downregulate Mcl-1 could overcome the intrinsic resistance to ABT-199. Checkpoint kinase 1 (CHK1) is a protein kinase which plays a central role in the DNA damage response (DDR). The DDR represents a complex network of multiple signaling pathways involving cell cycle checkpoints, DNA repair, transcriptional programs, and apoptosis, through which cells maintain genomic integrity following various endogenous or environmental stresses. Inhibition of CHK1 has been demonstrated to induce DNA damage. We and others have also demonstrated that DNA damage results in downregulation of Mcl-1. Thus, it is conceivable that targeting CHK1 may enhance the cytotoxic effects of ABT-199 on AML cells through downregulation of Mcl-1. In this study, we investigated the combination of LY2603618, a CHK1-selective inhibitor, and the Bcl-2 inhibitor ABT-199 in AML cell lines and primary patient samples. We demonstrated that LY2603618 inhibited proliferation of AML cell lines (n=11) and diagnostic blasts (n=26). Interestingly, all 11 AML cell lines and 23 out of the 26 primary AML patient samples tested showed a LY2603618 IC50 lower than the Cmax of LY2603618 (~9 µM) determined in Phase I clinical studies. Annexin V and propidium iodide (PI) staining and flow cytometry analyses revealed that LY2603618 induced Bak-dependent apoptosis in AML cells. As expected, treatment of AML cells with LY2603618 resulted in abolishment of G2 cell cycle check point and DNA double strand breaks (DSBs), which could be, at least partially, blocked by a CDK inhibitor, roscovitine. LY2603618 treatment also resulted in downregulation of Mcl-1, which coincided with the initiation of apoptosis. Overexpression of Mcl-1 in AML cells significantly attenuated apoptosis induced by LY2603618, confirming the critical role of Mcl-1 in apoptosis induced by the agent. Consistent with our hypothesis, simultaneous combination of LY2603618 and ABT-199 resulted in synergistic induction of apoptosis in both AML cell lines and primary patient samples. Our results demonstrate that LY2603618 synergizes with ABT-199 in AML cells. Our findings provide new insights into overcoming the mechanism of ABT-199 resistance in AML cells and support the clinical development of the combination of ABT-199 and CHK1 inhibitors. Disclosures No relevant conflicts of interest to declare.

Download Full-text

The Novel Dihydroorotate Dehydrogenase (DHODH) Inhibitor PTC299 Inhibit De Novo Pyrimidine Synthesis with Broad Anti-Leukemic Activity Against Acute Myeloid Leukemia

Blood ◽

10.1182/blood-2020-139940 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 8-9

Author(s):

Sujan Piya ◽

Marla Weetall ◽

Josephine Sheedy ◽

Balmiki Ray ◽

Huaxian Ma ◽

...

Keyword(s):

Dna Damage ◽

Acute Myeloid Leukemia ◽

Cell Lines ◽

Myeloid Leukemia ◽

Research Funding ◽

De Novo ◽

Dihydroorotate Dehydrogenase ◽

Nucleotide Synthesis ◽

Inhibition Of Proliferation ◽

Acute Myeloid

Introduction: Acute myeloid leukemia (AML) is characterized by both aberrant proliferation and differentiation arrest at hematopoietic progenitor stages 1,2. AML relies upon de novo nucleotide synthesis to meet a dynamic metabolic landscape and to provide a sufficient supply of nucleotides and other macromolecules 3,4. Hence, we hypothesized that inhibition of de novo nucleotide synthesis would lead to depletion of the nucleotide pool and pyrimidine starvation in leukemic cells compared to their non-malignant counterparts and impact proliferative and differentiation inhibition pathways. PTC299 is an inhibitor of dihydroorotate dehydrogenase (DHODH), a rate limiting enzyme for de novo pyrimidine nucleotide synthesis that is currently in a clinical trial for the treatment of AML. Aim: We investigated the pre-clinical activity of PTC299 against AML in primary AML blasts and cytarabine-resistant cell lines. To confirm that PTC299 effects are due to inhibition of de novo pyrimidine nucleotide synthesis for leukemic growth, we specifically tested the impact of uridine and orotate rescue. In addition, a comprehensive analysis of alteration of metabolic signaling in PI3K/AKT pathways, apoptotic signatures and DNA damage responses were analyzed by Mass cytometry based proteomic analysis (CyTOF) and immunoblotting. The potential clinical relevance of DHODH inhibition was confirmed in an AML-PDX model. Results: The IC50s for all tested cell lines (at 3 day) and primary blasts (at 5-7 day) were in a very low nanomolar range: OCI-AML3 -4.43 nM, HL60 -59.7 nM and primary samples -18-90 nM. Treatment of AML in cytarabine-resistant cells demonstrated that PTC299 induced apoptosis, differentiation, and reduced proliferation with corresponding increase in Annexin V and CD14 positive cells (Fig.1). PTC299-induced apoptosis and inhibition of proliferation was rescued by uridine and orotate. To gain more mechanistic insights, we used an immunoblotting and mass cytometry (CyTOF) based approach to analyze changes in apoptotic and cell signaling proteins in OCI-AML3 cells. Apoptotic pathways were induced (cleaved PARP, cleaved Caspase-3) and DNA damage responses (TP53, γH2AX) and the PI3/AKT pathway were downregulated in response to PTC299. In isogenic cell lines, p53-wildtype cells were sustained and an increased DNA damage response with corresponding increase in apoptosis in comparison to p53-deficient cells was shown. (Fig.2) In a PDX mouse model of human AML, PTC299 treatment improved survival compared to mice treated with vehicle (median survival 40 days vs. 30 days, P=0.0002) (Fig.3). This corresponded with a reduction in the bone marrow burden of leukemia with increased expression of differentiation markers in mice treated with PTC299 (Fig.3). Conclusion: PTC299 is a novel dihydroorotate dehydrogenase (DHODH) inhibitor that triggers differentiation, apoptosis and/or inhibition of proliferation in AML and is being tested in a clinical trials for the treatment of acute myeloid malignancies. Reference: 1. Thomas D, Majeti R. Biology and relevance of human acute myeloid leukemia stem cells. Blood 2017; 129(12): 1577-1585. e-pub ahead of print 2017/02/06; doi: 10.1182/blood-2016-10-696054 2. Quek L, Otto GW, Garnett C, Lhermitte L, Karamitros D, Stoilova B et al. Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage. The Journal of experimental medicine 2016; 213(8): 1513-1535. e-pub ahead of print 2016/07/06; doi: 10.1084/jem.20151775 3. Villa E, Ali ES, Sahu U, Ben-Sahra I. Cancer Cells Tune the Signaling Pathways to Empower de Novo Synthesis of Nucleotides. Cancers (Basel) 2019; 11(5). e-pub ahead of print 2019/05/22; doi: 10.3390/cancers11050688 4. DeBerardinis RJ, Chandel NS. Fundamentals of cancer metabolism. Sci Adv 2016; 2(5): e1600200. e-pub ahead of print 2016/07/08; doi: 10.1126/sciadv.1600200 Disclosures Weetall: PTC Therapeutic: Current Employment. Sheedy:PTC therapeutics: Current Employment. Ray:PTC Therapeutics Inc.: Current Employment. Konopleva:Genentech: Consultancy, Research Funding; Rafael Pharmaceutical: Research Funding; Ablynx: Research Funding; Ascentage: Research Funding; Agios: Research Funding; Kisoji: Consultancy; Eli Lilly: Research Funding; AstraZeneca: Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; AbbVie: Consultancy, Research Funding; Calithera: Research Funding; Cellectis: Research Funding; Amgen: Consultancy; Stemline Therapeutics: Consultancy, Research Funding; Forty-Seven: Consultancy, Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Sanofi: Research Funding. Andreeff:Amgen: Research Funding; Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy; Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees. Borthakur:BioLine Rx: Consultancy; BioTherix: Consultancy; Nkarta Therapeutics: Consultancy; Treadwell Therapeutics: Consultancy; Xbiotech USA: Research Funding; Polaris: Research Funding; AstraZeneca: Research Funding; BMS: Research Funding; BioLine Rx: Research Funding; Cyclacel: Research Funding; GSK: Research Funding; Jannsen: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding; PTC Therapeutics: Research Funding; FTC Therapeutics: Consultancy; Curio Science LLC: Consultancy; PTC Therapeutics: Consultancy; Argenx: Consultancy; Oncoceutics: Research Funding.

Download Full-text

Bcl-2 Protects against p53-Induced Apoptosis through Hdm2

Blood ◽

10.1182/blood.v112.11.5333.5333 ◽

2008 ◽

Vol 112 (11) ◽

pp. 5333-5333

Author(s):

Line Wergeland ◽

Kevin B. Spurgers ◽

Eystein Oveland ◽

Torill Høiby ◽

Manel Cascallo ◽

...

Keyword(s):

Dna Damage ◽

Acute Myeloid Leukemia ◽

Protein Level ◽

Myeloid Leukemia ◽

Proteasome Inhibitors ◽

Wild Type ◽

Inhibitory Molecule ◽

Wild Type P53 ◽

Induced Apoptosis ◽

Acute Myeloid

Abstract Hdm2 is up-regulated in several malignancies including sarcomas and acute myeloid leukemia, where it counteracts the anti-proliferative and pro-apoptotic effect of wild type p53. The anti-apoptotic protein Bcl-2 is often elevated in many tumors with wild type p53 and serves to block p53-induced apoptosis. We demonstrate that the protein level of Hdm2 positively correlates with the level of Bcl-2 and follows the Bcl-2 level in different cell systems. Over-expression of Bcl-2 protects Hdm2 from DNA-damage induced degradation in a dose dependant manner. In addition, modulation of Bcl-2 by shRNA knockdown reduced the Hdm2 protein level in parallel. Consequently, treatment of AML cells with the Bcl-2 small inhibitory molecule HA14-1 attenuated the level of Hdm2. The Bcl-2 level, but not the DNA damage induced Hdm2 degradation, was affected by disruption of the E3 ubiquitin ligase activity of Hdm2. In addition, the DNA-damage induced Hdm2 down-regulation was blocked by disrupted E1 ubiquitin-activation, defect polyubiquitination and by proteasome inhibitors. Finally, we show that Bcl-2 protection from p53-induced cell death requires co-expression of Hdm2 in double null p53/mdm2 mouse embryonic fibroblasts. Our results indicate that Bcl-2 regulates the Hdm2 level and that Hdm2 is a key mediator in Bcl-2 inhibition of p53-induced apoptosis. This is of particular therapeutic interest for cancers displaying elevated Hdm2 and Bcl-2, like sarcoma and acute myeloid leukemia.

Download Full-text

Stromal CYR61 Confers Resistance to Mitoxantrone Via Spleen Tyrosine Kinase Activation in Human Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v124.21.2228.2228 ◽

2014 ◽

Vol 124 (21) ◽

pp. 2228-2228

Author(s):

Xin Long ◽

Laszlo Perlaky ◽

Tsz-Kwong Chris Man ◽

Michele S. Redell

Keyword(s):

Bone Marrow ◽

Flow Cytometry ◽

Acute Myeloid Leukemia ◽

Cell Lines ◽

Stromal Cells ◽

Myeloid Leukemia ◽

Stromal Cell ◽

Chemotherapy Resistance ◽

Induced Apoptosis ◽

Acute Myeloid

Abstract Acute myeloid leukemia (AML) is a life-threatening bone marrow malignancy with a relapse rate near 50% in children, despite aggressive chemotherapy. Accumulating evidence shows that the bone marrow stromal environment protects a subset of leukemia cells and allows them to survive chemotherapy, eventually leading to recurrence. The factors that contribute to stroma-induced chemotherapy resistance are largely undetermined in AML. Our goal is to delineate the mechanisms underlying stroma-mediated chemotherapy resistance in human AML cells. We used two human bone marrow stromal cell lines, HS-5 and HS-27A, to study stroma-induced chemotherapy resistance. Both stromal cell lines are equally effective in protecting AML cell lines and primary samples from apoptosis induced by chemotherapy agents, including mitoxantrone, etoposide, and cytarabine. By gene expression profiling using the Affymetrix U133Plus 2 platform, we previously found that CYR61 was among the genes that were commonly upregulated in AML cells by both stromal cell lines. CYR61 is a secreted matricellular protein that is expressed at relatively low levels by AML cells, and at higher levels by stromal cells. CYR61 binds and activates integrins and enhances growth factor signaling in AML cells, and it has been associated with chemoresistance in other malignancies. Our current data provide functional evidence for a role for this protein in stroma-mediated chemoresistance in AML. First, we added anti-CYR61 neutralizing immunoglobulin (Ig), or control IgG, to AML-stromal co-cultures, treated with chemotherapy for 24 hours, and measured apoptosis with Annexin V staining and flow cytometry. In THP-1+HS-27A co-cultures treated with 50 nM mitoxantrone, the apoptosis rate was 33.0 ± 3.7% with anti-CYR61 Ig v. 16.3 ± 4.2% with control IgG; p=0.0015). Next, we knocked down CYR61 in the HS-5 and HS-27A stromal cell lines by lentiviral transduction of two individual shRNA constructs, and confirmed knockdown (KD) at the gene and protein levels for both cell lines. These CYR61-KD stromal cells provided significantly less protection for co-cultured AML cells treated with mitoxantrone, compared to stromal cells transduced with the non-silencing control. For example, the apoptosis rate for THP-1 cells co-cultured with CYR61-KD HS-27A cells was 10.8 ± 0.8%, compared to 6.8 ± 1.1% for THP-1 cells co-cultured with control HS-27A cells (p=0.02). Similar results were obtained with NB-4 AML cells. These results demonstrate that CYR61 contributes to stroma-mediated chemoresistance. CYR61 binds to integrin αvβ3 (Kireeva, et al, J. Biol. Chem., 1998, 273:3090), and this integrin activates spleen tyrosine kinase (Syk) (Miller, et al, Cancer Cell, 2013, 24:45). Using intracellular flow cytometry, we found that activated Syk (pSyk) increased in THP-1 and NB-4 cell lines, and in primary AML patient samples, upon exposure to control HS-27A cells. In primary samples, the mean fluorescence intensity (MFI) for pSyk averaged 11.7 ± 1.3 in co-culture v. 6.6 ± 0.6 for cells cultured alone (p=0.004, n=10). In contrast, pSyk did not significantly increase in AML cells co-cultured with CYR61-KD HS-27A cells (MFI for primary patient samples: 8.6 ± 0.8). This result implicates Syk as a downstream signaling mediator of CYR61. To determine the role of CYR61-induced Syk signaling in chemotherapy resistance, we treated AML-stromal cell co-cultures with 3 uM R406, a potent Syk inhibitor, or DMSO, then added 300 nM mitoxantrone, and measured apoptosis after 24 hours. In AML cells co-cultured with control HS-27A cells, mitoxantrone-induced apoptosis was significantly increased by Syk inhibition (THP-1 cells: 13.7 ± 0.7% with R406 v. 10.0 ± 0.3% with DMSO, p<0.05), consistent with reduced chemoresistance. Notably, R406 did not further increase mitoxantrone-induced apoptosis in AML cells co-cultured with CYR61-KD HS-27A stromal cells (THP-1 cells: 15.7 ± 0.2% with R406 v. 16.9 ± 0.4% with DMSO). Similar results were seen with NB-4 cells, as well. These results support the notion that CYR61 signals through the integrin-Syk pathway to protect AML cells from chemotherapy. Therefore, the CYR61 - integrin - Syk pathway may be a potential therapeutic target for overcoming stroma-induced chemotherapy resistance in AML. Disclosures No relevant conflicts of interest to declare.

Download Full-text

In vitro activity of a G-quadruplex-stabilizing small molecule that synergizes with Navitoclax to induce cytotoxicity in acute myeloid leukemia cells

BMC Cancer ◽

10.1186/s12885-019-6464-9 ◽

2019 ◽

Vol 19 (1) ◽

Cited By ~ 7

Author(s):

Justin J. Montoya ◽

Megan A. Turnidge ◽

Daniel H. Wai ◽

Apurvi R. Patel ◽

David W. Lee ◽

...

Keyword(s):

Dna Damage ◽

Acute Myeloid Leukemia ◽

Cell Lines ◽

Small Molecule ◽

Myeloid Leukemia ◽

In Vitro Activity ◽

Combination Drug ◽

G Quadruplex ◽

Acute Myeloid

Abstract Background Acute Myeloid Leukemia (AML) is a malignancy of myeloid precursor cells that arise from genomic alterations in the expression of key growth regulatory genes causing cells to assume an undifferentiated state and continue to proliferate. Recent efforts have focused on developing therapies that target specific protein products of aberrantly expressed genes. However, many of the identified proteins are difficult to target and thought to be “undrugable” because of structural challenges, protein overexpression, or mutations that confer resistance to therapy. A novel technology that circumvents some of these issues is the use of small molecules that stabilize secondary DNA structures present in the promoters of many potential oncogenes and modulate their transcription. Methods This study characterizes the in vitro activity of the G-quadruplex-stabilizing small molecule GQC-05 in AML cells. The effect of GQC-05 on three AML cell lines was analyzed using viability and apoptosis assays. GQC-05 has been shown to down-regulate MYC through G-quadruplex stabilization in Burkitt’s lymphoma cell lines. MYC expression was evaluated through qPCR and immunoblotting in the three AML cell lines following the treatment of GQC-05. In order to identify other therapeutic agents that potentiate the activity of GQC-05, combination drug screening was performed. The drug combinations were validated using in vitro cytotoxicity assays and compared to other commonly used chemotherapeutic agents. Results GQC-05 treatment of KG-1a, CMK and TF-1 cells decreased cell viability and resulted in increased DNA damage and apoptosis. Additionally, treatment of KG-1a, CMK and TF-1 with GQC-05 resulted in decreased expression of MYC mRNA and protein, with a more pronounced effect in KG-1a cells. Combination drug screening identified the Bcl-2/Bcl-XL inhibitor Navitoclax as a compound that potentiated GQC-05 activity. Co-treatment with GQC-05 and Navitoclax showed a synergistic decrease in cell viability of AML cells as determined by Chou-Talalay analysis, and induced more DNA damage, apoptosis, and rapid cytotoxicity. The cytotoxicity induced by GQC-05 and Navitoclax was more potent than that of Navitoclax combined with either cytarabine or doxorubicin. Conclusion These results suggest that the G-quadruplex stabilizing small molecule GQC-05 induces down regulated MYC expression and DNA damage in AML cells. Treatment with both GQC-05 with a Bcl-2/Bcl-XL inhibitor Navitoclax results in increased cytotoxic activity, which is more pronounced than Navitoclax or GQC-05 alone, and more significant than Navitoclax in combination with cytarabine and doxorubicin that are currently being used clinically.

Download Full-text

Evaluation of Poly(ADP-ribose) Polymerase Inhibitor, Pamiparib (BGB-290) in Treating Acute Myeloid Leukemia and the Characterization of Its Nanocarrier

Journal of Biomedical Nanotechnology ◽

10.1166/jbn.2021.3182 ◽

2021 ◽

Vol 17 (11) ◽

pp. 2165-2175

Author(s):

Xi Xu ◽

Jian Wang ◽

Tong Tong ◽

Shao-Fen Lin ◽

Congmin Liu ◽

...

Keyword(s):

Dna Damage ◽

Acute Myeloid Leukemia ◽

Cell Lines ◽

Myeloid Leukemia ◽

Parp Inhibitor ◽

Chemotherapy Resistance ◽

Disease Free Survival ◽

Plga Nanoparticles ◽

Leukemia Treatment ◽

Acute Myeloid

Despite the continuous improvement of leukemia treatment in the clinic, the overall 5-year disease-free survival of acute myeloid leukemia (AML) is only approximately 30%–60% due to relapse and the refractoriness of AML after traditional chemotherapy. Inhibition of poly(ADP-ribose) polymerase (PARP), a member of the DNA damage repair complex, has a strong antitumor effect in solid tumors. However, the role of PARP in AML remains unclear. We found that high levels of PARP1 and PARP2 were positively related to chemotherapy resistance and poor prognosis in patients with AML. Doxorubicin (DOX)-resistant AML cells highly expressed PAPR1 and PARP2. Knockdown of PARP1 and PARP2, or pharmaceutical inhibition of PARP by the PARP inhibitor (PARPi) BGB-290, significantly enhanced the cytotoxicity of DOX in AML cells due to increased DNA damage. PLGA-loading BGB-290 was properly self-assembled into stable BGB-290@PLGA nanoparticles (NPs), which is uniform particle size and good stability. BGB-290@PLGA is easily uptake by AML cell lines and stays for a long time. Combined with DOX, BGB-290@PLGA can significantly improve the chemosensitivity of AML cell lines. Furthermore, BGB-290 and DOX combination treatment dramatically repressed the onset of leukemia and prolonged the survival of THP-1 xenografted mice. Overall, this study demonstrated that PARPi with traditional chemotherapy could be an efficient therapeutic strategy for AML.

Download Full-text

Autophagy Inhibition Enhances CDK4/6 Inhibitor-Induced Apoptosis in t(8;21) Acute Myeloid Leukemia Cells

Blood ◽

10.1182/blood-2020-133881 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 50-50

Author(s):

Kana Nakatani ◽

Hidemasa Matsuo ◽

Yutarou Harata ◽

Moe Higashitani ◽

Asami Koyama ◽

...

Keyword(s):

Cell Cycle ◽

Cell Proliferation ◽

Cell Lines ◽

Myeloid Leukemia ◽

G1 Phase ◽

Therapeutic Approaches ◽

Cycle Arrest ◽

Induced Apoptosis ◽

Autophagy Inhibition ◽

Acute Myeloid

Acute myeloid leukemia (AML) is a genetically and clinically heterogeneous disease. Although t(8;21) AML patients have a more favorable prognosis than other cytogenetic subgroups, nearly 40% of t(8;21) AML patients experience relapse. Therefore, novel therapeutic approaches based on a better understanding of the biology of t(8;21) AML need to be developed. In this study, at first, we re-analyzed the sequencing data of 149 pediatric t(8;21) AML patients from St. Jude Children's Research Hospital tissue resource core facility and the JPLSG AML-05 study, and 134 adult t(8;21) AML patients from CALGB/Alliance trials and the University Hospital of Ulm. In pediatric patients, 13 CCND2 mutations were detected in 11 patients (11/149, 7.4%), and in adult patients, 14 CCND2 mutations were detected in 12 patients (12/134, 9.0%). In both cohorts, CCND2 mutations were located on the PEST domain, suggesting that the mutations stabilize the cyclin D2 protein. Next, we compared CCND2 mRNA expression between t(8;21) AML patients (n=24) and non-t(8;21) AML patients (n=163) using the TARGET AML cohort. In non-t(8;21) AML patients, CCND2 expression varied from low to high levels, whereas in t(8;21) AML patients, CCND2 expression was restricted to higher levels. Consistently, CCND2 expression was higher in t(8;21) AML cell lines (n=2: Kasumi-1 and SKNO-1), compared with non-t(8;21) AML cell lines (n=32). Kasumi-1 cells transfected with shCCND2 showed cell cycle arrest at G1 phase and impaired cell proliferation. These results suggest that the frequency of CCND2 mutations and CCND2 expression are increased in t(8;21) AML, and high CCND2 expression plays an important role in t(8;21) AML cell proliferation. Because CCND2 is not a druggable target, we examined the effect of CDK4/6 inhibitors (palbociclib and abemaciclib) on t(8;21) AML cells. Analysis of 19 AML cell lines showed that t(8;21) AML cells had lower IC50 values for CDK4/6 inhibitors than non-t(8;21) AML cells. CDK4/6 inhibitors caused cell cycle arrest at G1 phase and impaired cell proliferation in t(8;21) AML cells. To identify potential therapeutic approaches in combination with CDK4/6 inhibitors in t(8;21) AML, we performed microarray analysis and examined the effects of CDK4/6 inhibition. In addition to the pathways associated with the cell cycle (regulation of sister chromatid separation, retinoblastoma gene, and cell cycle), the MAP-ERK and PI3K-AKT-mTOR signaling pathways were downregulated by CDK4/6 inhibition. Because these pathways are involved in autophagy regulation via mTOR, we focused on examining autophagy in subsequent experiments. Assessment of the effect of CDK4/6 inhibition on autophagy in t(8;21) AML cells showed that the CDK4/6 inhibitor (abemaciclib) treatment induced LC3B-I to LC3B-II conversion in both Kasumi-1 and SKNO-1 cells. Transmission electron microscopic examination of autophagosome formation detected a large number of autophagosomes in the cytoplasm of Kasumi-1 and SKNO-1 cells treated with abemaciclib, whereas few autophagosomes were detected in control samples. These results suggest that autophagy is induced by CDK4/6 inhibition in t(8;21) AML cells. Autophagy is involved in the resistance to chemotherapy in cancer cells, therefore, we hypothesized that autophagy inhibition may be a promising therapeutic approach. Treatment of t(8;21) AML cells with the autophagy inhibitors chloroquine (CQ) or LY294002 in combination with abemaciclib significantly increased the frequency of apoptotic (Annexin V positive) cells compared with that in untreated cells, whereas CQ or LY294002 single treatment had no significant effect on apoptosis. Consistently, combinatorial inhibition of CDK4/6 and autophagy upregulated cleaved caspase 3 expression. The combinatorial effect was confirmed by silencing the autophagy-related protein ATG7 using small interfering RNA in abemaciclib-treated t(8;21) AML cells. These results suggest that autophagy inhibition enhances CDK4/6 inhibitor-induced apoptosis in t(8;21) AML cells. In conclusion, the present results indicate that inhibition of CDK4/6 and autophagy may be a novel and promising biomarker-driven therapeutic strategy for the treatment of t(8;21) AML. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Inhibition of Histone Deacetylases 1 and 6 Enhances Ara-C-Induced Apoptosis In Pediatric Acute Myeloid Leukemia Cells

Blood ◽

10.1182/blood.v116.21.3275.3275 ◽

2010 ◽

Vol 116 (21) ◽

pp. 3275-3275

Author(s):

Xuelian Xu ◽

Chengzhi Xie ◽

Holly Edwards ◽

Hui Zhou ◽

Steven Buck ◽

...

Keyword(s):

Clinical Trials ◽

Acute Myeloid Leukemia ◽

Cell Lines ◽

Myeloid Leukemia ◽

Class I ◽

Pediatric Aml ◽

Induced Apoptosis ◽

Class I Hdacs ◽

The Impact ◽

Acute Myeloid

Abstract Abstract 3275 Acute myeloid leukemia (AML) accounts for one-fourth of acute leukemias in children, but is responsible for more than half of the leukemia deaths in this patient population. Resistance to cytarabine (ara-C)-based chemotherapy is a major cause of treatment failure in this disease. Therefore, new therapies for children with AML are urgently needed. Among the newer agents that have been recently investigated in high-risk AML in adults, histone deacetylase (HDAC) inhibitors [HDACIs, e.g., valproic acid (VPA) and Vorinostat (SAHA)] are particularly notable. The ability of HDACIs to induce cell differentiation, cell cycle arrest, and apoptosis in human leukemic cells, but not in normal cells, has stimulated significant interest in their potential as anti-leukemia agents. Numerous HDACIs have been developed during the last decade and the majority of these are in clinical trials including the novel class I-selective HDACIs, MS-275 and MGCD0103, and pan-HDACIs, LBH-589 and PXD101. Despite the well-characterized molecular and cellular effects of HDACIs, single-agent activity for this class of drugs has been modest. However, the clinical usefulness of HDACIs may be increased through rationally designed combination strategies including HDACIs with standard chemotherapy drugs. We previously hypothesized that VPA synergizes with ara-C, resulting in enhanced antileukemic activity in pediatric AML, by inducing apoptosis. We examined the impact of VPA on ara-C cytotoxicities in a panel of pediatric AML cell lines and diagnostic blast samples from children with de novo AML and demonstrated highly synergistic antileukemic activities of combined ara-C and VPA. This was especially pronounced in samples with t(8;21). Our mechanistic studies revealed that induction of DNA damage and Bim underlay the synergistic antileukemic activities of this drug combination. The present study was designed to identify members of the HDAC family which were deteminants of ara-C sensitivities, and to select the optimal HDACIs that were most efficacious when combined with ara-C for treating AML. Expression profiles of HDACs 1–11 in 4 clinically relevant pediatric AML cell lines (THP-1, Kasumi-1, MV4-11, and CMS) suggested that HDACs 5 and 11 were likely not involved due to marginal or lack of expression. The remaining class II HDACs and the entire class I enzymes could be relevant to HDACI anti-leukemic activities, based on the relationships between HDAC levels and HDACI cytotoxicities and responses to the combined VPA and ara-C, although the impact of class I HDACs seemed to predominate. Treatment of THP-1 cells with structurally-diverse HDACIs [SAHA (a pan-HDACI), VPA (a relatively class I selective-HDACI), and MS-275 (a class I selective-HDACI)] and enzymatic assays following immunoprecipitation of class I HDACs, revealed that inhibition of class I HDACs could augment ara-C-induced apoptosis. However, class II HDACs (e.g., HDAC6) were also implicated since SAHA was also effective. shRNA knockdown of HDACs 1 or 6 resulted in ∼2-fold increased apoptosis induced by ara-C in THP-1 AML cells (p<0.05). This was accompanied by substantially increased expression of Bim (2.3- and 1.4-fold, respectively). Down-regulation of HDAC2 resulted in ∼30% decreased ara-C-induced apoptosis. In contrast, shRNA knockdown of HDACs 3 and 4 had no effects on ara-C-induced apoptosis in THP-1 cells. At clinically achievable concentrations, HDACIs that simultaneously inhibited both HDACs 1 and 6 showed the best anti-leukemic activities and significantly enhanced ara-C-induced apoptosis in pediatric AML sublines including THP-1 and Kasumi-1. Our results further establish that HDACs are promising therapeutic targets for treating pediatric AML and identified HDACs 1 and 6 as the most relevant drug targets. Accordingly, treating pediatric AML patients with pan-HDACIs may be more beneficial than HDAC isoform-specific drugs. Based on our results, incorporation of pan-HDACIs (e.g., LBH-589 and PXD101) into ara-C-based clinical trials for treating pediatric AML should be strongly considered. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

Small Molecule Inhibition of SIRT Activity: A Novel Therapeutic Approach for Acute Myeloid Leukemia

Blood ◽

10.1182/blood.v118.21.84.84 ◽

2011 ◽

Vol 118 (21) ◽

pp. 84-84

Author(s):

Steffan T Nawrocki ◽

Claudia M Espitia ◽

Kevin R. Kelly ◽

William G. Bornmann ◽

Jennifer S Carew

Keyword(s):

Acute Myeloid Leukemia ◽

Cell Lines ◽

Small Molecule ◽

Myeloid Leukemia ◽

Conflicts Of Interest ◽

Clonogenic Survival ◽

Altered Gene ◽

Induced Apoptosis ◽

Acute Myeloid ◽

Novel Therapeutic

Abstract Abstract 84 New therapeutic strategies are urgently needed to improve clinical outcomes for patients with acute myeloid leukemia (AML), which is an extremely aggressive disease with very few long-term survivors. The sirtuin deacetylases (SIRTs) are critical regulators of genes that are essential for longevity, cell growth, tumor suppression, and apoptosis. Elevated SIRT expression has been reported in several types of cancer and may promote pathogenesis and drug resistance by increasing the lifespan and survival capacity of malignant cells. Our preliminary analysis of SIRT expression indicated that SIRT1 was consistently expressed at significantly higher levels in AML cell lines and primary AML blasts as compared with normal controls. In order to investigate the potential role of SIRT1 as a regulator of AML pathogenesis, we utilized shRNA to stably knockdown its expression in MV4-11 and KG-1 AML cells. Cells with targeted SIRT1 knockdown displayed an altered gene expression profile as compared with non-targeted controls. Moreover, antagonizing SIRT1 expression significantly impeded the progression of AML in a xenograft mouse model. A number of deacetylase inhibitors have been clinically evaluated for cancer therapy. However, disrupting SIRT function as an anticancer strategy remains to be rigorously investigated as none of these previously studied drugs significantly inhibit the activity of this class of NAD+-dependent deacteylases. Tenovin-6 is a novel small molecule SIRT inhibitor. We investigated the efficacy and pharmacodynamic effects of tenovin-6 in AML cell lines, primary blasts from patients with AML, and mouse models. Treatment with tenovin-6 induced apoptosis and dramatically diminished AML clonogenic survival. Tenovin-6 promoted a dose-dependent increase in the acetylated levels of the SIRT-regulated gene p53 in AML cells and triggered the induction of several p53 transcriptional targets including p21 and PUMA. Targeted knockdown of PUMA with shRNA significantly reduced the pro-apoptotic effects of tenovin-6, indicating that it is a critical mediator of its anti-leukemic activity. Notably, administration of tenovin-6 to mice implanted with AML cells was well-tolerated and led to a highly significant reduction in disease burden and increase in overall survival. Our collective findings demonstrate that SIRT1 is a promising novel therapeutic target in AML. Further investigation aimed to elucidate the safety, efficacy, and mechanism of action of tenovin-6 is warranted. Disclosures: No relevant conflicts of interest to declare.

Download Full-text