Panobinostat enhances cytarabine and daunorubicin sensitivities in AML cells through suppressing the expression of BRCA1, CHK1, and Rad51

Panobinostat sensitizes AraC-resistant AML cells to the combination of azacitidine and venetoclax

The majority of acute myeloid leukemia (AML) patients respond to intensive induction therapy, consisting of cytarabine (AraC) and an anthracycline, though more than half experience relapse. Relapsed/refractory (R/R) AML patients are difficult to treat, and their clinical outcomes remain dismal. Venetoclax (VEN) in combination with azacitidine (AZA) has provided a promising treatment option for R/R AML, though the overall survival (OS) could be improved (OS ranges from 4.3 to 9.1 months). Overexpression of c-Myc is associated with chemoresistance in AML. Histone deacetylase (HDAC) inhibitors have been shown to suppress c-Myc and enhance the antileukemic activity of VEN, as well as AZA, though combination of all three has not been fully explored. In this study, we investigated the HDAC inhibitor, panobinostat, in combination with VEN + AZA against AraC-resistant AML cells. Panobinostat treatment downregulated c-Myc and Bcl-xL and upregulated Bim, which enhanced the antileukemic activity of VEN + AZA against AraC-resistant AML cells. In addition, panobinostat alone and in combination with VEN + AZA suppressed oxidative phosphorylation and/or glycolysis in AraC-resistant AML cells. These findings support further development of panobinostat in combination with VEN + AZA for the treatment of AraC-resistant AML.

Mitocurcumin utilizes oxidative stress to upregulate JNK/p38 signaling and overcomes Cytarabine resistance in acute myeloid leukemia

Acute myeloid leukemia (AML) is a type of blood cancer that is characterized by the rapid growth of abnormal myeloid cells. The goal of AML treatment is to eliminate the leukemic blasts, which is accomplished through intensive chemotherapy. Cytarabine is a key component of the standard induction chemotherapy regimen for AML. However, despite a high remission rate, 70-80% of AML patients relapse and develop resistance to Cytarabine, leading to poor clinical outcomes. Mitocurcumin (MitoC), a derivative of curcumin that enters mitochondria, leading to a drop in mitochondrial membrane potential and mitophagy induction. Further, it activates oxidative stress-mediated JNK/p38 signaling to induce apoptosis. MitoC demonstrated a preferential ability to kill leukemic cells from AML cell lines and patient-derived leukemic blasts. RNA sequencing data suggests perturbation of DNA damage response and cell proliferation pathways in MitoC-treated AML. Elevated reactive oxygen species (ROS) in MitoC-treated AML cells resulted in significant DNA damage and cell cycle arrest. Further, MitoC treatment resulted in ROS-mediated enhanced levels of p21, which leads to suppression of CHK1, RAD51, Cyclin-D and c-Myc oncoproteins, potentially contributing to Cytarabine resistance. Combinatorial treatment of MitoC and Cytarabine has shown synergism, increased apoptosis, and enhanced DNA damage. Using AML xenografts, a significant reduction of hCD45+ cells was observed in AML mice bone marrow treated with MitoC (mean 0.6%; range0.04%-3.56%) compared to control (mean 38.2%; range10.1%-78%), p = 0.03. The data suggest that MitoC exploits stress-induced leukemic oxidative environment to up-regulate JNK/p38 signaling to lead to apoptosis and can potentially overcome Cytarabine resistance via ROS/p21/CHK1 axis.

E2F1 rs3213150 polymorphism influences cytarabine sensitivity and prognosis in patients with acute myeloid leukemia

Cytarabine (Ara-C) plays an irreplaceable role in the treatment of acute myeloid leukemia (AML). However, there are significant differences in efficacy among patients. Our previous studies found that E2F1 rs3213150 polymorphism was associated with remission rate of Ara-C chemotherapy, but the specific mechanism is not clear. This study aimed to further confirm the correlation between E2F1 rs3213150 polymorphism and Ara-C resistance and prognosis in AML patients, and to provide valuable information for elucidating the molecular mechanisms involved.

METHODS

Rs3213150 genotyping was performed in 922 AML patients by Sanger sequencing, and the effects of different genotypes on chemosensitivity and prognosis were analyzed by Logistic regression and Cox regression. Meanwhile, a prediction model of Ara-C chemotherapy resistance was established. The impact of rs3213150 polymorphism on E2F1 expression level was determined by luciferase reporter gene assay, and differentially expressed genes between patients with different genotypes were identified by RNA sequencing.

RESULTS

Compared with rs3213150 G allele carriers, patients with AA genotype had more obvious Ara-C resistance (41.94% vs. 27.94%, P = 0.002), shorter overall survival (529 d vs. 644 d, P = 0.008) and disease-free survival (519 d vs. 556 d, P = 0.023). Rs3213150G > A mutation resulted in decreased E2F1 expression.

CONCLUSION

E2F1 rs3213150 polymorphism influences the chemosensitivity and prognosis of Ara-C in Chinese AML patients.

Acquired resistance to venetoclax plus azacitidine in acute myeloid leukemia: In vitro models and mechanisms

The combination of venetoclax (VEN) and azacitidine (AZA) has become the standard of care for acute myeloid leukemia (AML) patients who are ≥ 75 years or unfit for intensive chemotherapy. Though initially promising, resistance to the combination therapy is an issue and VEN + AZA-relapsed/refractory patients have dismal outcomes. To better understand the mechanisms of resistance, we developed VEN + AZA-resistant AML cell lines, MV4-11/VEN + AZA-R and ML-2/VEN + AZA-R, which show > 300-fold persistent resistance compared to the parental lines. We demonstrate that these cells have unique metabolic profiles, including significantly increased levels of cytidine triphosphate (CTP) and deoxycytidine triphosphate (dCTP), changes in fatty acid and amino acid metabolism and increased utilization and reliance on glycolysis. Furthermore, fatty acid transporter CD36 is increased in the resistant cells compared to the parental cells. Inhibition of glycolysis with 2-Deoxy-D-glucose re-sensitized the resistant cells to VEN + AZA. In addition, the VEN + AZA-R cells have increased levels of the antiapoptotic protein Mcl-1 and decreased levels of the pro-apoptotic protein Bax. Overexpression of Mcl-1 or knockdown of Bax result in resistance to VEN + AZA. Our results provide insight into the molecular mechanisms contributing to VEN + AZA resistance and assist in the development of novel therapeutics to overcome this resistance in AML patients.

PARP-1 improves leukemia outcomes by inducing parthanatos during chemotherapy

Previous chemotherapy research has focused almost exclusively on apoptosis. Here, a standard frontline drug combination of cytarabine and idarubicin induces distinct features of caspase-independent, poly(ADP-ribose) polymerase 1 (PARP-1)-mediated programmed cell death "parthanatos" in acute myeloid leukemia (AML) cell lines (n = 3/10 tested), peripheral blood mononuclear cells from healthy human donors (n = 10/10 tested), and primary cell samples from patients with AML (n = 18/39 tested, French-American-British subtypes M4 and M5). A 3-fold improvement in survival rates is observed in the parthanatos-positive versus -negative patient groups (hazard ratio [HR] = 0.28-0.37, p = 0.002-0.046). Manipulation of PARP-1 activity in parthanatos-competent cells reveals higher drug sensitivity in cells that have basal PARP-1 levels as compared with those subjected to PARP-1 overexpression or suppression. The same trends are observed in RNA expression databases and support the conclusion that PARP-1 can have optimal levels for favorable chemotherapeutic responses.

Phase 1 study of belinostat and adavosertib in patients with relapsed or refractory myeloid malignancies

PURPOSE

Belinostat is an intravenous histone deacetylase inhibitor with approval for T-cell lymphomas. Adavosertib is a first in class oral Wee1 inhibitor. Preclinical studies of the combination demonstrated synergy in various human acute myeloid leukemia (AML) lines as well as AML xenograft mouse models.

EXPERIMENTAL DESIGN

This was a phase 1 dose-escalation study of belinostat and adavosertib in patients with relapsed/refractory AML and myelodysplastic syndrome (MDS). Patients received both drugs on days 1-5 and 8-12 of a 21-day cycle. Safety and toxicity were monitored throughout the study. Plasma levels of both drugs were measured for pharmacokinetic analysis. Response was determined by standard criteria including bone marrow biopsy.

RESULTS

Twenty patients were enrolled and treated at 4 dose levels. A grade 4 cytokine release syndrome at dose level 4 (adavosertib 225 mg/day; belinostat 1000 mg/m2) qualified as a dose-limiting toxicity event. The most common non-hematologic treatment-related adverse events were nausea, vomiting, diarrhea, dysgeusia, and fatigue. No responses were seen. The study was terminated prior to maximum tolerated dose/recommended phase 2 dose determination.

CONCLUSIONS

The combination of belinostat and adavosertib at the tested dose levels was feasible but without efficacy signals in the relapsed/refractory MDS/AML population.

Construction of circRNA-miRNA-mRNA Network Reveal Functional circRNAs and Key Genes in Acute Myeloid Leukemia

Introduction

CircRNA is closely correlated with a wide variety of processes of acute myeloid leukemia (AML), whereas the novel circRNAs, their molecular mechanism and the specific function they played in AML should be explored in depth.

Methods

The microarray chip data of AML patients and normal samples in the Gene Expression Omnibus (GEO) database were selected to differentially expressed (DE) circRNA, miRNA, and mRNA genes. The miRNA gene was the intersection of the circRNA target gene predicted using CSCD and the miRNA gene screened from AML patients, while the mRNA gene was the intersection of the target gene mRNA of miRNA predicted using miRanda and miRTarBase software and the mRNA gene screened from AML patients. The hub mRNAs related to survival were further screened through Cox proportional hazard regression. CircRNA/miRNA/mRNA interaction network was constructed by using Cytoscape software.10 circRNAs and 6 miRNAs in bone marrow mononuclear cells (BMMNCs) of AML patients (n=43) and healthy controls (n=35) were determined by RT-qPCR. Correlations between them were analyzed by Pearson correlation coefficient.

Results

10 circRNAs, 6 miRNAs, and 33 mRNAs were identified. Subsequently, the network of circRNAs, miRNAs, and hub genes was built using Cystoscope. Four key circRNAs, seven hub genes and their regulatory pathways were identified. The result of RT-qPCRs showed that hsa_circ_0009581 and hsa_circ_0005273 were significantly upregulated in AML patients while hsa_circ_0000497 and hsa_circ_0001947 were significantly downregulated. Hsa-miR-150-5p was significantly downregulated; hsa-miR-454-3p was upregulated in AML patients. Hsa_circ_0009581 and hsa-miR-150-5p; hsa_ circ_0001947 and hsa-miR-454-3p were inversely correlated using Pearson's correlation coefficient.

Conclusion

This study suggests that differentially expressed circRNAs take on a critical significance to AML development and may be the effective therapeutic targets. We suppose that hsa_circ_0009581 promotes leukemia development through hsa-miR-150-5p and hsa_circ_0001947 through hsa-miR-454-3p. hsa_circ_0001947 and hsa_circ_0009581 may provide new directions in the pathogenesis of AML.

Co-targeting of HDAC, PI3K, and Bcl-2 results in metabolic and transcriptional reprogramming and decreased mitochondrial function in acute myeloid leukemia

Despite the recently approved new therapies, the clinical outcomes of acute myeloid leukemia (AML) patients remain disappointing, highlighting the need for novel therapies. Our lab has previously demonstrated the promising outlook for CUDC-907, a dual inhibitor of PI3K and HDAC, in combination with venetoclax (VEN), against AML both in vitro and in vivo at least partially through suppression of c-Myc. In this study, we further elucidated the mechanism of action of the combination in preclinical models of AML. We demonstrated that the combination significantly reduced primary AML cell engraftment in immunocompromised mice. RNA sequencing and metabolomics analyses revealed that the combination reduced the levels for mRNAs of key TCA cycle genes and metabolites in the TCA cycle, respectively. This was accompanied by a reduced oxygen consumption rate (OCR), demonstrating that the combination suppressed oxidative phosphorylation (OXPHOS). Metabolomics analyses revealed that a large number of metabolites upregulated in AraC-resistant AML cells could be downregulated by the combination. CUDC-907 synergized with VEN in inducing apoptosis in the AraC-resistant AML cells. In conclusion, the CUDC-907 and VEN combination induces metabolic and transcriptomic reprograming and suppression of OXPHOS in AML, which provides additional mechanisms underlying the synergy between the two agents.

Inhibition of Mcl-1 Synergistically Enhances the Antileukemic Activity of Gilteritinib and MRX-2843 in Preclinical Models of FLT3-Mutated Acute Myeloid Leukemia

FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication (FLT3-ITD) mutations occur in about 25% of all acute myeloid leukemia (AML) patients and confer a poor prognosis. FLT3 inhibitors have been developed to treat patients with FLT3-mutated AML and have shown promise, though the acquisition of resistance occurs, highlighting the need for combination therapies to prolong the response to FLT3 inhibitors. In this study, we investigated the selective Mcl-1 inhibitor AZD5991 in combination with the FLT3 inhibitors gilteritinib and MRX-2843. The combinations synergistically induce apoptosis in AML cell lines and primary patient samples. The FLT3 inhibitors downregulate c-Myc transcripts through the suppression of the MEK/ERK and JAK2/STAT5 pathways, resulting in the decrease in c-Myc protein. This suppression of c-Myc plays an important role in the antileukemic activity of AZD5991. Interestingly, the suppression of c-Myc enhances AZD5991-inudced cytochrome c release and the subsequent induction of apoptosis. AZD5991 enhances the antileukemic activity of the FLT3 inhibitors gilteritinib and MRX-2843 against FLT3-mutated AML in vitro, warranting further development.

c-Myc plays a critical role in the antileukemic activity of the Mcl-1-selective inhibitor AZD5991 in acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive disease with a low 5-year overall survival rate of 29.5%. Thus, more effective therapies are in need to prolong survival of AML patients. Mcl-1 is overexpressed in AML and is associated with poor prognosis, representing a promising therapeutic target. The oncoprotein c-Myc is also overexpressed in AML and is a significant prognostic factor. In addition, Mcl-1 is required for c-Myc induced AML, indicating that c-Myc-driven AML harbors a Mcl-1 dependency and co-targeting of Mcl-1 and c-Myc represents a promising strategy to eradicate AML. In this study, we investigated the role of c-Myc in the antileukemic activity of Mcl-1 selective inhibitor AZD5991 and the antileukemic activity of co-targeting of Mcl-1 and c-Myc in preclinical models of AML. We found that c-Myc protein levels negatively correlated with AZD5991 EC₅₀s in AML cell lines and primary patient samples. AZD5991 combined with inhibition of c-Myc synergistically induced apoptosis in AML cell lines and primary patient samples, and cooperatively targeted leukemia progenitor cells. AML cells with acquired resistance to AZD5991 were resensitized to AZD5991 when c-Myc was inhibited. The combination also showed promising and synergistic antileukemic activity in vitro against AML cell lines with acquired resistance to the main chemotherapeutic drug AraC and primary AML cells derived from a patient at relapse post chemotherapy. The oncoprotein c-Myc represents a potential biomarker of AZD5991 sensitivity and inhibition of c-Myc synergistically enhances the antileukemic activity of AZD5991 against AML.

Prevention of anticancer therapy-induced neurotoxicity: putting DNA damage in perspective

Chemotherapy-induced peripheral neuropathy (CIPN) is a severe side effect of conventional cancer therapeutics (cAT) that significantly impacts the quality of life of tumor patients. The molecular mechanisms of CIPN are incompletely understood and there are no effective preventive or therapeutic measures available to date. Here, we present a brief overview of the current knowledge about mechanisms underlying CIPN and discuss DNA damage-related stress responses as feasible targets for the prevention of CIPN. In addition, we discuss that the nematode Caenorhabditis elegans is a useful 3R-conform model organism to further elucidate molecular mechanisms of CIPN and to identify novel lead compounds protecting from cAT-triggered neuropathy.

Chidamide Reverses Fluzoparib Resistance in Triple-Negative Breast Cancer Cells

Poly (ADP-ribose) polymerase inhibitor (PARPi) resistance is a new challenge for antitumor therapy. The purpose of this study was to investigate the reversal effects of chidamide on fluzoparib resistance, a PARPi, and its mechanism of action. A fluzoparib-resistant triple-negative breast cancer (TNBC) cell line was constructed, and the effects of chidamide and fluzoparib on drug-resistant cells were studied in vitro and in vivo. The effects of these drugs on cell proliferation, migration, invasiveness, the cell cycle, and apoptosis were detected using an MTT assay, wound-healing and transwell invasion assays, and flow cytometry. Bioinformatics was used to identify hub drug resistance genes and Western blots were used to assess the expression of PARP, RAD51, MRE11, cleaved Caspase9, and P-CDK1. Xenograft models were established to analyze the effects of these drugs on nude mice. In vivo results showed that chidamide combined with fluzoparib significantly inhibited the proliferation, migration, and invasiveness of drug-resistant cells and restored fluzoparib sensitivity to drug-resistant cells. The combination of chidamide and fluzoparib significantly inhibited the expression of the hub drug resistance genes RAD51 and MRE11, arrested the cell cycle at the G2/M phase, and induced cell apoptosis. The findings of this work show that chidamide combined with fluzoparib has good antineoplastic activity and reverses TNBC cell resistance to fluzoparil by reducing the expression levels of RAD51 and MRE11.

Cotargeting of Bcl-2 and Mcl-1 shows promising antileukemic activity against AML cells including those with acquired cytarabine resistance

Acute myeloid leukemia (AML) remains a clinical challenge. Venetoclax is an effective Bcl-2 selective inhibitor approved by the U.S. Food and Drug Administration (FDA) for treatment of AML in patients who are 75 years and older or who have comorbidities. However, resistance to venetoclax limits its clinical efficacy. Mcl-1 has been identified as one determinant of resistance to venetoclax treatment. In this study, we investigate the Mcl-1 inhibitor S63845 in combination with venetoclax in AML cells. We found that S63845 synergizes with venetoclax in AML cell lines and primary patient samples. Bak/Bax double knockdown and treatment with the pan-caspase inhibitor Z-VAD-FMK revealed that the combination induces intrinsic apoptosis in AML cells. Inhibition of Mcl-1 using another Mcl-1 selective inhibitor, AZD5991, also synergistically enhanced apoptosis induced by venetoclax in a caspase-dependent manner. Importantly, S63845 in combination with venetoclax can effectively combat AML cells with acquired resistance to the standard chemotherapy drug cytarabine. In light of these facts, the combined inhibition of Mcl-1 and Bcl-2 shows promise against AML cells, including relapse/refractory AML.

Inhibitors of class I HDACs and of FLT3 combine synergistically against leukemia cells with mutant FLT3

Acute myeloid leukemia (AML) with mutations in the FMS-like tyrosine kinase (FLT3) is a clinically unresolved problem. AML cells frequently have a dysregulated expression and activity of epigenetic modulators of the histone deacetylase (HDAC) family. Therefore, we tested whether a combined inhibition of mutant FLT3 and class I HDACs is effective against AML cells. Low nanomolar doses of the FLT3 inhibitor (FLT3i) AC220 and an inhibition of class I HDACs with nanomolar concentrations of FK228 or micromolar doses of the HDAC3 specific agent RGFP966 synergistically induce apoptosis of AML cells that carry hyperactive FLT3 with an internal tandem duplication (FLT3-ITD). This does not occur in leukemic cells with wild-type FLT3 and without FLT3, suggesting a preferential toxicity of this combination against cells with mutant FLT3. Moreover, nanomolar doses of the new FLT3i marbotinib combine favorably with FK228 against leukemic cells with FLT3-ITD. The combinatorial treatments potentiated their suppressive effects on the tyrosine phosphorylation and stability of FLT3-ITD and its downstream signaling to the kinases ERK1/ERK2 and the inducible transcription factor STAT5. The beneficial pro-apoptotic effects of FLT3i and HDACi against leukemic cells with mutant FLT3 are associated with dose- and drug-dependent alterations of cell cycle distribution and DNA damage. This is linked to a modulation of the tumor-suppressive transcription factor p53 and its target cyclin-dependent kinase inhibitor p21. While HDACi induce p21, AC220 suppresses the expression of p53 and p21. Furthermore, we show that both FLT3-ITD and class I HDAC activity promote the expression of the checkpoint kinases CHK1 and WEE1, thymidylate synthase, and the DNA repair protein RAD51 in leukemic cells. A genetic depletion of HDAC3 attenuates the expression of such proteins. Thus, class I HDACs and hyperactive FLT3 appear to be valid targets in AML cells with mutant FLT3.

The combination of CUDC-907 and gilteritinib shows promising in vitro and in vivo antileukemic activity against FLT3-ITD AML

About 25% of patients with acute myeloid leukemia (AML) harbor FMS-like tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) mutations and their prognosis remains poor. Gilteritinib is a FLT3 inhibitor approved by the US FDA for use in adult FLT3-mutated relapsed or refractory AML patients. Monotherapy, while efficacious, shows short-lived responses, highlighting the need for combination therapies. Here we show that gilteritinib and CUDC-907, a dual inhibitor of PI3K and histone deacetylases, synergistically induce apoptosis in FLT3-ITD AML cell lines and primary patient samples and have striking in vivo efficacy. Upregulation of FLT3 and activation of ERK are mechanisms of resistance to gilteritinib, while activation of JAK2/STAT5 is a mechanism of resistance to CUDC-907. Gilteritinib and CUDC-907 reciprocally overcome these mechanisms of resistance. In addition, the combined treatment results in cooperative downregulation of cellular metabolites and persisting antileukemic effects. CUDC-907 plus gilteritinib shows synergistic antileukemic activity against FLT3-ITD AML in vitro and in vivo, demonstrating strong translational therapeutic potential.

Therapeutic Use of Valproic Acid and All-Trans Retinoic Acid in Acute Myeloid Leukemia-Literature Review and Discussion of Possible Use in Relapse after Allogeneic Stem Cell Transplantation

Even though allogeneic stem cell transplantation is the most intensive treatment for acute myeloid leukemia (AML), chemo-resistant leukemia relapse is still one of the most common causes of death for these patients, as is transplant-related mortality, i.e., graft versus host disease, infections, and organ damage. These relapse patients are not always candidates for additional intensive therapy or re-transplantation, and many of them have decreased quality of life and shortened expected survival. The efficiency of azacitidine for treatment of posttransplant AML relapse has been documented in several clinical trials. Valproic acid is an antiepileptic fatty acid that exerts antileukemic activity through histone deacetylase inhibition. The combination of valproic acid and all-trans retinoic acid (ATRA) is well tolerated even by unfit or elderly AML patients, and low-toxicity chemotherapy (e.g., azacitidine) can be added to this combination. The triple combination of azacitidine, valproic acid, and ATRA may therefore represent a low-intensity and low-toxicity alternative for these patients. In the present review, we review and discuss the general experience with valproic acid/ATRA in AML therapy and we discuss its possible use in low-intensity/toxicity treatment of post-allotransplant AML relapse. Our discussion is further illustrated by four case reports where combined treatments with sequential azacitidine/hydroxyurea, valproic acid, and ATRA were used.

ONC201 induces the unfolded protein response (UPR) in high- and low-grade ovarian carcinoma cell lines and leads to cell death regardless of platinum sensitivity

Objectives

Treatment of both platinum resistant high grade (HG) and low‐grade (LG) ovarian cancer (OVCA) poses significant challenges as neither respond well to conventional chemotherapy leading to morbidity and mortality. Identification of novel agents that can overcome chemoresistance is therefore critical. Previously, we have demonstrated that OVCA has basal upregulated unfolded protein response (UPR) and that targeting cellular processes leading to further and persistent upregulation of UPR leads to cell death. ONC201 is an orally bioavailable Dopamine Receptor D2 inhibitor demonstrating anticancer activity and was found to induce UPR. Given its unique properties, we hypothesized that ONC201 would overcome platinum resistance in OVCA.

Methods

Cisplatin sensitive and resistant HG OVCA and two primary LG OVCA cell lines were studied. Cell viability was determined using MTT assay. Cell migration was studied using wound healing assay. Apoptosis and mitochondrial membrane potential were investigated using flow cytometry. Analysis of pathway inhibition was performed by Western Blot. mRNA expression of UPR related genes were measured by qPCR. In vivo studies were completed utilizing axillary xenograft models. Co‐testing with conventional chemotherapy was performed to study synergy.

Results

ONC201 significantly inhibited cell viability and migration in a dose dependent manner with IC50’s from 1‐20 µM for both cisplatin sensitive and resistant HG and LG‐OVCA cell lines. ONC201 lead to upregulation of the pro‐apoptotic arm of the UPR, specifically ATF‐4/CHOP/ATF3 and increased the intrinsic apoptosispathway. The compensatory, pro‐survival PI3K/AKT/mTOR pathway was downregulated. In vivo, weekly dosing of single agent ONC201 decreased xenograft tumor size by ~50% compared to vehicle. ONC201 also demonstrated significant synergy with paclitaxel in a highly platinum resistant OVCA cell‐line (OV433).

Conclusions

Our findings demonstrate that ONC201 can effectively overcome chemoresistance in OVCA cells by blocking pro‐survival pathways and inducing the apoptotic arm of the UPR. This is a promising, orallybioavailable therapeutic agent to consider in clinical trials for patients with both HG and LG OVCA.

Improved Survival of Leukemic Mice Treated with Sodium Caseinate in Combination with Daunorubicin without Toxicity

In recent years, low doses of chemotherapy have been resumed and explored for the treatment of acute myeloid leukemia. Thus, CPX-351, a dual-drug liposomal encapsulation of cytarabine and daunorubicin, was approved by the US Food and Drug Administration, to deliver a synergistic 5 : 1 molar drug ratio into leukemia cells to a greater extent than normal bone marrow cells and significantly enhance survival compared with conventional treatment in older and newly diagnosed AML patients, but overall survival rate remains low; therefore, the need for new therapeutic options continues. Sodium caseinate (SC), a salt of casein, the main milk protein, has cytotoxic effect in leukemia cell lines, but promotes proliferation of hematopoietic normal cells, while its administration in leukemic mice promotes survival for more than 40 days, but bone marrow surviving mice still harbour leukemic cells, but it is not known whether the combination with cytarabine or daunorubicin can improve survival without damaging normal hematopoietic cells. Here, it is shown that, in vitro, the combination of the IC₂₅ of SC-cytarabine or SC-daunorubicin synergizes in the elimination of leukemic cells, with evident induction of apoptosis, while the proliferation of mononuclear cells of bone marrow is not affected. In leukemic mice, the combined administration of SC-daunorubicin or SC-cytarabine promotes the highest survival rate at 40 days; in addition, no autoproliferating cells were detected in the bone marrow of survivors of more than 60 days, evidence of eradication of leukemic cells, but only the bone marrow of mice treated with the SC-daunorubicin combination proliferated in the presence of interleukin-3, which shows that this combination is not toxic to normal bone marrow cells, thus emerging as a possible antileukemic agent.

Response and Toxicity to Cytarabine Therapy in Leukemia and Lymphoma: From Dose Puzzle to Pharmacogenomic Biomarkers

Simple Summary

In this review, the authors propose a crosswise examination of cytarabine-related issues ranging from the spectrum of clinical activity and severe toxicities, through updated cellular pharmacology and drug formulations, to the genetic variants associated with drug-induced phenotypes. Cytarabine (cytosine arabinoside; Ara-C) in multiagent chemotherapy regimens is often used for leukemia or lymphoma treatments, as well as neoplastic meningitis. Chemotherapy regimens can induce a suboptimal clinical outcome in a fraction of patients. The individual variability in clinical response to Leukemia & Lymphoma treatments among patients appears to be associated with intracellular accumulation of Ara-CTP due to genetic variants related to metabolic enzymes. The review provides exhaustive information on the effects of Ara-C-based therapies, the adverse drug reaction will also be provided including bone pain, ocular toxicity (corneal pain, keratoconjunctivitis, and blurred vision), maculopapular rash, and occasional chest pain. Evidence for predicting the response to cytarabine-based treatments will be highlighted, pointing at their significant impact on the routine management of blood cancers.

Abstract

Cytarabine is a pyrimidine nucleoside analog, commonly used in multiagent chemotherapy regimens for the treatment of leukemia and lymphoma, as well as for neoplastic meningitis. Ara-C-based chemotherapy regimens can induce a suboptimal clinical outcome in a fraction of patients. Several studies suggest that the individual variability in clinical response to Leukemia & Lymphoma treatments among patients, underlying either Ara-C mechanism resistance or toxicity, appears to be associated with the intracellular accumulation and retention of Ara-CTP due to genetic variants related to metabolic enzymes. Herein, we reported (a) the latest Pharmacogenomics biomarkers associated with the response to cytarabine and (b) the new drug formulations with optimized pharmacokinetics. The purpose of this review is to provide readers with detailed and comprehensive information on the effects of Ara-C-based therapies, from biological to clinical practice, maintaining high the interest of both researcher and clinical hematologist. This review could help clinicians in predicting the response to cytarabine-based treatments.

MicroRNA-107 promotes apoptosis of acute myelocytic leukemia cells by targeting RAD51

INTRODUCTION

This study aimed to investigate the role of microRNA (miRNA) that affects acute myelocytic leukemia (AML) and its potential molecular mechanism by constructing a miRNA-mRNA interaction network using bioinformatics methods.

MATERIAL AND METHODS

MicroRNA expression data of AML were retrieved from Gene Expression Omnibus (GEO) and analyzed by microarray analysis. Expression levels of miR-107 and RAD51 mRNA were detected by quantitative real time polymerase chain reaction (qRT-PCR). Protein expression of RAD51, pro-apoptotic protein Bax, apoptosis related protein CytC and anti-apoptotic protein Bcl-2 were determined by Western blot. The rate of cell apoptosis was detected by Annexin-V/PI. The predicted targeting relationship between miR-107 and the 3'UTR of RAD51 was first predicted by the online application TargetScan and then verified by dual-luciferase assay.

RESULTS

Acute myelocytic leukemia-associated genes (n = 197) and miRNAs (n = 1701) were retrieved from the database, the interaction network of miRNA-mRNA was constructed and the core position was occupied by RAD51. miR-107 exhibited a regulatory effect on RAD51 in which the mRNA and protein expression of RAD51 were both significantly inhibited by miR-107 mimics in vitro. Additionally, down-regulated expression of miR107 as well as up-regulated expression of RAD51 were detected not only in the plasma of AML patients compared to healthy volunteers, but also in AML cell lines compared to the normal bone marrow stromal cell line. Further study found that increased expression of miR-107 and the consequent down-regulation of RAD51 could aggravate the apoptosis of AML cells in vitro.

CONCLUSIONS

Our present results showed that the crucial role of RAD51 and miR-107 in the apoptosis of AML cells, i.e., miR-107 promotes the apoptosis of AML cells through down-regulating the expression of RAD51.

Targeting multiple signaling pathways: the new approach to acute myeloid leukemia therapy

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults and the second most common form of acute leukemia in children. Despite this, very little improvement in survival rates has been achieved over the past few decades. This is partially due to the heterogeneity of AML and the need for more targeted therapeutics than the traditional cytotoxic chemotherapies that have been a mainstay in therapy for the past 50 years. In the past 20 years, research has been diversifying the approach to treating AML by investigating molecular pathways uniquely relevant to AML cell proliferation and survival. Here we review the development of novel therapeutics in targeting apoptosis, receptor tyrosine kinase (RTK) signaling, hedgehog (HH) pathway, mitochondrial function, DNA repair, and c-Myc signaling. There has been an impressive effort into better understanding the diversity of AML cell characteristics and here we highlight important preclinical studies that have supported therapeutic development and continue to promote new ways to target AML cells. In addition, we describe clinical investigations that have led to FDA approval of new targeted AML therapies and ongoing clinical trials of novel therapies targeting AML survival pathways. We also describe the complexity of targeting leukemia stem cells (LSCs) as an approach to addressing relapse and remission in AML and targetable pathways that are unique to LSC survival. This comprehensive review details what we currently understand about the signaling pathways that support AML cell survival and the exceptional ways in which we disrupt them.

The effects of cytarabine combined with ginsenoside compound K synergistically induce DNA damage in acute myeloid leukemia cells

AML is a kind of hematological malignant tumor that urgently requires different treatment options in order to increase the cure rate and survival rate. Cytarabine (ara-C) is currently the main drug used to treat AML patients and is usually combined with different chemotherapeutic agents. However, due to resistance to ara-C, a new combination is needed to reduce ara-C resistance and improve treatment outcome. As is known to all, ginseng is a traditional Chinese herb; compound K is the principal metabolic product of ginsenoside which also has anti-cancer activity in some cancer cells, while the mechanism is unclear. In our previous study, we found that compound K inhibited AML cell viability and induced apoptosis, and compound K combined with ara-C synergistically induced AML cell proliferation arrest. Thus, we sought to investigate the reason for this by focusing on the mitochondrial dysfunction and DNA damage. In this paper, our results provide a foundation for the clinical evaluation of concomitant administration of compound K and ara-C in order to reduce the resistance to ara-C and improve AML treatment.

Cotargeting of Mitochondrial Complex I and Bcl-2 Shows Antileukemic Activity against Acute Myeloid Leukemia Cells Reliant on Oxidative Phosphorylation

Targeting oxidative phosphorylation (OXPHOS) is a promising strategy to improve treatment outcomes of acute myeloid leukemia (AML) patients. IACS-010759 is a mitochondrial complex I inhibitor that has demonstrated preclinical antileukemic activity and is being tested in Phase I clinical trials. However, complex I deficiency has been reported to inhibit apoptotic cell death through prevention of cytochrome c release. Thus, combining IACS-010759 with a BH3 mimetic may overcome this mechanism of resistance leading to synergistic antileukemic activity against AML. In this study, we show that IACS-010759 and venetoclax synergistically induce apoptosis in OXPHOS-reliant AML cell lines and primary patient samples and cooperatively target leukemia progenitor cells. In a relatively OXPHOS-reliant AML cell line derived xenograft mouse model, IACS-010759 treatment significantly prolonged survival, which was further enhanced by treatment with IACS-010759 in combination with venetoclax. Consistent with our hypothesis, IACS-010759 treatment indeed retained cytochrome c in mitochondria, which was completely abolished by venetoclax, resulting in Bak/Bax- and caspase-dependent apoptosis. Our preclinical data provide a rationale for further development of the combination of IACS-010759 and venetoclax for the treatment of patients with AML.

Safety, pharmacokinetics, and pharmacodynamics of panobinostat in children, adolescents, and young adults with relapsed acute myeloid leukemia

BACKGROUND

Novel therapies are urgently needed for pediatric patients with relapsed acute myeloid leukemia (AML).

METHODS

To determine whether the histone deacetylase inhibitor panobinostat could be safely given in combination with intensive chemotherapy, a phase 1 trial was performed in which 17 pediatric patients with relapsed or refractory AML received panobinostat (10, 15, or 20 mg/m² ) before and in combination with fludarabine and cytarabine.

RESULTS

All dose levels were tolerated, with no dose-limiting toxicities observed at any dose level. Pharmacokinetic studies demonstrated that exposure to panobinostat was proportional to the dose given, with no associations between pharmacokinetic parameters and age, weight, or body surface area. Among the 9 patients who had sufficient (>2%) circulating blasts on which histone acetylation studies could be performed, 7 demonstrated at least 1.5-fold increases in acetylation. Although no patients had a decrease in circulating blasts after single-agent panobinostat, 8 of the 17 patients (47%), including 5 of the 6 patients treated at dose level 3, achieved complete remission. Among the 8 complete responders, 6 (75%) attained negative minimal residual disease status.

CONCLUSIONS

Panobinostat can be safely administered with chemotherapy and results in increased blast histone acetylation. This suggests that it should be further studied in AML.

In Vitro Assessment of the Genotoxic Hazard of Novel Hydroxamic Acid- and Benzamide-Type Histone Deacetylase Inhibitors (HDACi)

Histone deacetylase inhibitors (HDACi) are already approved for the therapy of leukemias. Since they are also emerging candidate compounds for the treatment of non-malignant diseases, HDACi with a wide therapeutic window and low hazard potential are desirable. Here, we investigated a panel of 12 novel hydroxamic acid- and benzamide-type HDACi employing non-malignant V79 hamster cells as toxicology guideline-conform in vitro model. HDACi causing a ≥10-fold preferential cytotoxicity in malignant neuroblastoma over non-malignant V79 cells were selected for further genotoxic hazard analysis, including vorinostat and entinostat for control. All HDACi selected, (i.e., KSK64, TOK77, DDK137 and MPK77) were clastogenic and evoked DNA strand breaks in non-malignant V79 cells as demonstrated by micronucleus and comet assays, histone H2AX foci formation analyses (γH2AX), DNA damage response (DDR) assays as well as employing DNA double-strand break (DSB) repair-defective VC8 hamster cells. Genetic instability induced by hydroxamic acid-type HDACi seems to be independent of bulky DNA adduct formation as concluded from the analysis of nucleotide excision repair (NER) deficient mutants. Summarizing, KSK64 revealed the highest genotoxic hazard and DDR stimulating potential, while TOK77 and MPK77 showed the lowest DNA damaging capacity. Therefore, these compounds are suggested as the most promising novel candidate HDACi for subsequent pre-clinical in vivo studies.

CUDC-907, a novel dual PI3K and HDAC inhibitor, in prostate cancer: Antitumour activity and molecular mechanism of action

Targeting the androgen receptor (AR) signalling pathway remains the main therapeutic option for advanced prostate cancer. However, resistance to AR‐targeting inhibitors represents a great challenge, highlighting the need for new therapies. Activation of the PI3K/AKT pathway and increased expression of histone deacetylases (HDACs) are common aberrations in prostate cancer, suggesting that inhibition of such targets may be a viable therapeutic strategy for this patient population. Previous reports demonstrated that combination of PI3K inhibitors (PI3KIs) with histone deacetylase inhibitors (HDACIs) resulted in synergistic antitumour activities against preclinical models of prostate cancer. In this study, we demonstrate that the novel dual PI3K and HDAC inhibitor CUDC‐907 has promising antitumour activity against prostate cancer cell lines in vitro and castration‐resistant LuCaP 35CR patient‐derived xenograft (PDX) mouse model in vivo. CUDC‐907‐induced apoptosis was partially dependent on Mcl‐1, Bcl‐xL, Bim and c‐Myc. Further, down‐regulation of Wee1, CHK1, RRM1 and RRM2 contributed to CUDC‐907‐induced DNA damage and apoptosis. In the LuCaP 35CR PDX model, treatment with CUDC‐907 resulted in significant inhibition of tumour growth. These findings support the clinical development of CUDC‐907 for the treatment of prostate cancer.

Inhibition of CDK9 by voruciclib synergistically enhances cell death induced by the Bcl-2 selective inhibitor venetoclax in preclinical models of acute myeloid leukemia

Venetoclax, an FDA-approved Bcl-2 selective inhibitor for the treatment of chronic lymphocytic leukemia and acute myeloid leukemia (AML), is tolerated well in elderly patients with AML and has good overall response rates; however, resistance remains a concern. In this study, we show that targeting CDK9 with voruciclib in combination with venetoclax results in synergistic antileukemic activity against AML cell lines and primary patient samples. CDK9 inhibition enhances venetoclax activity through downregulation of Mcl-1 and c-Myc. However, downregulation of Mcl-1 is transient, which necessitates an intermittent treatment schedule to allow for repeated downregulation of Mcl-1. Accordingly, an every other day schedule of the CDK9 inhibitor is effective in vitro and in vivo in enhancing the efficacy of venetoclax. Our preclinical data provide a rationale for an intermittent drug administration schedule for the clinical evaluation of the combination treatment for AML.

Inhibition of Bcl-2 Synergistically Enhances the Antileukemic Activity of Midostaurin and Gilteritinib in Preclinical Models of FLT3-Mutated Acute Myeloid Leukemia

PURPOSE

To investigate the efficacy of the combination of the FLT3 inhibitors midostaurin or gilteritinib with the Bcl-2 inhibitor venetoclax in FLT3-internal tandem duplication (ITD) acute myeloid leukemia (AML) and the underlying molecular mechanism.

EXPERIMENTAL DESIGN

Using both FLT3-ITD cell lines and primary patient samples, Annexin V-FITC/propidium iodide staining and flow cytometry analysis were used to quantify cell death induced by midostaurin or gilteritinib, alone or in combination with venetoclax. Western blot analysis was performed to assess changes in protein expression levels of members of the JAK/STAT, MAPK/ERK, and PI3K/AKT pathways, and members of the Bcl-2 family of proteins. The MV4-11-derived xenograft mouse model was used to assess in vivo efficacy of the combination of gilteritinib and venetoclax. Lentiviral overexpression of Mcl-1 was used to confirm its role in cell death induced by midostaurin or gilteritinib with venetoclax. Changes of Mcl-1 transcript levels were assessed by RT-PCR.

RESULTS

The combination of midostaurin or gilteritinib with venetoclax potently and synergistically induces apoptosis in FLT3-ITD AML cell lines and primary patient samples. The FLT3 inhibitors induced downregulation of Mcl-1, enhancing venetoclax activity. Phosphorylated-ERK expression is induced by venetoclax but abolished by the combination of venetoclax with midostaurin or gilteritinib. Simultaneous downregulation of Mcl-1 by midostaurin or gilteritinib and inhibition of Bcl-2 by venetoclax results in "free" Bim, leading to synergistic induction of apoptosis. In vivo results show that gilteritinib in combination with venetoclax has therapeutic potential.

CONCLUSIONS

Inhibition of Bcl-2 via venetoclax synergistically enhances the efficacy of midostaurin and gilteritinib in FLT3-mutated AML.See related commentary by Perl, p. 6567.

The mTOR inhibitor everolimus overcomes CXCR4-mediated resistance to histone deacetylase inhibitor panobinostat through inhibition of p21 and mitotic regulators

Although having promising anti-myeloma properties, the pan-histone deacetylase inhibitor (HDACi) panobinostat lacks therapeutic activity as a single agent. The aim of the current study was to elucidate the mechanisms underlying multiple myeloma (MM) resistance to panobinostat monotherapy and to define strategies to overcome it. Sensitivity of MM cell lines and primary CD138+ cells from MM patients to panobinostat correlated with reduced expression of the chemokine receptor CXCR4, whereas overexpression of CXCR4 in MM cell lines increased their resistance to panobinostat. Decreased sensitivity to HDACi was associated with reversible G0/G1 cell growth arrest while response was characterized by apoptotic cell death. Analysis of intra-cellular signaling mediators revealed the pro-survival mTOR pathway to be regulated by CXCR4 overexpression. Combining panobinostat with mTOR inhibitor everolimus abrogated the resistance to HDACi and induced synergistic cell death. The combination of panobinostat/everolimus resulted in sustained DNA damage and irreversible suppression of proliferation accompanied by robust apoptosis. Gene expression analysis revealed distinct genetic profiles of single versus combined agent exposure. Whereas panobinostat increased the expression of the cell cycle inhibitor p21, co-treatment with everolimus abrogated the increase in p21 and synergistically downregulated the expression of DNA repair genes and mitotic checkpoint regulators. Importantly, the combination of panobinostat with everolimus effectively targeted CXCR4-expressing resistant MM cells in vivo in the BM niche. In summary, our results uncover the mechanism responsible for the strong synergistic anti-MM activity of dual HDAC and mTOR inhibition and provide the rationale for a novel potential therapeutic approach to treat MM.

Clofarabine Can Replace Anthracyclines and Etoposide in Remission Induction Therapy for Childhood Acute Myeloid Leukemia: The AML08 Multicenter, Randomized Phase III Trial

PURPOSE

To identify effective and less toxic therapy for children with acute myeloid leukemia, we introduced clofarabine into the first course of remission induction to reduce exposure to daunorubicin and etoposide.

PATIENTS AND METHODS

From 2008 through 2017, 285 patients were enrolled at eight centers; 262 were randomly assigned to receive clofarabine and cytarabine (Clo+AraC, n = 129) or high-dose cytarabine, daunorubicin, and etoposide (HD-ADE, n = 133) as induction I. Induction II consisted of low-dose ADE given alone or combined with sorafenib or vorinostat. Consolidation therapy comprised two or three additional courses of chemotherapy or hematopoietic cell transplantation. Genetic abnormalities and the level of minimal residual disease (MRD) at day 22 of initial remission induction determined final risk classification. The primary end point was MRD at day 22.

RESULTS

Complete remission was induced after two courses of therapy in 263 (92.3%) of the 285 patients; induction failures included four early deaths and 15 cases of resistant leukemia. Day 22 MRD was positive in 57 of 121 randomly assigned evaluable patients (47%) who received Clo+AraC and 42 of 121 patients (35%) who received HD-ADE (odds ratio, 1.86; 95% CI, 1.03 to 3.41; P = .04). Despite this result, the 3-year event-free survival rate (52.9% [44.6% to 62.8%] for Clo+AraC v 52.4% [44.0% to 62.4%] for HD-ADE, P = .94) and overall survival rate (74.8% [67.1% to 83.3%] for Clo+AraC v 64.6% [56.2% to 74.2%] for HD-ADE, P = .1) did not differ significantly across the two arms.

CONCLUSION

Our findings suggest that the use of clofarabine with cytarabine during remission induction might reduce the need for anthracycline and etoposide in pediatric patients with acute myeloid leukemia and may reduce rates of cardiomyopathy and treatment-related cancer.

Histone Deacetylase Inhibition with Panobinostat Combined with Intensive Induction Chemotherapy in Older Patients with Acute Myeloid Leukemia: Phase I Study Results

PURPOSE

The histone deacetylase (HDAC) inhibitor panobinostat potentiates anthracycline and cytarabine cytotoxicity in acute myeloid leukemia (AML) cells. We hypothesized that panobinostat prior to and during induction chemotherapy would be tolerable and augment response in patients showing increased histone acetylation.

PATIENTS AND METHODS

Patients received panobinostat 20-60 mg oral daily on days 1, 3, 5, and 8 with daunorubicin 60 mg/m²/day intravenously on days 3 to 5 and cytarabine 100 mg/m²/day intravenously by continuous infusion on days 3 to 9 ("7+3"). Peripheral blood mononuclear cells (PBMCs) were isolated for HDAC expression and histone acetylation changes.

RESULTS

Twenty-five patients ages 60-85 years (median age, 69) were treated. Fifteen patients had de novo AML, six AML with myelodysplasia-related changes, two AML with prior myeloproliferative neoplasm, one therapy-related myeloid neoplasm, and one myelodysplastic syndrome with excess blasts-2. No dose-limiting toxicities occurred in dose escalation cohorts. In dose expansion, six patients received panobinostat at 60 mg and nine patients at 50 mg due to recurrent grade 1 bradycardia at the 60-mg dose. The complete response (CR)/incomplete count recovery (Cri) rate was 32%. Median overall survival was 10 months: 23 months with CR/CRi versus 7.8 months without CR/CRi (log-rank P = 0.02). Median relapse-free survival was 8.2 months. Increased histone acetylation 4 and 24 hours after panobinostat was significantly associated with CR/CRi.

CONCLUSIONS

Panobinostat with "7+3" for older patients with AML was well tolerated. Panobinostat 50 mg on days 1, 3, 5, and 8 starting 2 days prior to "7+3" is recommended for future studies. Panobinostat-induced increases in histone acetylation in PBMCs predicted CR/CRi.

A high-throughput screen indicates gemcitabine and JAK inhibitors may be useful for treating pediatric AML

Improvement in survival has been achieved for children and adolescents with AML but is largely attributed to enhanced supportive care as opposed to the development of better treatment regimens. High risk subtypes continue to have poor outcomes with event free survival rates <40% despite the use of high intensity chemotherapy in combination with hematopoietic stem cell transplant. Here we combine high-throughput screening, intracellular accumulation assays, and in vivo efficacy studies to identify therapeutic strategies for pediatric AML. We report therapeutics not currently used to treat AML, gemcitabine and cabazitaxel, have broad anti-leukemic activity across subtypes and are more effective relative to the AML standard of care, cytarabine, both in vitro and in vivo. JAK inhibitors are selective for acute megakaryoblastic leukemia and significantly prolong survival in multiple preclinical models. Our approach provides advances in the development of treatment strategies for pediatric AML.

Inhibition of Wee1 sensitizes AML cells to ATR inhibitor VE-822-induced DNA damage and apoptosis

Resistance to standard induction therapy and relapse remain the primary challenges for improving therapeutic effects in acute myeloid leukemia (AML); thus, novel therapeutic strategies are urgently required. Ataxia telangiectasia and Rad3-related protein (ATR) is a key regulator of different types of DNA damage, which is crucial for the maintenance of genomic integrity. The ATR-selective inhibitor VE-822 has proper solubility, potency, and pharmacokinetic properties. In this study, we investigated the anti-leukemic effects of VE-822 alone or combined with Wee1-selective inhibitor AZD1775 in AML cells. Our results showed that VE-822 inhibited AML cell proliferation and induced apoptosis in a dose-dependent manner. AZD1775 significantly promoted VE-822-induced inhibition of AML cell proliferation and led to a decreased number of cells in the G2/M phase. VE-822 and AZD1775 decreased the protein levels of ribonucleotide reductase M1 (RRM1) and M2 (RRM2) subunits, key enzymes in the synthesis of deoxyribonucleoside triphosphate, which increased DNA replication stress. VE-822 combined with AZD1775 synergistically induced AML cell apoptosis and led to replication stress and DNA damage in AML cell lines. Our study demonstrated that AZD1775 synergistically promotes VE-822-induced anti-leukemic activity in AML cell lines and provides support for clinical research on VE-822 in combination with AZD1775 for the treatment of AML patients.

PARI (PARPBP) suppresses replication stress-induced myeloid differentiation in leukemia cells

Hyperproliferative cancer cells face increased replication stress, which can result in accumulation of DNA damage. As DNA damage can arrest proliferation, and, in the case of myeloid leukemia, induce differentiation of cancer cells, understanding the mechanisms that regulate the replication stress response is paramount. Here, we show that PARI, a replisome protein involved in regulating DNA repair and replication stress, suppresses differentiation of myeloid leukemia cells. We show that PARI is overexpressed in myeloid leukemia cells, and its knockdown reduces leukemia cell proliferation in vitro and in vivo in xenograft mouse models. PARI depletion enhances replication stress and DNA-damage accumulation, coupled with increased myeloid differentiation. Mechanistically, we show that PARI inhibits activation of the NF-κB pathway, which can initiate p21-mediated differentiation and proliferation arrest. Finally, we show that PARI expression negatively correlates with expression of differentiation markers in clinical myeloid leukemia samples, suggesting that targeting PARI may restore differentiation ability of leukemia cells and antagonize their proliferation.

Antileukemic activity and mechanism of action of the novel PI3K and histone deacetylase dual inhibitor CUDC-907 in acute myeloid leukemia

Induction therapy for patients with acute myeloid leukemia (AML) has remained largely unchanged for over 40 years, while overall survival rates remain unacceptably low, highlighting the need for new therapies. The PI3K/Akt pathway is constitutively active in the majority of patients with AML. Given that histone deacetylase inhibitors have been shown to synergize with PI3K inhibitors in preclinical AML models, we investigated the novel dual-acting PI3K and histone deacetylase inhibitor CUDC-907 in AML cells both in vitro and in vivo. We demonstrated that CUDC-907 induces apoptosis in AML cell lines and primary AML samples and shows in vivo efficacy in an AML cell line-derived xenograft mouse model. CUDC-907-induced apoptosis was partially dependent on Mcl-1, Bim, and c-Myc. CUDC-907 induced DNA damage in AML cells while sparing normal hematopoietic cells. Downregulation of CHK1, Wee1, and RRM1, and induction of DNA damage also contributed to CUDC-907-induced apoptosis of AML cells. In addition, CUDC-907 treatment decreased leukemia progenitor cells in primary AML samples ex vivo, while also sparing normal hematopoietic progenitor cells. These findings support the clinical development of CUDC-907 for the treatment of AML.

Inhibition of XPO1 enhances cell death induced by ABT-199 in acute myeloid leukaemia via Mcl-1

The antiapoptotic Bcl-2 family proteins play critical roles in resistance to chemotherapy in acute myeloid leukaemia (AML). The Bcl-2-selective inhibitor ABT-199 (Venetoclax) shows promising antileukaemic activity against AML, though Mcl-1 limits its antileukaemic activity. XPO1 is a nuclear exporter overexpressed in AML cells and its inhibition decreases Mcl-1 levels in cancer cells. Thus, we hypothesized that the XPO1-selective inhibitor KPT-330 (Selinexor) can synergize with ABT-199 to induce apoptosis in AML cells through down-regulation of Mcl-1. The combination of KPT-330 and ABT-199 was found to synergistically induce apoptosis in AML cell lines and primary patient samples and cooperatively inhibit colony formation capacity of primary AML cells. KPT-330 treatment decreased Mcl-1 protein after apoptosis initiation. However, binding of Bim to Mcl-1 induced by ABT-199 was abrogated by KPT-330 at the same time as apoptosis initiation. KPT-330 treatment increased binding of Bcl-2 to Bim but was overcome by ABT-199 treatment, demonstrating that KPT-330 and ABT-199 reciprocally overcome apoptosis resistance. Mcl-1 knockdown and overexpression confirmed its critical role in the antileukaemic activity of the combination. In summary, KPT-330 treatment, alone and in combination with ABT-199, modulates Mcl-1, which plays an important role in the antileukaemic activity of the combination.

The DEK Oncoprotein Functions in Ovarian Cancer Growth and Survival

DNA damage repair alterations play a critical role in ovarian cancer tumorigenesis. Mechanistic drivers of the DNA damage response consequently present opportunities for therapeutic targeting. The chromatin-binding DEK oncoprotein functions in DNA double-strand break repair. We therefore sought to determine the role of DEK in epithelial ovarian cancer. DEK is overexpressed in both primary epithelial ovarian cancers and ovarian cancer cell lines. To assess the impact of DEK expression levels on cell growth, small interfering RNA and short hairpin RNA approaches were utilized. Decreasing DEK expression in ovarian cancer cell lines slows cell growth and induces apoptosis and DNA damage. The biologic effects of DEK depletion are enhanced with concurrent chemotherapy treatment. The in vitro effects of DEK knockdown are reproduced in vivo, as DEK depletion in a mouse xenograft model results in slower tumor growth and smaller tumors compared to tumors expressing DEK. These findings provide a compelling rationale to target the DEK oncoprotein and its pathways as a therapeutic strategy for treating epithelial ovarian cancer.

Epimutational profile of hematologic malignancies as attractive target for new epigenetic therapies

In recent years, recurrent somatic mutations in epigenetic regulators have been identified in patients with hematological malignancies. Furthermore, chromosomal translocations in which the fusion protein partners are themselves epigenetic regulators or where epigenetic regulators are recruited/targeted by oncogenic fusion proteins have also been described. Evidence has accumulated showing that "epigenetic drugs" are likely to provide clinical benefits in several hematological malignancies, granting their approval for the treatment of myelodysplastic syndromes and cutaneous T-cell lymphomas. A large number of pre-clinical and clinical trials evaluating epigenetic drugs alone or in combination therapies are ongoing. The aim of this review is to provide a comprehensive summary of known epigenetic alterations and of the current use of epigenetic drugs for the treatment of hematological malignancies.

Histone deacetylases 1 and 2 cooperate in regulating BRCA1, CHK1, and RAD51 expression in acute myeloid leukemia cells

Resistance to chemotherapy and a high relapse rate highlight the importance of finding new therapeutic options for the treatment of acute myeloid leukemia (AML). Histone deacetylase (HDAC) inhibitors (HDACIs) are a promising class of drugs for the treatment of AML. HDACIs have limited single-agent clinical activities, but when combined with conventional or investigational drugs they have demonstrated favorable outcomes. Previous studies have shown that decreasing expression of important DNA damage repair proteins enhances standard chemotherapy drugs. In our recent studies, the pan-HDACI panobinostat has been shown to enhance conventional chemotherapy drugs cytarabine and daunorubicin in AML cells by decreasing the expression of BRCA1, CHK1, and RAD51. In this study, we utilized class- and isoform-specific HDACIs and shRNA knockdown of individual HDACs to determine which HDACs are responsible for decreased expression of BRCA1, CHK1, and RAD51 following pan-HDACI treatment in AML cells. We found that inhibition of both HDAC1 and HDAC2 was necessary to decrease the expression of BRCA1, CHK1, and RAD51, enhance cytarabine- or daunorubicin-induced DNA damage and apoptosis, and abrogate cytarabine- or daunorubicin-induced cell cycle checkpoint activation in AML cells. These findings may aid in the development of rationally designed drug combinations for the treatment of AML.

Inhibition of CHK1 enhances cell death induced by the Bcl-2-selective inhibitor ABT-199 in acute myeloid leukemia cells

Resistance to standard chemotherapy agents remains a major obstacle for improving treatment outcomes for acute myeloid leukemia (AML). The Bcl-2-selective inhibitor ABT-199 has demonstrated encouraging preclinical results, drug resistance remains a concern. Mcl-1 has been demonstrated to contribute to ABT-199 resistance, thus combining with therapies that target Mcl-1 could overcome such resistance. In this study, we utilized a CHK1 inhibitor, LY2603618, to decrease Mcl-1 and enhance ABT-199 efficacy. We found that LY2603618 treatment resulted in abolishment of the G2/M cell cycle checkpoint and increased DNA damage, which was partially dependent on CDK activity. LY2603618 treatment resulted in decrease 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. Simultaneous treatment with LY2603618 and ABT-199 resulted in synergistic induction of apoptosis in both AML cell lines and primary patient samples. Our findings provide new insights into overcoming a mechanism of intrinsic ABT-199 resistance in AML cells and support the clinical development of combined ABT-199 and CHK1 inhibition.

Targeting PI3K, mTOR, ERK, and Bcl-2 signaling network shows superior antileukemic activity against AML ex vivo

Acute myeloid leukemia (AML) remains challenging to treat and needs more effective treatments. The PI3K/mTOR pathway is involved in cell survival and has been shown to be constitutively active in 50-80% of AML patients. However, targeting the PI3K/mTOR pathway results in activation of the ERK pathway, which also plays an important role in cell survival. In addition, AML cells often overexpress antiapoptotic Bcl-2 family proteins (e.g., Bcl-2), preventing cell death. Thus, our strategy here is to target the PI3K, mTOR (by VS-5584, a PI3K and mTOR dual inhibitor), ERK (by SCH772984, an ERK-selective inhibitor), and Bcl-2 (by ABT-199, a Bcl-2-selective inhibitor) signaling network to kill AML cells. In this study, we show that while inhibition of PI3K, mTOR, and ERK showed superior induction of cell death compared to inhibition of PI3K and mTOR, the levels of cell death were modest in some AML cell lines and primary patient samples tested. Although simultaneous inhibition of PI3K, mTOR, and ERK caused downregulation of Mcl-1 and upregulation of Bim, immunoprecipitation of Bcl-2 revealed increased binding of Bim to Bcl-2, which was abolished by the addition of ABT-199, suggesting that Bim was bound to Bcl-2 which prevented cell death. Treatment with combined VS-5584, SCH772984, and ABT-199 showed significant increase in cell death in AML cell lines and primary patient samples and significant reduction in AML colony formation in primary patient samples, while there was no significant effect on colony formation of normal human CD34+ hematopoietic progenitor cells. Taken together, our findings show that inhibition of PI3K, mTOR, and ERK synergistically induces cell death in AML cells, and addition of ABT-199 enhances cell death further. Thus, our data support targeting the PI3K, mTOR, ERK, and Bcl-2 signaling network for the treatment of AML.

Orthotopic patient-derived xenografts of paediatric solid tumours

Pediatric solid tumors arise from endodermal, ectodermal, or mesodermal lineages¹. Although the overall survival of children with solid tumors is 75%, that of children with recurrent disease is below 30%². To capture the complexity and diversity of pediatric solid tumors and establish new models of recurrent disease, we developed a protocol to produce orthotopic patient-derived xenografts (O-PDXs) at diagnosis, recurrence, and autopsy. Tumor specimens were received from 168 patients, and 67 O-PDXs were established for 12 types of cancer. The origins of the O-PDX tumors were reflected in their gene-expression profiles and epigenomes. Genomic profiling of the tumors, including detailed clonal analysis, was performed to determine whether the clonal population in the xenograft recapitulated the patient’s tumor. We identified several drug vulnerabilities and showed that the combination of a WEE1 inhibitor (AZD1775), irinotecan, and vincristine can lead to complete response in multiple rhabdomyosarcoma O-PDX tumors in vivo.

Complete molecular remission in relapsed and refractory acute myeloid leukaemia with MLL-AF9 treated with chidamide-based chemotherapy

WHAT IS KNOWN AND OBJECTIVE

The mixed lineage leukaemia (MLL) gene translocations are found in approximately 10% of adults with acute myeloid leukaemia (AML) and are markers of poor prognosis. As the best reported response in relapsed and refractory MLL-rearranged AML is around 40%, reinduction treatment is very challenging for those patients.

CASE DESCRIPTION

We report a case of relapsed and refractory AML with MLL-AF9, who did not respond to FLAG (fludarabine, cytarabine, granulocyte colony stimulating factor) regimen reinduction treatment, but achieved complete response and molecular remission after chidamide-based chemotherapy.

WHAT IS NEW AND CONCLUSION

Chidamide (CS055/HBI-8000) is a new histone deacetylase (HDAC) inhibitor that is clinically active in relapsed and refractory peripheral T-cell lymphomas. To the best of our knowledge, successful reinduction treatment on relapsed MLL-AF9 by chidamide-based regimen has not been previously reported.

E2F1 interactive with BRCA1 pathway induces HCC two different small molecule metabolism or cell cycle regulation via mitochondrion or CD4+T to cytosol

Breast cancer 1 (BRCA1) and E2F transcription factor 1 (E2F1) are related to metabolism and cell cycle regulation. However, the corresponding mechanism is not clear in HCC. High BRCA1 direct pathway was constructed with 11 molecules from E2F1 feedback-interactive network in HCC by GRNInfer based on 39 Pearson mutual positive corelation CC ≥0.25 molecules with E2F1. Integration of GRNInfer with GO, KEGG, BioCarta, GNF_U133A, UNIGENE_EST, Disease, GenMAPP databases by DAVID and MAS 3.0, E2F1 feedback-interactive BRCA1 indirect mitochondrion to cytosol pathway was identified as upstream LAPTM4B activation, feedback UNG, downstream BCAT1-HIST1H2AD-TK1 reflecting protein, and DNA binding with enrichment of small molecule metabolism; The corresponding BRCA1 indirect membrane to cytosol pathway as upstream CCNB2-NUSAP1 activation, feedback TTK-HIST1H2BJ-CENPF, downstream MCM4-TK1 reflecting ATP, and microtubule binding with enrichment of CD4+T-related cell cycle regulation in HCC. Therefore, we propose that E2F1 interactive with BRCA1 pathway induces HCC two different small molecule metabolism or cell cycle regulation via mitochondrion or CD4+T to cytosol. Knowledge analysis demonstrates our E2F1 feedback-interactive BRCA1 pathway wide disease distribution and reflects a novel common one of tumor and cancer.

Inhibition of ATR potentiates the cytotoxic effect of gemcitabine on pancreatic cancer cells through enhancement of DNA damage and abrogation of ribonucleotide reductase induction by gemcitabine

Pancreatic cancer is a highly malignant disease with a dismal prognosis. Gemcitabine (GEM)-based chemotherapy is the first-line treatment for patients with advanced disease, although its efficacy is very limited, mainly due to drug resistance. Ataxia telangiectasia and Rad3-related (ATR) plays a critical role in the DNA damage response (DDR) which has been implicated in GEM resistance. Thus, targeting ATR represents a promising approach to enhance GEM antitumor activity. In the present study, we tested the antitumor activity of AZ20, a novel ATR-selective inhibitor, alone or combined with GEM in 5 pancreatic cancer cell lines. AZ20 treatment of the pancreatic cancer cell lines resulted in growth inhibition, with IC50 values ranging from 0.84 to 2.4 µM, but limited cell death. As expected, treatment of pancreatic cancer cell lines with AZ20 caused decreased phosphorylation of CHK1 (S-345). However, this was accompanied by DNA damage and S and G2/M cell cycle arrest, independent of TP53 gene mutational status. Importantly, combination of AZ20 with GEM resulted in synergistic inhibition of cell growth and cooperative induction of cell death in the pancreatic cancer cell lines. AZ20 significantly increased GEM-induced DNA damage and almost completely abrogated GEM-induced expression of the M2 subunit of ribonucleotide reductase. These findings suggest that inhibition of ATR is a promising strategy to enhance the antitumor activity of GEM for treating pancreatic cancer.