Proliferation Of Acute Myeloid Leukemia Cell Lines Research Articles

Addiction to Small Gtpase ARF6-Mediated Sphingolipid Homeostasis By AML but Not the Host

Background Cancer cells' unique metabolic demand has emerged as a promising therapeutic target in Acute Myeloid Leukemia (AML). The vesicular trafficking and signaling gatekeeper, ADP-Ribosylation Factor 6 (ARF6), belongs to the RAS superfamily of small GTPases and has been shown to regulate the homeostasis of lipids such as PIP2, phosphatidic acids, and cholesterol. Here we describe AML cells' unusual addiction to ARF6-mediated sphingolipid homeostasis and its clinical significance. Experiments and Results ARF6 knockdown (KD) or CRISPR-mediated ARF6 knockout (KO) inhibited the proliferation of AML cell lines, THP-1 and MV4-11, as well as the colony formation of primary AML CD34 + cells. Surprisingly, Tamoxifen-induced whole body KO of Arf6 in adult Arf6 f/f;Rosa-CreERT 2 mice led to healthy and grossly normal mice with a normal lifespan. Adult mice lacking ARF6 show no abnormality in complete blood count, urine test, or histology. Hence, ARF6 is genetically indispensable for AML, but not for the host. To confirm AML's addition to ARF6 in vivo, we introduced Arf6 KO in an MLL-AF9-induced AML model in C57BL6/J mice. We are currently following up with the disease progression between Arf6-KO AML group and control AML group, and expect to obtain results before the 2023 ASH meeting. After discovering that ARF6 is genetically necessary for AML but not needed for the host, we analyzed its clinical significance. Since ARF6 mutations are not detected in AML samples, we focused on analyzing its expression. With univariate analysis, we show that high ARF6 expression (top 50%) is significantly associated with worse overall survival (OS) and worse disease-free survival (DFS) of AML patients in the TCGA-NEJM-2013 (TCGA) cohort (N=200) and the Münchner Leukämielabor (MLL) cohort (N=579). In multi-variate analysis, high ARF6 expression is significantly associated with worse OS in the BeatAML cohort (N=562) and shows a trend towards worse OS and DFS in the TCGA cohort. Following a hypothesis-driven approach, we investigated the role of ARF6 in regulating sphingolipid homeostasis by HPLC-MS lipidomic analyses of AML cells (THP-1) with or without ARF6 depletion. Lipidomic profiles revealed that ARF6 KD led to an increase of the overall ceramide/sphingomyelin ratio, suggesting a defect in sphingolipid homeostasis. We then analyzed the expression of sphingolipid metabolic enzymes and observed that ARF6 KD downregulated sphingomyelin synthase 1 and 2 (SGMS1 and SGMS2) expression, hindering ceramide-to-sphingomyelin conversion. Supporting this, we found a positive linear correlation between ARF6 and SGMS1/2 expression among the patients in TCGA cohort, confirming their correlation. High expression of the ARF6 effectors SGMS1/2 is also associated with worse OS and DFS in the TCGA cohort and the MLL cohort in univariate analysis, resembling that of ARF6. Downstream of ceramide accumulation, ARF6 KD inhibited the pro-survival AKT pathway, confirming the pro-apoptotic roles of ceramide in cancers. The anti-proliferative effect of ARF6 depletion can be rescued by sphingomyelinase inhibitor GW4869 (blocking ceramide production) or by expressing a constitutively active form of AKT (AKT1 E17K). To pharmacologically target ARF6, we developed two generations of ARF6 small molecular inhibitor pro-drugs, named NAV-2729 and A6-4471. NAV-2729 and A6-4471 showed high specificity to ARF6 without inhibiting other small GTPases, with in vitro IC 50 in the lower μM range. Both NAV-2729 and A6-4471 inhibited AML cell line proliferation and reduced primary AML cell colony formation in lower μM range. Cord blood normal CD34 + cells are not sensitive to ARF6 inhibitors, but non-specific toxicity was observed at higher concentrations. When tested in vivo with THP-1 xenografts in NSG mice, both inhibitors reduced circulating AML cells without obvious toxicity to the host. Conclusion ARF6 is necessary for AML proliferation and its higher expression is associated with worse patient survival. However, ARF6 is dispensable for normal host physiology. Mechanistically, ARF6 maintains critical ceramide/sphingomyelin balance in AML by regulating SGMS1/2 expression. Pharmacologically inhibiting ARF6 suppressed AML proliferation in vitro and in vivo in a genotype-agnostic fashion. Our study implicates ARF6 as a potentially actionable and safe target in AML.

Targeting Epigenetic Resistance Mechanisms to PI3 Kinase Inhibition in Leukemic Stem Cells

Acute myeloid leukemia (AML) is a heterogeneous disease associated with poor survival and frequent relapse rates due to the inability to effectively target leukemic stem cells (LSCs) and acquired resistance to existing treatments. Development of treatments targeting LSCs and overcoming acquired resistance is crucial to improve the survival of AML patients. The PI3 kinase (PI3K)/AKT signaling pathway is activated in 80% of AML patients, across various AML subtypes, making PI3K an attractive therapeutic target for this disease. Several PI3K inhibitors, such as copanlisib, are clinically approved for other indications, with a reasonable toxicity profile. The effects of PI3K inhibitors on LSCs however, remains unknown. Several catalytic isoforms of PI3K are expressed in hematopoietic cells. To determine whether these PI3K isoforms play a role in LSC self-renewal, we performed colony assays on KMT2A-AF9 retrovirally transduced hematopoietic stem and progenitor cells (HSPCs) with either genetic deletion or pharmacologic inhibition of PI3K isoforms. We found that disruption of PI3K signaling reduces the self-renewal of LSCs and promotes myeloid differentiation in both mouse LSCs and human AML cell lines. KMT2A-AF9 induces leukemic transformation via aberrant upregulation of key self-renewal genes in hematopoietic progenitors, such as HoxA9 and Meis1 (PMID: 16862118). We found that pharmacologic inhibition of PI3K isoforms leads to a reduction in HoxA9 and Meis1 expression in LSC colonies. In the KMT2A-AF9 retroviral bone marrow transplantation model of AML, genetic deletion of the PI3K isoform Pik3ca leads to a reduction in LSC numbers in the bone marrow and prolonged survival (Fig 1A), although it is not curative. In addition, we observed significant prolongation of survival upon secondary transplantation of Pik3ca leukemic cells, suggesting a reduction in functional LSCs. Transcriptome analysis on LSCs isolated from pre-clinical bone marrow aspirates of KMT2A-AF9 primary transplant mice revealed downregulation of the target genes of HoxA9, an important driver of LSC self-renewal. We also observed enrichment of the targets of EZH2, a histone methyltransferase that catalyzes the H3K27 trimethylation repressive mark. AKT is known to phosphorylate EZH2 at Ser21, leading to inhibition of EZH2 function (PMID: 16224021). Therefore, we hypothesized that Pik3ca deletion can promote LSC differentiation by de-repressing EZH2 activation via AKT inactivation. To determine whether PI3K inactivation differentiates KMT2A-AF9 leukemic cells via dephosphorylation of EZH2, we performed Western blot analysis on bone marrow cells from Pik3ca KO and WT leukemic mice. As expected, Pik3ca deletion significantly reduced AKT phosphorylation. Unexpectedly, a reduction of total EZH2 protein levels was also observed in Pik3ca KO leukemic cells (Fig 1B), suggesting that EZH2 downregulation may be a non-genetic acquired resistance mechanism to PI3K inactivation. Histone proteomics analysis at two different timepoints after treatment with the PI3K inhibitor copanlisib revealed rapid and dynamic changes in histone modifications, including H3K27me3 and H3K4me3, consistent with epigenetic mechanisms of resistance to PI3K inhibition. EZH1, a homolog of EZH2, has been reported to compensate for EZH2 function (PMID: 26219303, PMID: 31189531). Thus, we hypothesize that PI3K inhibition may sensitize leukemic cells to EZH1/2 dual inhibition by reducing EZH2 levels. We found that dual inhibition with copanlisib and the EZH1/2 inhibitor valemetostat leads to a combinatorial effect to strongly decrease the proliferation of AML cell lines and AML patient samples. Additionally, we found that treatment of KMT2A-AF9 AML mice with these compounds induces myeloid differentiation and leads to a reduction in leukemia initiating cell capacity, as demonstrated by prolonged survival upon secondary transplantation. Overall, our data suggests that PI3K plays an important role in leukemic stem cells, and that EZH2 downregulation is a non-genetic mechanism of resistance to PI3K inhibition. Additionally, our findings indicate that combining PI3K inhibitors with EZH1/2 dual inhibitors could be a promising therapeutic approach to reduce LSCs, prevent resistance, and prolong survival in AML patients.

Allosteric SHP2 inhibition increases apoptotic dependency on BCL2 and synergizes with venetoclax in FLT3- and KIT-mutant AML

Mutations in the receptor tyrosine kinases (RTKs) FLT3 and KIT are frequent and associated with poor outcomes in acute myeloid leukemia (AML). Although selective FLT3 inhibitors (FLT3i) are clinically effective, remissions are short-lived due to secondary resistance characterized by acquired mutations constitutively activating the RAS/MAPK pathway. Hereby, we report the pre-clinical efficacy of co-targeting SHP2, a critical node in MAPK signaling, and BCL2 in RTK-driven AML. The allosteric SHP2 inhibitor RMC-4550 suppresses proliferation of AML cell lines with FLT3 and KIT mutations, including cell lines with acquired resistance to FLT3i. We demonstrate that pharmacologic SHP2 inhibition unveils an Achilles' heel of RTK-driven AML, increasing apoptotic dependency on BCL2 via MAPK-dependent mechanisms, including upregulation of BMF and downregulation of MCL1. Consequently, RMC-4550 and venetoclax are synergistically lethal in AML cell lines and in clinically relevant xenograft models. Our results provide mechanistic rationale and pre-clinical evidence for co-targeting SHP2 and BCL2 in RTK-driven AML.

Gene SH3BGRL3 regulates acute myeloid leukemia progression through circRNA_0010984 based on competitive endogenous RNA mechanism.

Introduction: Acute myeloid leukemia (AML) is a malignant proliferative disease affecting the bone marrow hematopoietic system and has a poor long-term outcome. Exploring genes that affect the malignant proliferation of AML cells can facilitate the accurate diagnosis and treatment of AML. Studies have confirmed that circular RNA (circRNA) is positively correlated with its linear gene expression. Therefore, by exploring the effect of SH3BGRL3 on the malignant proliferation of leukemia, we further studied the role of circRNA produced by its exon cyclization in the occurrence and development of tumors. Methods: Genes with protein-coding function obtained from the TCGA database. we detected the expression of SH3BGRL3 and circRNA_0010984 by real-time quantitative polymerase chain reaction (qRT-PCR). We synthesized plasmid vectors and carried out cell experiments, including cell proliferation, cell cycle and cell differentiation by cell transfection. We also studied the transfection plasmid vector (PLVX-SHRNA2-PURO) combined with a drug (daunorubicin) to observe the therapeutic effect. The miR-375 binding site of circRNA_0010984 was queried using the circinteractome databases, and the relationship was validated by RNA immunoprecipitation and Dual-luciferase reporter assay. Finally, a protein-protein interaction network was constructed with a STRING database. GO and KEGG functional enrichment identified mRNA-related functions and signaling pathways regulated by miR-375. Results: We identified the related gene SH3BGRL3 in AML and explored the circRNA_0010984 produced by its cyclization. It has a certain effect on the disease progression. In addition, we verified the function of circRNA_0010984. We found that circSH3BGRL3 knockdown specifically inhibited the proliferation of AML cell lines and blocked the cell cycle. We then discussed the related molecular biological mechanisms. CircSH3BGRL3 acts as an endogenous sponge for miR-375 to isolate miR-375 and inhibits its activity, increases the expression of its target YAP1, and ultimately activates the Hippo signaling pathway involved in malignant tumor proliferation. Discussion: We found that SH3BGRL3 and circRNA_0010984 are important to AML. circRNA_0010984 was significantly up-regulated in AML and promoted cell proliferation by regulating miR-375 through molecular sponge action.

Phase 1B/2A safety, pharmacokinetics and pharmacodynamics study of fosciclopirox alone and in combination with cytarabine in patients with relapsed/refractory acute myeloid leukemia.

TPS7078 Background: Fosciclopirox (CPX-POM) is a broad-spectrum anticancer agent being developed through a public-private partnership between CicloMed LLC and KU Cancer Center (KUCC). Following intravenous administration, fosciclopirox is rapidly and completely metabolized to its active metabolite ciclopirox (CPX). Given fosciclopirox is a prodrug lacking pharmacologic activity, in vitro mechanistic studies were conducted utilizing CPX as the test article. In collaboration with Notable Labs (Foster City CA), we characterized ex vivo sensitivity to CPX in bone marrow and peripheral blood samples from ten newly diagnosed and relapsed acute myeloid leukemia (AML) patients. Reductions in blast counts were seen in each of the 10 patients studied at clinically relevant concentrations. In vitro experiments in AML cell lines (HL-60 and MV4-11) characterized the mechanism(s) of the anti-leukemia activity of CPX. CPX inhibited proliferation of AML cell lines in a dose- and time-dependent manner with IC50 values ranging from 2.5-4 µM. CPX induced cell cycle arrest in the subG0 phase and CPX-treated cells lost their ability to enter to G0-G1 phase. Moreover, CPX induced early and late phase apoptosis. CPX also activated Caspase 3/7 activity. This preclinical data led to the development of a multi-center Phase 1B/2A clinical proof of concept trial (NCT04956042) in AML patients. Methods: Eligible AML patients are adults with primary refractory (two prior regimens) or relapsed AML; ECOG PS 0-2; adequate end organ function. Prior allogeneic stem cell transplant is allowed if patient is more than 100 days post-transplant with no active graft-versus-host disease. CPX-POM is administered as 900 mg/m2 once daily as an IV infusion on Days 1 to 5 of each 21-day cycle. Day 8 bone marrow sample is collected for correlative studies. Ex vivo Drug Sensitivity Screening (DSS) will be performed on samples obtained prior to treatment and C1 Days 8 and 21. 14 evaluable patients will be enrolled in Cohort 1a. If disease response is observed in at least 4 of 14 patients, an additional 14 patients will be enrolled in Cohort 1b. During Cohort 1a, patients who do not respond to CPX-POM alone may be switched to the combination of CPX-POM + cytarabine. Patients who respond to the combination treatment may continue until evidence of disease progression. If disease response to CPX-POM alone is not observed in at least 4 of 14 patients in Cohort 1a, the study may be terminated or a Cohort 2a may be initiated using the combination of CPX-POM and cytarabine. The trial is currently open at two sites with 14 patients enrolled and 8 evaluable for the primary endpoint. Clinical trial information: NCT04956042 .

Aging-related genes related to the prognosis and the immune microenvironment of acute myeloid leukemia.

Acute myeloid leukemia (AML), one of the common malignancies of the hematologic system, has progressively increased in incidence. Aging is present in both normal tissues and the tumor microenvironment. However, the relationship between senescence and AML prognosis is still not elucidated. In this study, RNA sequencing data of AML were obtained from TCGA, and prognostic prediction models were established by LASSO-Cox analysis. Differences in immune infiltration between the different risk groups were calculated using the CIBERSORT and ESTIMATE scoring methods. The KEGG and GO gene enrichment and GSEA enrichment were also used to enrich for differential pathways between the two groups. Subsequently, this study collected bone marrow samples from patients and healthy individuals to verify the differential expression of uncoupling protein 2 (UCP2) in different populations. Genipin, a UCP2 protein inhibitor, was also used to examine its effects on proliferation, cell cycle, and apoptosis in AML cell lines in vitro. It showed that aging-related genes (ARGs) expression was correlated with prognosis. And there was a significant difference in the abundance of immune microenvironment cells between the two groups of patients at high risk and low risk. Subsequently, UCP2 expression was found to be elevated in AML patients. Genipin inhibits UCP2 protein and suppresses the proliferation of AML cell lines in vitro. ARGs can be used as a predictor of prognosis in AML patients. Moreover, suppressing UCP2 can reduce the proliferation of AML cell lines, alter their cell cycle, and promote apoptosis in vitro.

Combination of the Kdm-Family Inhibitor, Jib-04, Improves Response to Acute Myeloid Leukemia Cells to Venetoclax

Background: Acute Myeloid Leukemia (AML) is a heterogeneous hematological malignancy with a 5-year survival rate of about 30% in adults with AML. While over the prior several decades, the standard of care treatment for AML changed very little, a number of novel targeted therapies have emerged in recent years. Promising results from clinical trials with the BCL2-specific inhibitor, Venetoclax, in combination with hypomethylating agents (HMA) or low-dose cytarabine for AML treatment have generated enthusiasm in the field. However, data from a phase II trial indicated a 30% failure rate after Venetoclax+HMA treatment of newly diagnosed patients, suggesting additional options are needed. Thus, we sought to explore alternative drug combinations that may enhance the efficacy of Venetoclax. JIB-04 is a potent small molecule inhibitor of multiple members of the histone lysine demethylase (KDM) 4, 5 and 6 families with KDM5A being the most sensitive. Expression levels of histone lysine-specific demethylases are higher in AML compared to normal bone marrow, suggesting they are potential targets for therapeutic intervention. Pharmacological inhibition or genetic knock down of KDM 4, 5 and 6 family members leads to reduced proliferation, cell cycle arrest, and increased apoptosis of AML cells of various subtypes. These preliminary findings compelled us to explore the anti-leukemic activity of JIB-04 alone and in combination with Venetoclax. Methods: We treated AML cell lines, patient AML blasts, and CD34+ cells from healthy donors with JIB-04, Venetoclax, or the combination for 72 hours in vitro. Apoptosis was quantified by AnnexinV/propidium iodide (PI) staining. Cell proliferation of AML cell lines treated with JIB-04 was evaluated using MTT assay and transcriptome profiling was done by RNA-Seq. NSG mice were injected with MOLM-13 cells and treated with JIB-04, Venetoclax or the combination for two weeks. For the knock-down (KD) of DDIT4 MOLM-13 cells were transduced with a shRNA and cells were treated with Venetoclax for 72h and analyzed for apoptosis. Results: Treatment of AML cell lines with low nanomolar doses (IC50 range from 8-60nM) of JIB-04 resulted in inhibition of proliferation and induction of apoptosis. In all AML cell lines tested, including AML cell lines with relative resistance to Venetoclax, the combination of JIB-04 with Venetoclax showed a strong synergistic effect. Moreover, patient AML blasts also showed a synergistic response to the drug combination compared to single-drug treatments (Figure 1a). In contrast, viability of normal CD34+ hematopoietic cells was not affected by JIB-04 treatment even up to a dose of 100nM that leads to apoptosis in AML cells, indicating a broad therapeutic window. The combination treatment of NSG mice injected with MOLM-13 cells resulted in reduced engraftment of huCD45+ cells compared to the single treatments in the blood, bone marrow and spleen. RNA sequencing of AML-OCI3 and MOLM-13 cells treated with JIB-04 revealed regulation of genes related to the mTOR pathway, stress response or amino acid metabolism, indicating possible mechanisms affecting proliferation and apoptosis. DDIT4 (REDD1), a regulator of the mTOR pathway, was downregulated after JIB-04 treatment in both cell lines. KD of DDIT4 in MOLM-13 cells resulted in increased sensitivity to Venetoclax (Figure 1b). Summary/Conclusion: While the epigenetic inhibitor JIB-04 alone shows modest anti-leukemic effect, this study highlights the potential therapeutic benefit of combining JIB-04 and Venetoclax in AML. The analysis of transcriptomic changes after JIB-04 treatment identified the mTOR pathway regulator DDIT4 as a likely mediator of the sensitization of AML cells to Venetoclax. High DDIT4 expression is associated with a worse outcome in AML making it an attractive therapeutic target for AML, especially in combination with Venetoclax. Our result would suggest this drug combination as a possible treatment option for AML patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

MK256 is a novel CDK8 inhibitor with potent antitumor activity in AML through downregulation of the STAT pathway.

Acute myeloid leukemia (AML) is the most lethal form of AML due to disease relapse. Cyclin dependent kinase 8 (CDK8) is a serine/threonine kinase that belongs to the family of Cyclin-dependent kinases and is an emerging target for the treatment of AML. MK256, a potent, selective, and orally available CDK8 inhibitor was developed to target AML. We sought to examine the anticancer effect of MK256 on AML. In CD34+/CD38- leukemia stem cells, we found that MK256 induced differentiation and maturation. Treatment of MK256 inhibited proliferation of AML cell lines. Further studies of the inhibitory effect suggested that MK256 not only downregulated phosphorylated STAT1(S727) and STAT5(S726), but also lowered mRNA expressions of MCL-1 and CCL2 in AML cell lines. Efficacy of MK256 was shown in MOLM-14 xenograft models, and the inhibitory effect on phosphorylated STAT1(S727) and STAT5(S726) with treatment of MK256 was observed <i>in vivo</i>. Pharmacologic dynamics study of MK256 in MOLM-14 xenograft models showed dose-dependent inhibition of the STAT pathway. Both <i>in vitro</i> and <i>in vivo</i> studies suggested that MK256 could effectively downregulate the STAT pathway. <i>In vitro</i> ADME, pharmacological kinetics, and toxicity of MK256 were profiled to evaluate the drug properties of MK256. Our results show that MK256 is a novel CDK8 inhibitor with a desirable efficacy and safety profile and has great potential to be a promising drug candidate for AML through regulating the STAT pathway.

RSK Inhibition Induces Apoptosis by Downregulating Protein Synthesis in a Variety of Acute Myeloid Leukemia Cell Lines.

Fms-like tyrosine kinase 3 (FLT3) and isocitrate dehydrogenase 1/2 (IDH1/2) mutations drive malignancy in acute myeloid leukemia (AML), which accounts for approximately 40% of AML cases. Treatment with FLT3 or IDH1/2 inhibitors is used for such patients; however, it is not considered for most patients with AML who lack mutations on the respective genes. In this study, p90 ribosomal S6 kinase (RSK) was found to serve as a new therapeutic target in various AMLs with or without FLT3 mutations. BI-D1870, a potent inhibitor of RSK, significantly suppressed the proliferation of AML cell lines, among which three encoded wild-type FLT3 and three contained FLT3 driver mutations, compared with chronic myeloid leukemia K562 cells or other adherent cancer cells. BI-D1870 inhibited protein synthesis by dephosphorylating the p70 S6 kinase and eukaryotic initiation factor 4E-binding protein 1 in all AML cells except KG-1a cells. Meanwhile, the expression of microtubule-associated protein light chain 3B-I and -II increased in KG-1a cells treated with BI-D1870. BI-D1870 induced caspase-dependent apoptosis in all AML cells, including KG-1a cells. We next investigated the synergistic effect of BI-D1870 with cytarabine, a traditional anticancer drug used in AML. Synergistic effects of BI-D1870 and cytarabine were not observed in any of the cell lines. The findings suggested that BI-D1870 alone exerts an adequate antiproliferative effect on AML with or without FLT3 mutations and serves as a novel AML therapeutic agent.

Bioisosteric replacements of the indole moiety for the development of a potent and selective PI3Kδ inhibitor: Design, synthesis and biological evaluation.

Based on indole scaffold, a potent and selective phosphoinositide 3-kinase delta (PI3Kδ) inhibitor, namely FD223, was developed by the bioisosteric replacement drug discovery approach and studied for the treatment of acute myeloid leukemia (AML). Invitro studies revealed that FD223 displays high potency (IC50=1nM) and selectivity (29-51 fold over other PI3K isoforms) against PI3Kδ, and exhibits efficient inhibition of the proliferation of AML cell lines (MOLM-16, HL-60, EOL-1 and KG-1) by suppressing p-AKT Ser473 thus causing G1 phase arrest during the cell cycle. Further given the favorable pharmacokinetic (PK) profiles of FD223, invivo studies were evaluated using xenograft model in nude mice, confirming its significant antitumor efficacy meanwhile with no observable toxicity. All these results are comparable to the positive group of Idelalisib (CAL-101), indicating that FD223 has potential for further development as a promising PI3Kδ inhibitor for the treatment of leukemia such as AML.

Azelaic Acid Exerts Antileukemia Effects against Acute Myeloid Leukemia by Regulating the Prdxs/ROS Signaling Pathway.

Acute myeloid leukemia (AML) is a hematological malignancy with a poor prognosis attributed to elevated reactive oxygen species (ROS) levels. Thus, agents that inhibit ROS generation in AML should be exploited. Azelaic acid (AZA), a small molecular compound, can scavenge ROS and other free radicals, exerting antitumor effects on various tumor cells. Herein, this study evaluated the antileukemic activity of AZA against AML via regulation of the ROS signaling pathway. We found that AZA reduced intracellular ROS levels and increased total antioxidant capacity in AML cell lines and AML patient cells. AZA suppressed the proliferation of AML cell lines and AML patient cells, expending minimal cytotoxicity on healthy cells. Laser confocal microscopy showed that AZA-treated AML cells surged and ruptured gradually on microfluidic chips. Additionally, AZA promoted AML cell apoptosis and arrested the cell cycle at the G1 phase. Further analysis demonstrated that peroxiredoxin (Prdx) 2 and Prdx3 were upregulated in AZA-treated AML cells. In vivo, AZA prolonged survival and attenuated AML by decreasing CD33+ immunophenotyping in the bone marrow of a patient-derived xenograft AML model. Furthermore, mice in the AZA-treated group had an increased antioxidant capacity and Prdx2/Prdx3 upregulation. The findings indicate that AZA may be a potential agent against AML by regulating the Prdxs/ROS signaling pathway.

Inhibition of CSRP2 Promotes Leukemia Cell Proliferation and Correlates with Relapse in Adults with Acute Myeloid Leukemia.

BackgroundRelapse is a major obstacle in the treatment of acute myeloid leukemia (AML). Refinement of risk stratification may aid the identification of patients who are likely to relapse. Abnormal cysteine and glycine-rich protein 2 (CSRP2) has been implicated in various cancers, but its function remains unclear. The purpose of this study was to explore the role of CSRP2 in predicting adult AML recurrence.MethodsRT-PCR was used to detect the expression of CSRP2 in 193 newly diagnosed adult AML patients and 44 healthy controls. The competitive risk model was used to calculate the cumulative incidence of relapse rate (CIR), Kaplan–Meier to calculate the relapse-free survival rate (RFS), and the Cox regression model to perform multivariate analysis. Viral transfection was used to construct AML cell lines with stable knockdown of CSRP2, CCK8 to detect proliferation and drug resistance, flow cytometry to detect cell cycle and apoptosis, and Western blot to detect key molecules in signaling pathways.ResultsCSRP2 transcript levels were higher in 193 adult AML compared with 44 healthy controls. In 149 patients who achieved complete remission, those with high CSRP2 transcript levels displayed a lower 2-year CIR and higher 2-year RFS, especially when receiving only chemotherapy. In multivariate analysis, a high CSRP2 transcript level was independently associated with a better RFS. Knockdown of CSRP2 promoted proliferation and cell cycle progression, and reduced chemosensitivity. Western blot analysis showed upregulation of p-AKT and p-CREB in CSRP2-knockdown AML cell lines. Inhibition assays suggested these two signaling pathways participated in the CSRP2-mediated proliferation effects in AML cell lines.ConclusionIn summary, CSRP2 correlates with relapse in adult AML. Down-regulation of CSRP2 could promote the proliferation of AML cell lines by regulating the AKT and CREB signaling pathways. Therefore, CSRP2 may provide prognostic significance and potential therapeutic targets in the management of AML.

Abstract 586: Anti-leukemia activities of selenium nanoparticles embedded in nanotube consisted of triple-helix β-D-glucan

Abstract Background: Acute myeloid leukemia (AML) is a hematological malignant tumor. The common chemotherapy results in various side-effect and drug-resistance for AML, so it is urgent to find a non-toxic natural drug for AML therapy. Herein, for the first time, the Se nanoparticles embedded in nanotube consisted of triple helix β-D-glucan (BFP) exhibit the high anti-leukemia effects. Methods: A triple helix β-(1, 3)-D-glucan (BFP) extracted from the black fungus was self-assembled into nanotube in water, and Se nanoparticles (SeNPs) were wrapped to form stable inclusion complex BFP-Se. The CCK8 assays, lactose dehydrogenase release assays, optofluidics chips and flow cytometry were used to test the anti-leukemia effects of BFP-Se in vitro and in vivo. Results: The SeNPs embedded in the BFP nanotubes exhibited high stability in water, avoiding aggregation and dispersion to out. In vitro, the BFP-Se significantly inhibited the proliferation of AML cell lines and patient cells and markedly increased the cytotoxicity on AML cells. BFP-Se slowed the Molm-13 GFP+ cells growth. On single-cell levels, the U937 cells were gradually swelled and lysed with BFP-Se treatment. In addition, BFP-Se had little toxic to hematopoietic stem cells (HSC) and T cells compared to Ara-c. Flow cytometry indicated that BFP-Se promoted the cell apoptosis and blocked cell cycle of AML cells. Further, after injection of BFP-Se, the survival was longer on AML PDX model constructed with B-NSG mice. The blood and bone marrow analysis indicated the anti-leukemia effects of BFP-Se in vivo. Moreover, BFP-Se extremely increased the total antioxidant capacity (T-AOC) of AML cells, and decreased the expression of c-Jun activation domain-binding protein-1 (Jab1) and thioredoxin 1 (Trx1). Conclusion: This biocompatible polysaccharide nanotube containing Se nanoparticles - against AML would provide a novel strategy for AML therapy. Citation Format: Yanxia Jin, Liqin Cai, Qian Yang, Ziyi Luo, Lina Zhang, Fuling Zhou. Anti-leukemia activities of selenium nanoparticles embedded in nanotube consisted of triple-helix β-D-glucan [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 586.

Chidamide Combined with Decitabine Synergistically Induce Apoptosis of Acute Myeloid Leukemia By up-Regulating Perp gene In Vivo and in Vitro

Background: Acute myeloid leukemia (AML) is a malignant clonal disease of hematopoietic stem cells. The long term survival of AML is not satisfactory, so new treatment should be explored. Here, we show that chidamide(CH), a histone deacetylase inhibitor, combined with decitabine(DE) induces apoptosis of AML cell lines and primary refractory/relapsed AML cells by up-regulating PERP. This may provide a new option for AML treatment. Methods and results: We first examined the half-inhibitory concentrations (IC50) of chidamide and decitabine against THP-1, MV4-11, HL60 and Kasumi-1 cell lines using MTT (Fig1 A-D). And the drug combination is performed according to the IC50. In the double-drug combination experiment, we used MTT to detect the effect of drugs on the proliferation of the four cell lines (Fig1 E-H), used calcusyn 2.0 software to calculate the synergistic effect (Fig2), flow cytometry to detect apoptosis (Fig3 A-D), and western blot to detect the pro-apoptotic protein (C-CASPASE 3 and C-CASPASE 9) and anti-apoptotic proteins (CASPASE 8, BCL-2 and BCL-XL) (Fig3 E-H). We found that chidamide combined with decitabine synergistically inhibited proliferation of AML cell lines, induced apoptosis, up-regulated pro-apoptotic protein levels and down-regulated anti-apoptotic protein levels. To investigate this combination therapeutic effect in vivo, we selected 5 refractory/relapsed AML patients, extracted primary AML cells, and used ATP chemiluminescence kit for drug sensitivity test. The results confirmed that four of the five patients with AML showed sensitivity to combinations (Fig4). To further explore the mechanism of action of CH combination with DE, we performed transcriptome sequencing (Fig5). Analysis of the sequencing results, the gene PERP, which shows the significant difference in the apoptotic pathway, was further examined. The PERP is a new member of the PMP-22/GAS3 family as an apoptosis-associated target of TP53. RT-QPCR and WB verified the role of PERP in apoptosis in DE and CH combination (Fig6). The results showed that the combination could up-regulate the PERP gene than the single drug. When we explored the role of the PERP gene in AML cell lines, we knocked down the PERP gene by lentivirus and detected cell proliferation after infection. Pretreated AML cell lines by lentivirus-infection (Fig7A-F), then we tested for proliferation (Fig7G-I) (Fig8A-C), apoptosis (Fig8D-E), and pro-apoptotic protein expression (Fig8G-I). The results showed that knocking down the PERP gene promoted the proliferation of AML cell lines and attenuated the sensitivity of AML cell lines to chemotherapeutic drugs. We also compare the mRNA level of PERP between 35 AML patients and 20 normal and found that the PERP mRNA of AML patients was significantly lower than the normal (Fig9). MV4-11 cells were exposed to CH and DE alone or in combination, and proteomic sequencing was performed to examine the effect of the drug on cellular protein. The result indicates to some extent that CH contributes more to the combined effect. And the drug causes changes in multiple pathways in the cell (Fig10). Conclusion: Our experiments revealed that CH combined with DE may have therapeutic effects on AML and, to some extent, reveal the mechanism of dual drug combination. Legends to figures Fig1. 50% inhibitory concentration (IC50) values of chidamide and decitabine alone treated AML cell lines. Fig2. Chidamide acts synergistically in AML with DE. Fig3. Chidamide in combination with decitabine significantly induced apoptosis in AML cell lines. Fig4. The sensitivity of relapsed or refractory AML primary cells to chidamide and decitabine alone or in combination. Fig5. Gene expression analysis showed an obvious difference based on treatment. Fig6. Verify transcriptome sequencing results by real-time QPCR and by western blotting with or without drug treatment. Fig7. The effect of down-regulation of PERP by Lentivirus-mediated RNAi on AML cells proliferation. Fig8. PERP knockdown causes AML cells to develop resistance to combination drugs. Fig9.The level of PERP mRNA in peripheral blood mononuclear cells of AML and normal humans. Fig10. Proteomics sequencing results show the differentially expressed protein and a cluster analysis of the functions or pathways enriched by differentially expressed proteins in GO and KEGG pathways compared to single agents. Disclosures No relevant conflicts of interest to declare.

Synergistic Effect of DHODH Inhibitor PTC299 with DNA Demethylating Agent Decitabine in Myelodysplastic Syndromes

Background:Myelodysplastic Syndrome (MDS) is a clonal bone marrow disorder characterized by ineffective and clonal hematopoiesis accompanied by morphological dysplasia and variable cytopenia. There are few treatment options for MDS, and allogenic hematopoietic stem cell transplantation is the only curative option. Dihydroorotate dehydrogenase (DHODH) catalyzes a rate-limiting step in de novo pyrimidine synthesis, the conversion of DHO to orotate. DHODH inhibition has been described recently as a new approach for treating acute myeloid leukemia (AML) by inducing differentiation of diverse AML subclasses. PTC299 represents a novel potent DHODH inhibitor and recently clinical development of PTC299 as a potential treatment option for acute leukemia was initiated. Here, we explored the efficacy of DHODH inhibitor PTC299 for MDS. Methods:Anti-MDS efficacy of PTC299 was studied using human MDS cell lines and primary MDS cells in vitro. PTC299 was synthesized at PTC Therapeutics Inc. Mechanistic studies were conducted via flow cytometric analysis and RNA-sequencing (RNA-seq). Gene expression levels were analyzed by quantitative PCR (qPCR). Results:PTC299 inhibited proliferation of AML cell lines and induced their differentiation. As previously reported in other DHODH inhibitors, upregulation of CD11b was observed after PTC299 treatment in both HL-60 and THP-1 cells. In addition, PTC299 inhibited the proliferation of MDS cell lines, MDSL and SKM-1 cells, with EC50s of 12.6 nM in MDSL cells and 19.7 nM in SKM-1 cells. The inhibitory effect was reversed by the exogenous addition of 100 µM uridine, which bypasses the requirement for de novo pyrimidine synthesis by feeding into the salvage pathway, thereby negating the need for DHODH. Because the basal expression levels of CD11b are high in MDS cells, we examined the expression levels of CD38. Both cell lines showed dose-dependent upregulation of CD38 after PTC299 treatment. To investigate the possible synergism between PTC299 and decitabine, we treated MDSL and SKM-1 cells with increasing concentrations of PTC299 and decitabine as single agents or in combination. After 3 days of culture, cells were analyzed by MTS assays. PTC299 and decitabine exerted a enhanced cytotoxic effect on MDSL and SKM-1 cells. Similar results were obtained with primary MDS samples. In Annexin/PI assays, the percentage of apoptotic cells was increased by combination of PTC299 with decitabine in both cell lines. Mechanistically, treatment with PTC299 induced an intra-S-phase arrestfollowed by entry intoapoptotic cell death. It has also been reported that the expression of p53 is increased in response to the intra-S-phase arrest. To understand the genome-wide effects and target genes of PTC299 and the combination with decitabine, we performed RNA-seq of MDSL and SKM-1 cells treated with PTC299, decitabine, or the combination of both agents versus DMSO-treated cells. Gene set enrichment analysis (GSEA) using our RNA-seq data confirmed that MYC target gene sets were negatively enriched in both PTC299-, decitabine- and combination- treated cells. KEGG pathway enrichment analysis revealed activation of genes associated with apoptosis in both cell lines. To better elucidate a synergistic effect of PTC299 and decitabine, we performed qPCR of CDKN1A, which is a major target of p53 activity. The mRNA expression levels of CDKN1A were upregulated after treatment with PTC299, which was further enhanced by the combination with decitabine. Conclusions:Our result indicate that the DHODH inhibitor PTC299 suppresses the growth of MDS cells in vitro and acts in at least an additive and possibly synergistic manner with decitabine in this process. This combination therapy could be a new therapeutic option for the treatment of MDS. Disclosures Lennox: PTC Therapeutics: Employment. Weetall:PTC Therapeutics: Employment. Sheedy:PTC Therapeutics: Employment.

PF240 COMBINED INHIBITION OF SHP1 AND SHP2 WITH PHORBOL ESTERS AS A DIFFERENTIATION THERAPY AGAINST ACUTE MYELOID LEUKEMIA

Background:The differentiation‐based therapy for acute promyelocytic leukemia (APL) is an inspiring example for the search of novel strategies aimed at treatment of other subtypes of acute myeloid leukemia (AML). Thus, the discovery of new molecular players in cell differentiation becomes a paramount research area to achieve this goal.Aims:To assess the involvement of the protein tyrosine phosphatases SHP1 and SHP2 on leukemic cells differentiation along with the therapeutic possibilities of their targeting to enhance the differentiation induction effect of phorbol esters.Methods:The oxidation status and enzymatic activity of SHP1 and SHP2 during PMA‐induced differentiation of HEL cells was evaluated. Additionally, the effects of RNAi‐mediated downregulation of these phosphatases on cell differentiation was studied. Afterwards, the impact of chemical inhibition of SHP1 and SHP2 on differentiation both in the presence and absence of phorbol esters was tested. Finally, the anti‐leukemic potential of phorbol esters and chemical inhibitors of SHP1 and SHP2 was addressed in several AML model cell lines, a xenograft mouse model and AML primary cells in vitro. Results:An increase of oxidation with a concomitant decrease of activity was observed for both phosphatases at the onset of PMA‐induced differentiation. Consistently, silencing of these proteins favored the process, with an enhanced effect upon their simultaneous downregulation. Moreover, the proteins SRC and β‐catenin were identified as downstream targets of SHP1 and SHP2 in this context. In agreement with these findings, chemical inhibition of the phosphatases promoted cell differentiation itself and enhanced the effect of phorbol esters. Interestingly, treatment with the phorbol ester prostratin and the dual inhibitor of SHP1 and SHP2 NSC87877 synergistically hampered the proliferation of AML cell lines, prolonged the survival of xenografted mice and reduced the clonogenic potential of AML primary cells.Summary/Conclusion:SHP1 and SHP2 are relevant mediators of differentiation in AML cells and their inhibition either alone or in combination with prostratin seems a promising differentiation‐based therapeutic strategy against different subtypes of AML beyond APL.

SHP1 and SHP2 inhibition enhances the pro-differentiative effect of phorbol esters: an alternative approach against acute myeloid leukemia

BackgroundThe differentiation-based therapy for acute promyelocytic leukemia (APL) is an inspiring example for the search of novel strategies aimed at treatment of other subtypes of acute myeloid leukemia (AML). Thus, the discovery of new molecular players in cell differentiation becomes a paramount research area to achieve this goal. Here, the involvement of the protein tyrosine phosphatases SHP1 and SHP2 on leukemic cells differentiation is shown, along with the therapeutic possibilities of their targeting to enhance the differentiation induction effect of phorbol esters.MethodsThe oxidation status and enzymatic activity of SHP1 and SHP2 during PMA-induced differentiation of HEL cells was evaluated. Additionally, the effects of RNAi-mediated downregulation of these phosphatases on cell differentiation was studied. Afterwards, the impact of chemical inhibition of SHP1 and SHP2 on differentiation both in the presence and absence of phorbol esters was tested. Finally, the anti-leukemic potential of phorbol esters and chemical inhibitors of SHP1 and SHP2 was addressed in several AML model cell lines, a xenograft mouse model and AML primary cells in vitro.ResultsAn increase of oxidation with a concomitant decrease of activity was observed for both phosphatases at the onset of PMA-induced differentiation. Consistently, silencing of these proteins favored the process, with an enhanced effect upon their simultaneous downregulation. Moreover, the proteins SRC and β-catenin were identified as downstream targets of SHP1 and SHP2 in this context. In agreement with these findings, chemical inhibition of the phosphatases promoted cell differentiation itself and enhanced the effect of phorbol esters. Interestingly, treatment with the phorbol ester prostratin and the dual inhibitor of SHP1 and SHP2 NSC87877 synergistically hampered the proliferation of AML cell lines, prolonged the survival of xenografted mice and reduced the clonogenic potential of AML primary cells.ConclusionsSHP1 and SHP2 are relevant mediators of differentiation in AML cells and their inhibition either alone or in combination with prostratin seems a promising differentiation-based therapeutic strategy against different subtypes of AML beyond APL.

A Potential Mechanism for the Antioxidant Compound Kushen Injection Targeting the ROS Signaling Pathway in Acute Myeloid Leukemia

AbstractIt is a challenge for treatment of acute myeloid leukemia (AML) in clinic. The increase in the levels of reactive oxygen species (ROS) in AML patients has been previously described; thus, it is important to regulate ROS levels in AML.In this study, we found that intracellular ROS levels in AML cells were decreased, the total antioxidant capacity (T-AOC) and glutathione (GSH) contents were increased and xanthine oxidase (XOD) vitality was decreased when treated with the compound kushen injection (CKI). This shows that CKI inhibited the proliferation of AML cell lines and patient cells and enhanced the cytotoxicity of AML cells, which has few toxic effects on haematopoietic stem cells (HSCs) and T cells. At the single-cell level, individual AML cells died gradually by CKI treatment on optofluidic chips. CKI could promote apoptosis and arrest cell cycle at G1/G0 phase in U937 cells.Furthermore, higher peroxiredoxin-3 (Prdx3) expression levels were found in CKI-treated U937 cells through quantitative proteomics detection. Mechanically, the expression of Prdx3 and peroxiredoxin-2 (Prdx2) was up-regulated in CKI-treated AML cells, while thioredoxin 1 (Trx1) was reduced. Laser confocal microscopy showed that the Prdx2 and Trx1 proteins could be co-localized by CKI treatment.In vivo, in the CKI-treated group, survival was longer in an AML patient-derived xenograft model in B-NSG mice. The disease was partially alleviated by decreased CD45+ immunophenotyping in peripheral blood and bone marrow smear analysis. After CKI injection, the T-AOC vitality, GSH content and CAT activity increased and the concentration of H2O2decreased in mouse plasma. A bone marrow biopsy and immunohistochemistry analysis showed that Prdx3 and Prdx2 expression was increased, while Trx1 expression was decreased.In a conclusion, we provided a model for the anti-leukaemic effects of CKI. CKI decreased intracellular ROS levels by up-regulating the expression of Prdx2 in the cytoplasm and Prdx3 in the mitochondria and down-regulating Trx1 expression, which maintained the intracellular REDOX and further inhibited AML cell proliferation.Therefore, antioxidant CKI is a promising drug for the treatment of AML in the clinic. We aimed to explore the therapeutic efficacy of low toxicity natural antioxidants against AML by targeting ROS pathways and providing new strategies to improve survival in AML patients. DisclosuresNo relevant conflicts of interest to declare.

Combined Metabolic Targeting With Metformin and the NSAIDs Diflunisal and Diclofenac Induces Apoptosis in Acute Myeloid Leukemia Cells

The accelerated metabolism of tumor cells, inevitable for maintaining high proliferation rates, is an emerging target for tumor therapy. Increased glucose and lipid metabolism as well as mitochondrial activity have been shown in solid tumors but also in leukemic cells. As tumor cells are able to escape the blockade of one metabolic pathway by a compensatory increase in other pathways, treatment strategies simultaneously targeting metabolism at different sites are currently developed. However, the number of clinically applicable anti-metabolic drugs is still limited. Here, we analyzed the impact of the anti-diabetic drug metformin alone or in combination with two non-steroidal anti-inflammatory drugs (NSAIDs) diclofenac and diflunisal on acute myeloid leukemia (AML) cell lines and primary patient blasts. Diclofenac but not diflunisal reduced lactate secretion in different AML cell lines (THP-1, U937, and KG-1) and both drugs increased respiration at low concentrations. Despite these metabolic effects, both NSAIDs showed a limited effect on tumor cell proliferation and viability up to a concentration of 0.2 mM. In higher concentrations of 0.4–0.8 mM diflunisal alone exerted a clear effect on proliferation of AML cell lines and blocked respiration. Single treatment with the anti-diabetic drug metformin blocked mitochondrial respiration, but proliferation and viability were not affected. However, combining all three drugs exerted a strong cytostatic and cytotoxic effect on THP-1 cells. Comparable to the results obtained with THP-1 cells, the combination of all three drugs significantly reduced proliferation of primary leukemic blasts and induced apoptosis. Furthermore, NSAIDs supported the effect of low dose chemotherapy with cytarabine and reduced proliferation of primary AML blasts. Taken together we show that low concentrations of metformin and the two NSAIDs diclofenac and diflunisal exert a synergistic inhibitory effect on AML proliferation and induce apoptosis most likely by blocking tumor cell metabolism. Our results underline the feasibility of applying anti-metabolic drugs for AML therapy.

Discovery of N2-(4-Amino-cyclohexyl)-9-cyclopentyl- N6-(4-morpholin-4-ylmethyl-phenyl)- 9H-purine-2,6-diamine as a Potent FLT3 Kinase Inhibitor for Acute Myeloid Leukemia with FLT3 Mutations.

FLT3 tyrosine kinase is a potential drug target in acute myeloid leukemia (AML) because patients with FLT3-ITD mutations respond poorly to standard cytotoxic agents and there is a clear link between the disease and the oncogenic properties of FLT3. We present novel 2,6,9-trisubstituted purine derivatives with potent FLT3 inhibitory activity. The lead compound 7d displays nanomolar activity in biochemical assays and selectively blocks proliferation of AML cell lines harboring FLT3-ITD mutations, whereas other transformed and normal human cells are several orders of magnitude less sensitive. The MV4-11 cells treated with 7d suppressed the phosphorylation of FLT3 and its downstream signaling pathways, with subsequent G1 cell cycle arrest and apoptosis. Additionally, a single dose of 7d in mice with subcutaneous MV4-11 xenografts caused sustained inhibition of FLT3 and STAT5 phosphorylation over 48 h, in contrast to the shorter effect observed after administration of the reference FLT3 inhibitor quizartinib.