Childhood Acute Lymphoblastic Leukemia Cells Research Articles

Disruption of the Hippo pathway promotes the proliferation of childhood acute lymphoblastic leukemia cells, inhibits apoptosis and chemosensitivity

ABSTRACT Background Despite advancements in chemotherapy and stem cell transplantation, the recurrence and chemoresistance of childhood acute lymphoblastic leukemia (cALL) remain a significant challenge, thus indicating the need for novel therapeutic targets. Research design and methods The protein levels of YAP1, p-YAP1, TAZ, and Cyr61 of cALL patients and healthy volunteers were measured by western blot analysis. Then the leukemic cell line SUP-B15 was transfected with sh-YAP1 and pcDNA3.1-YAP1 to knockdown or overexpress YAP1. The viability, chemosensitivity, apoptosis, migration, and invasion of SUP-B15 cells were determined by MTT, flow cytometry, and Transwell assay. Results The cALL patients had higher YAP1, TAZ, and Cyr61 protein expression and lower p-YAP1 protein expression in bone marrow tissues compared with healthy volunteers (p < 0.01). In SUP-B15 cells, YAP1 knockdown upregulated p-YAP1 protein expression (p < 0.01) and downregulated TAZ and Cyr61 protein expression (p < 0.01). In addition, knocking down YAP1 significantly inhibited cell viability, migration, and invasion, and induced apoptosis (p < 0.01). YAP1 knockdown also reduced the IC50 value following treatment with vincristine, daunorubicin, cyclophosphamide, and dexamethasone (p < 0.05). Conclusions Disruption of the Hippo pathway attenuates the development of cALL by promoting cell proliferation while suppressing apoptosis and drug sensitivity.

Effect of LncRNA GATA3-AS1 Targeting MiR-515-5p on Cell Proliferation and Apoptosis in Childhood Acute Lymphoblastic Leukemia Cells

To investigate the effects of long non-coding RNA (lncRNA) GATA3 antisense RNA 1 (GATA3-AS1) targeting miR-515-5p on the proliferation and apoptosis of childhood acute lymphoblastic leukemia (ALL) cells. RT-qPCR was used to determine the expression of GATA3-AS1 and miR-515-5p in the plasma of controls and ALL children. Human ALL cells Jurkat were divided into si-GATA3-AS1, si-NC, miR-NC, miR-515-5p, si-GATA3-AS1+anti-miR-NC and si-GATA3-AS1+anti-miR-515-5p groups. CCK-8 assay was used to detect the cell proliferation, and flow cytometry was used to detect the cell apoptosis. The targeting relationship between GATA3-AS1 and miR-515-5p was determined by dual-luciferase reporter assay. The expression level of GATA3-AS1 in the plasma of ALL children was significantly higher than that of controls (P <0.001), while the expression level of miR-515-5p was significantly lower than that of controls (P <0.001). Compared with the si-NC group, the cell inhibition rate, apoptosis rate, and miR-515-5p expression level in si-GATA3-AS1 group were significantly increased (P <0.001). Compared with the miR-NC group, the cell inhibition rate and apoptosis rate in miR-515-5p group were significantly increased (P <0.001). GATA3-AS1 could directly and specifically bind to miR-515-5p. Compared with the si-GATA3-AS1+anti-miR-NC group, the cell inhibition rate and apoptosis rate in si-GATA3-AS1+anti-miR-515-5p group were significantly decreased (P <0.001). Down-regulation of GATA3-AS1 can inhibit proliferation and induce apoptosis of childhood ALL cells by targeting up-regulation of miR-515-5p expression.

Integrative multi-omics and drug response profiling of childhood acute lymphoblastic leukemia cell lines.

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Although standard-of-care chemotherapeutics are sufficient for most ALL cases, there are subsets of patients with poor response who relapse in disease. The biology underlying differences between subtypes and their response to therapy has only partially been explained by genetic and transcriptomic profiling. Here, we perform comprehensive multi-omic analyses of 49 readily available childhood ALL cell lines, using proteomics, transcriptomics, and pharmacoproteomic characterization. We connect the molecular phenotypes with drug responses to 528 oncology drugs, identifying drug correlations as well as lineage-dependent correlations. We also identify the diacylglycerol-analog bryostatin-1 as a therapeutic candidate in the MEF2D-HNRNPUL1 fusion high-risk subtype, for which this drug activates pro-apoptotic ERK signaling associated with molecular mediators of pre-B cell negative selection. Our data is the foundation for the interactive online Functional Omics Resource of ALL (FORALL) with navigable proteomics, transcriptomics, and drug sensitivity profiles at https://proteomics.se/forall.

High Expression of BCL11A Predicts Poor Prognosis for Childhood MLL-r ALL.

BackgroundDespite much improvement in the treatment for acute lymphoblastic leukemia (ALL), childhood ALLs with MLL-rearrangement (MLL-r) still have inferior dismal prognosis. Thus, defining mechanisms underlying MLL-r ALL maintenance is critical for developing effective therapy.MethodsGSE13159 and GSE28497 were selected via the Oncomine website. Differentially expressed genes (DEGs) between MLL-r ALLs and normal samples were identified by R software. Next, functional enrichment analysis of these DEGs were carried out by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Set Enrichment Analysis (GSEA), and Search Tool for the Retrieval of Interacting Genes/Proteins (STRING). Then, the key hub genes and modules were identified by Weighted Gene Co-expression Network Analysis (WGCNA). Therapeutically Applicable Research to Generate Effective Treatments (TARGET) ALL (Phase I) of UCSC Xena analysis, qPCR, and Kaplan-Meier analysis were conducted for validating the expression of key hub genes from bone marrow cells of childhood ALL patients or ALL cell lines.ResultsA total of 1,045 DEGs were identified from GSE13159 and GSE28497. Through GO, KEGG, GSEA, and STRING analysis, we demonstrated that MLL-r ALLs were upregulating “nucleosome assembly” and “B cell receptor signal pathway” genes or proteins. WGCNA analysis found 18 gene modules using hierarchical clustering between MLL-r ALLs and normal. The Venn diagram was used to filter the 98 hub genes found in the key module with the 1,045 DEGs. We identified 18 hub genes from this process, 9 of which were found to be correlated with MLL-r status, using the UCSC Xena analysis. By using qPCR, we validated these 9 hub key genes to be upregulated in the MLL-r ALLs (RS4;11 and SEM) compared to the non-MLL-r ALL (RCH-ACV) cell lines. Three of these genes, BCL11A, GLT8D1 and NCBP2, were shown to be increased in MLL-r ALL patient bone marrows compared to the non-MLL-r ALL patient. Finally, Kaplan–Meier analysis indicated that childhood ALL patients with high BCL11A expression had significantly poor overall survival.ConclusionThese findings suggest that upregulated BCL11A gene expression in childhood ALLs may lead to MLL-r ALL development and BCL11A represents a new potential therapeutic target for childhood MLL-r ALL.

NF-κB signaling pathway promotes proliferation and inhibits apoptosis of childhood acute lymphoblastic leukemia cells via regulating CRIM1.

NF-κB signaling pathway promotes proliferation and inhibits apoptosis of childhood acute lymphoblastic leukemia cells via regulating CRIM1.

Thiol-Reactive Star Polymers Functionalized with Short Ethoxy-Containing Moieties Exhibit Enhanced Uptake in Acute Lymphoblastic Leukemia Cells.

PurposeDirecting nanoparticles to cancer cells without using antibodies is of great interest. Subtle changes to the surface chemistry of nanoparticles can significantly affect their biological fate, including their propensity to associate with different cell populations. For instance, nanoparticles functionalized with thiol-reactive groups can potentially enhance association with cells that over-express cell-surface thiol groups. The potential of such an approach for enhancing drug delivery for childhood acute lymphoblastic leukemia (ALL) cells has not been investigated. Herein, we investigate the impact of thiol-reactive star polymers on the cellular association and the mechanisms of uptake of the nanoparticles.MethodsWe prepared fluorescently labeled star polymers functionalized with an mPEG brush corona and pyridyl disulfide to examine how reactivity to exofacial thiols impacts cellular association with ALL cells. We also studied how variations to the mPEG brush composition could potentially be used as a secondary method for controlling the extent of cell association. Specifically, we examined how the inclusion of shorter diethylene glycol brush moieties into the nanoparticle corona could be used to further influence cell association.ResultsStar polymers incorporating both thiol-reactive and diethylene glycol brush moieties exhibited the highest cellular association, followed by those functionalized solely with thiol reactive groups compared to control nanoparticles in T and B pediatric ALL patient-derived xenografts harvested from the spleens and bone marrow of immunodeficient mice. Transfection of cells with an early endosomal marker and imaging with correlative light and electron microscopy confirmed cellular uptake. Endocytosis inhibitors revealed dynamin-dependent clathrin-mediated endocytosis as the main uptake pathway for all the star polymers.ConclusionThiol-reactive star polymers having an mPEG brush corona that includes a proportion of diethylene glycol brush moieties represent a potential strategy for improved leukemia cell delivery.

Effects of MiR-221-Mediated Wnt/β- Catenin Signaling Pathway on Biological Activity of Childhood Acute Lymphoblastic Leukemia Cells

To study the effects of miR-221 on the biological activity of childhood acute lymphoblastic leukemia cells and its mechanism. Bone marrow mononuclear cells (BMNC) were isolated from bone marrow samples of ALL children diagnosed in our hospital from May 2018 to November 2018. The cells were divided into control group, miR-221-NC group and miR-221 group. After transfection according to the instructions of Lipofectamine 2000 kit, the levels of miR-221 in each group were detected by RT-PCR. Flow cytometry was used to detect the effects of miR-221 on cell cycle and apoptosis. Transwell assay was used to detect cell migration and invasion. Western blot was used to detect the effects of miR-221 on proliferating cell nuclear antigen (PCNA), Caspase 3, Cyclin D1 and MMP-9 proteins in BMNC. Luciferase reporter gene assay was used to detect the targeting relationship between miR-221 and Wnt gene. The expression level of miR-221 in the miR-221 group was significantly higher than that in the control group and the miR-221-NC group (P＜0.05). MTT assay showed that, after transfection for 2, 3, 4 and 5 days, the cell proliferation level in miR-221 group was significantly lower than that in the control group and the miR-221-NC group (P＜0.05). The cell ratio of G0/G1 phase was (73.25±8.1)% in the miR-221 group, which was significantly higher than that in the control group and the miR-221-NC group (P＜0.05); moreover, the cell ratio of S phase in the miR-221 group was (12.37±1.6)%，which was significantly lower than that in the control group and the miR-221-NC group (P＜0.05). The percentage of apoptotic cells in the miR-221 group was (24.68±3.87)%, which was significantly higher than that in the control group and the miR-221-NC group (P＜0.05). Transwell cell invasion experiment showed that the number of invasive cells in the miR-221 group was 23.42±3.62, which was significantly lower than that in the control group and the miR-221-NC group (P＜0.05). Transwell cell migration assay showed that the number of migrating cells in the miR-221 group was 34.86±5.32, which was significantly lower than that in the control group and the miR-221-NC group (P＜0.05). The relative level of PCNA, Cyclin D1 and MMP-9 in the miR-221 group was 0.26±0.03, 0.17±3.61 and 0.14±0.02, respectively, which was significantly lower than those in the control group and the miR-221-NC group (P＜0.05), while the relative level of Caspase-3 in the miR-221 group was 0.37±0.05, which was significantly higher than that in the control group and the miR-221-NC group (P＜0.05). Luciferase reporter assay showed that the activity of luciferase in Wnt wild type plasmid was significantly inhibited by miR-221 (P＜0.05). miR-221 can inhibit the proliferation, migration and invasion of BMNC, moreover can promote cell apoptosis, which may be related with the inhibition of Wnt/β- catenin signaling pathway.

Establishment and characterization of a novel childhood acute lymphoblastic leukemia cell line, HXEX-ALL1, with chromosome 9p and 17p deletions

BackgroundAlthough contemporary chemotherapy has improved the cure rate of childhood acute lymphoblastic leukemia (ALL) to nearly 90%, relapsed/refractory ALL is still a leading cause of tumor-related death in children. To clarify the underlying mechanisms of relapsed/refractory childhood ALL, researchers urgently need to establish novel cell models from patients with relapsed ALL after treatment with contemporary chemotherapy.MethodsCell culture technique was used to establish the HXEX-ALL1 cell line from primary B cell precursor ALL (BCP-ALL) cells. Molecular and cellular biological techniques including flow cytometry, polymerase chain reaction (PCR), short tandem repeat (STR) analysis, conventional cytogenetics, and chromosomal microarray analysis (CMA) were used to characterize the HXEX-ALL1 cell line. Nude mice were used for xenograft studies.ResultsA stable ALL cell line, HXEX-ALL1, derived from a 6-year-old boy of Han nationality with BCP-ALL at the second relapse, was established and maintained in culture for more than 18 months. The HXEX-ALL1 cell line was authenticated as being derived from primary leukemia cells based on morphologic, immunophenotypic, cytogenetic and STR analyses and demonstrated tumorigenicity in nude mice. WGS data showed that there were 27,006 novel single nucleotide polymorphisms (SNPs) and 193,951 novel insertion/deletions (InDels) in HXEX-ALL1 cells. Compared with the other BCP-ALL cell lines in use, the HXEX-ALL1 cells have a special karyotype represented by trisomy 8 and 9p and 17p deletions with a multidrug resistance phenotype, especially highly resistant to asparaginase.ConclusionsThe HXEX-ALL1 cell line may prove to be a useful model for the study of relapsed/refractory childhood ALL, particularly for the researches on asparaginase resistance.

AICAr suppresses cell proliferation by inducing NTP and dNTP pool imbalances in acute lymphoblastic leukemia cells.

It has been shown that 5-amino-4-imidazolecarboxamide riboside (AICAr) can inhibit cell proliferation and induce apoptosis in childhood acute lymphoblastic leukemia (ALL) cells. Although AICAr could regulate cellular energy metabolism by activating AMPK, the cytotoxic mechanisms of AICAr are still unclear. Here, we knocked out TP53 or PRKAA1 gene (encoding AMPKα1) in NALM-6 and Reh cells by using the clustered regularly interspaced short palindromic repeats/Cas9 system and found that AICAr-induced proliferation inhibition was independent of AMPK activation but dependent on p53. Liquid chromatography-mass spectrometry analysis of nucleotide metabolites indicated that AICAr caused an increase in adenosine triphosphate, deoxyadenosine triphosphate, and deoxyguanosine triphosphate levels by up-regulating purine biosynthesis, while AICAr led to a decrease in cytidine triphosphate, uridine triphosphate, deoxycytidine triphosphate, and deoxythymidine triphosphate levels because of reduced phosphoribosyl pyrophosphate production, which consequently impaired the pyrimidine biosynthesis. Ribonucleoside triphosphate (NTP) pool imbalances suppressed the rRNA transcription efficiency. Furthermore, deoxy-ribonucleoside triphosphate (dNTP) pool imbalances induced DNA replication stress and DNA double-strand breaks, followed by cell cycle arrest and apoptosis in ALL cells. Exogenous uridine could rebalance the NTP and dNTP pools by supplementing pyrimidine and then attenuate AICAr-induced cytotoxicity. Our data indicate that RNA transcription inhibition and DNA replication stress induced by NTP and dNTP pool imbalances might play a key role in AICAr-mediated cytotoxic effects on ALL cells, suggesting a potential clinical application of AICAr in future ALL therapy.-Du, L., Yang, F., Fang, H., Sun, H., Chen, Y., Xu, Y., Li, H., Zheng, L., Zhou, B.-B. S. AICAr suppresses cell proliferation by inducing NTP and dNTP pool imbalances in acute lymphoblastic leukemia cells.

G9a Correlates with VLA-4 Integrin and Influences the Migration of Childhood Acute Lymphoblastic Leukemia Cells.

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer. As ALL progresses, leukemic cells cross the endothelial barrier and infiltrate other tissues. Epigenetic enzymes represent novel therapeutic targets in hematological malignancies, and might contribute to cells’ capacity to migrate across physical barriers. Although many molecules drive this process, the role of the nucleus and its components remain unclear. We report here, for the first time, that the expression of G9a (a histone methyltransferase related with gene silencing) correlates with the expression of the integrin subunit α4 in children with ALL. We have demonstrated that G9a depletion or its inhibition with BIX01294 abrogated the ability of ALL cells to migrate through an endothelial monolayer. Moreover, G9a-depleted and BIX01294-treated cells presented bigger nuclei and more adherent phenotype than control cells on endothelial monolayers. Blocking G9a did not affect the cell cytoskeleton or integrin expression of ALL cell lines, and only its depletion reduced slightly F-actin polymerization. Similarly to the transendothelial migration, G9a inhibition impaired the cell migration induced by the integrin VLA-4 (α4β1) of primary cells and ALL cell lines through narrow spaces in vitro. Our results suggest a cellular connection between G9a and VLA-4, which underlies novel functions of G9a during ALL cell migration.

Synergistic action of dual IGF1/R and MEK inhibition sensitizes childhood acute lymphoblastic leukemia (ALL) cells to cytotoxic agents and involves downregulation of STAT6 and PDAP1

Heterogeneous upregulation of multiple prosurvival pathways underlies resistance to damage-induced apoptosis in acute lymphoblastic leukemia (ALL) cells despite normal p53 responses. Here, we show that the dual combination of insulin-like growth factor 1 (IGF1)/IGF1 receptor (IGF1/R) and mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK) inhibition using AG1024 + U0126 can sensitize apoptosis-resistant ALL cells to ionizing radiation-induced DNA damage irrespective of effect of single pathway inhibition in vitro. This AG1024 + U0126 combination also significantly potentiates the ability of the core chemotherapy compounds vincristine, dexamethasone, and daunorubicin to kill ALL cells in vitro. Evidence of the synergistic action of AG1024 + U0126 in samples with variable basal levels of phosphorylated IGF1/Rβ and ERK1/2 suggested additional targets of this drug combination. Consistent with this, gene expression profiling identified 32 "synergy genes" differentially targeted by IGF1/R + MEK inhibition and, among these, Signal transducer and activator of transcription 6 (STAT6) and platelet-derived growth factor-associated protein 1 (PDAP1) were the most differentially downregulated cluster. Pearson correlation analysesrevealed that STAT6 and PDAP1 display significant expression codependency and a common expression pattern linked with other key "synergy" genes, supporting their predicted role in an STAT6-ERK-nuclear factor kappa beta (NF-κB) network. Knockdown studies revealed that loss of STAT6, but not PDAP1, impinges on the cell cycle, causing reduced numbers of viable cells. In combination with daunorubicin, STAT6 loss has an additive effect on cell killing, whereas PDAP1 loss is synergistic, indicating an important role of PDAP1 in the cellular response to this anthracycline. Inhibition of STAT6 or PDAP1 may therefore represent a potential novel therapeutic strategy for resistant ALL by enhancing sensitivity to chemotherapy.

Mometasone furoate inhibits growth of acute leukemia cells in childhood by regulating PI3K signaling pathway

ABSTRACTObjectives: Acute lymphoblastic leukemia (ALL) is the most common cancer before the age of 15 years, seriously endangering the health of children. The main treatment for Childhood ALL was pharmacotherapy. But these drugs have many side effects and some of them could develop drug resistance quickly. Mometasone furoate (MF) is an efficient glucocorticoid for topical treatment of inflammation on the skin, lung and nose.Methods: In this study, we investigated whether the MF had effects on ALL cells proliferation and migration.Results: The CCK-8 proliferation test showed that the cell viability was the lowest at 25 nM MF treatment and the increased OD value was time-dependent. In transwell assay, the number of CCRF-CEM cells was reduced in MF treated group. We found the expression of anti-apoptotic protein bcl-2 decreased the expression of pro-apoptotic protein caspase3 and bax increased in CCRF-CEM cell line treated with MF. The expression of p-AKT, p-mTOR, p70S6 K, vascular endothelial growth factor and CyclinD1 were decreased in MF treated group.Conclusion: This study reveals that MF can inhibit proliferation and invasion/migration and induce apoptosis in Childhood ALL cells, which may be regulated by Phosphatidylinositol 3-kinase signaling pathway. These results suggest MF may be a potential new drug target for clinical ALL treatment.

Expression and significance of microRNA-195 and Bcl-2 mRNA in the childhood acute lymphoblastic leukemia cells

Objective To investigate the expression and significance of microRNA-195 (miR-195) and Bcl-2 in different type of childhood acute lymphoblastic leukemia(ALL) cells. Methods A total of 110 patients diagnosed as ALL from the Pediatrics Department and Outpatient Department of the First Affiliated Hospital of Zhengzhou University from July 2010 to December 2016 were recruited.The patients included newly diagnosed group, remi-ssion group and relapse group in which the newly diagnosed group was divided into standard risk(SR) group, interme-diate risk (IR) group and high risk (HR) group.And another 14 gender-and age-matched children received bone orthopaedic surgery who excluded tumor and blood system diseases in the same hospital were recruited as control group during the same period.Bone marrow samples of 2-5 mL were drawn from all the subjects.The samples of miR-195 and the expression of Bcl-2 mRNA were detected by using quantitative real time polymerase chain reaction, while the expression of Bcl-2 protein was also detected by using Western blot. Results MiR-195 expression was lower in the newly diagnosis and relapse ALL children(SR: 1.25±0.15; IR: 1.63±0.54; HR: 0.78±0.35; relapse: 0.46±0.18), compared with the control group, and there were statistically significant differences (t=42.44, 28.63, 41.35, 42.65, all P=0.000), but the expression of Bcl-2 mRNA was higher in the newly diagnosis and relapse ALL children than that in the control group (SR: 2.56±0.91; IR: 4.52±0.43; HR: 5.49±1.28; relapse: 5.32±1.15), which had statistically significant differences (t=3.58, 9.86, 10.12, 8.81, all P=0.000). With the rising of the criticality of ALL, the expression of miR-195 reduced gradually, and the expression of Bcl-2 mRNA increased step by step.Determining the protein of Bcl-2 detected by Western blot showed the same result. Conclusions The lower expression of miR-195 and the higher expression of Bcl-2 may be a marker to distinguish the risk factors of ALL, which may be important for the diagnosis and the determination of the degree of risk for the ALL children. Key words: Acute lymphoblastic leukemia; microRNA-195; Bcl-2

Proteomic changes in a childhood acute lymphoblastic leukemia cell line during the adaptation to vincristine

IntroductionRelapse occurs in approximately 20% of Mexican patients with childhood acute lymphoblastic leukemia (ALL). In this group, chemoresistance may be one of the biggest challenges. An overview of complex cellular processes like drug tolerance can be achieved with proteomic studies. MethodsThe B-lineage pediatric ALL cell line CCRF-SB was gradually exposed to the chemotherapeutic vincristine until proliferation was observed at 6nM, control cells were cultured in the absence of vincristine. The proteome from each group was analyzed by nanoHPLC coupled to an ESI-ion trap mass spectrometer. The identified proteins were grouped into overrepresented functional categories with the PANTHER classification system. ResultsWe found 135 proteins exclusively expressed in the presence of vincristine. The most represented functional categories were: Toll receptor signaling pathway, Ras Pathway, B and T cell activation, CCKR signaling map, cytokine-mediated signaling pathway, and oxidative phosphorylation. ConclusionsOur study indicates that signal transduction and mitochondrial ATP production are essential during adaptation of leukemic cells to vincristine, these processes represent potential therapeutic targets.

Proteomic changes in a childhood acute lymphoblastic leukemia cell line during the adaptation to vincristine

Proteomic changes in a childhood acute lymphoblastic leukemia cell line during the adaptation to vincristine

The combination effects of bendamustine with antimetabolites against childhood acute lymphoblastic leukemia cells.

Bendamustine combined with other drugs is clinically efficacious for some adult lymphoid malignancies, but to date there are no reports of the use of such combinatorial approaches in pediatric patients. We investigated the in vitro activity of bendamustine combined with other antimetabolite drugs on B cell precursor acute lymphoblastic leukemia (BCP-ALL) cell lines established from pediatric patients with refractory or relapsed ALL. We also developed a mathematically drown improved isobologram method to assess the data objectively. Three BCP-ALL cell lines; YCUB-2, YCUB-5, and YCUB-6, were simultaneously exposed to various concentrations of bendamustine and cladribine, cytarabine, fludarabine, or clofarabine. Cell growth inhibition was determined using the WST-8 assay. Combinatorial effects were estimated using our improved isobologram method with IC80 (drug concentration corresponding to 80 % of maximum inhibition). Bendamustine alone inhibited ALL cell growth with mean IC80 values of 11.30-18.90 μg/ml. Combinations of bendamustine with other drugs produced the following effects: (1) cladribine; synergistic-to-additive on all cell lines; (2) cytarabine; synergistic-to-additive on YCUB-5 and YCUB-6, and synergistic-to-antagonistic on YCUB-2; (3) fludarabine; additive-to-antagonistic on YCUB-5, and synergistic-to-antagonistic on YCUB-2 and YCUB-6; (4) clofarabine; additive-to-antagonistic on all cell lines. Flow cytometric analysis also showed the combination effects of bendamustine and cladribine. Bendamustine/cladribine or bendamustine/cytarabine may thus represent a promising combination for salvage treatment in childhood ALL.

Pharmacological inhibition of fatty-acid oxidation synergistically enhances the effect of l-asparaginase in childhood ALL cells.

l-asparaginase (ASNase), a key component in the treatment of childhood acute lymphoblastic leukemia (ALL), hydrolyzes plasma asparagine and glutamine and thereby disturbs metabolic homeostasis of leukemic cells. The efficacy of such therapeutic strategy will depend on the capacity of cancer cells to adapt to the metabolic challenge, which could relate to the activation of compensatory metabolic routes. Therefore, we studied the impact of ASNase on the main metabolic pathways in leukemic cells. Treating leukemic cells with ASNase increased fatty-acid oxidation (FAO) and cell respiration and inhibited glycolysis. FAO, together with the decrease in protein translation and pyrimidine synthesis, was positively regulated through inhibition of the RagB-mTORC1 pathway, whereas the effect on glycolysis was RagB-mTORC1 independent. As FAO has been suggested to have a pro-survival function in leukemic cells, we tested its contribution to cell survival following ASNase treatment. Pharmacological inhibition of FAO significantly increased the sensitivity of ALL cells to ASNase. Moreover, constitutive activation of the mammalian target of rapamycin pathway increased apoptosis in leukemic cells treated with ASNase, but did not increase FAO. Our study uncovers a novel therapeutic option based on the combination of ASNase and FAO inhibitors.

Activated Fibroblasts Protect Acute Myeloid Leukemia Cells from Chemotherapy

Introduction: It has become clear that cancer is not only just a disease of the genes, but the tumor microenvironment (TME) plays an important role in cancer progression (Borriello L & DeClerck YA, 2014). In leukemia, the bone marrow plays a special role in environment-mediated drug resistance as it is not only a sanctuary protecting tumor cells from cytotoxic drugs, but also a source of many stromal cells that colonize primary tumors and contribute to the pre-metastatic niche (Borriello L & DeClerck YA, 2014; Meads MB, et al, 2008). As we all know, there exists two distinct BM niches in this significant microenvironment: ‘osteoblastic (endosteal)’ and ‘vascular’ niches (Tabe Y & Konopleva M, 2014; Konopleva M, et al, 2009). Besides these two, scholars transferred to focus on the stromal in bone marrow，which may have importance effects on leukemic cells (Wu S, et al, 2005; Campana D, et al, 2005). Shriram V. Nath et al. found that there was a negative correlation between reticulin fiber density (RFD) at diagnosis in childhood ALL and white blood cell count in peripheral blood. Similarly, there was a negative correlation between RFD and the percentage of blast cells in blood. They speculated fiber in the bone marrow leading to poor prognosis in acute lymphoblastic leukemia (ALL) via anchoring leukemia cells in bone marrow stromal (Nath SV, et al. 2011). But the role of fibers and its mainly producing cells fibroblasts has not been previously studied in acute myeloid leukemia (AML). Therefore, we retrospectively investigate the bone marrow biopsies of primary AML patients, to analyze the relationship between the RFD and prognosis in adult AML, and to identify and quantitative analyze protective effects of the fibroblasts on leukemia cells from chemotherapy in vitro.Methods: Makers of activated fibroblasts were stained by immunohistochemistry on bone marrow biopsies; The RFD were evaluated based on the grid point method of computer; Obtained activated fibroblasts by induced BM-MSC of primary AML with human recombinant TGFβ1.(4) Analyzed protective effects of activated fibroblasts by co-cultured with leukemia cells such as THP-1/K562, futher explored the mechanism via SB431542, a specific inhibitor of TGFβ signaling pathway.Result:RFD in primary AML was significant higher than control. Patients with higher RFD indicated poorer prognosis; However, collagenI coated plates showed no effects on survival rate of the leukemic cells. Here, we demonstrated that the general makers of activated fibroblasts: FSP1, α-SMA and FAP in primary AML were significant higher than control, implied that there existed amount of activated fibroblasts in patients; Activated fibroblast protect both THP-1 and K562 from apoptosis with treatment of Ara-c, and arrested them in phase of G0/G1. Moreover, this protect effects of activated fibroblast will be cancelled with SB431542.Conclusion:Activated fibroblasts and fibrous tissue were both proliferated abnormally in primary AML, and the later was significantly associated with relapse-free survival and overall survival of patients, indicating that RFD could be used as an important factor of poor prognosis and should guide clinical intervention. In vitro induced activated fibroblasts could be able to protect leukemia cells from chemotherapy. The possible mechanisms might be that the soluble cytokines TGFβ1, but not collagen I, which were secreted by activated fibroblasts, contributed to leukemia protection. In addition to this, activated fibroblasts could also change cell cycle of tumor cells, make them more arrested in G0/G1 phase, thus decreased the their chemotherapy sensitivity. DisclosuresNo relevant conflicts of interest to declare.

Zebularine induces chemosensitization to methotrexate and efficiently decreases AhR gene methylation in childhood acute lymphoblastic leukemia cells

Acute lymphoblastic leukemia (ALL) is the most common hematologic malignancy in childhood. Despite the advances in treatment, about 20% of patients relapse and/or die, indicating the need for different therapies for this group. Zebularine (ZB) is a potent DNA methyltransferase (DNMT) inhibitor and has been associated with gene demethylation and enhancement of tumor chemosensitivity. This study aimed to evaluate the effects of ZB, alone or combined with chemotherapeutics (methotrexate and vincristine), on childhood ALL cell lines. Cell proliferation, apoptosis, and clonogenic capacity were studied in Jurkat and ReH cell lines. Bisulfite modification, followed by methylation-specific PCR was carried out to evaluate aryl hydrocarbon receptor (AhR) methylation status. Gene expression of DNMT1, DNMT3a, DNMT3b, and AhR was assessed using qRT-PCR. Both cell cultures were sensitive to ZB, showing a dose-dependent and time-dependent response (P<0.05). ZB induced apoptosis and decreased clonogenic capacity in both cell lines. Combination with methotrexate resulted in a strong synergistic effect, whereas combination with vincristine led to an antagonistic response in both cell lines. ZB treatment decreased gene expression of the three DNMTs and induced AhR gene promoter demethylation and its re-expression. These results indicate that ZB may be a promising drug for the adjuvant treatment of ALL, mainly when combined with methotrexate.

Smac Mimetic-Mediated Sensitization Of Childhood ALL Cells For Drug-Induced Apoptosis Independent Of TNFα and NFκB Signaling Pathways

Targeting inhibitor of apoptosis proteins (IAPs) using small molecular Smac mimetics (SM) has been shown to offer a novel promising treatment strategy for resistant malignant diseases including childhood acute lymphoblastic leukemia (ALL). The effect of SM alone has been shown to be associated with endogenous TNFα expression, therefore tumor cells can be classified into sensitive or resistant against apoptosis induction by SM alone. In SM sensitive tumor cells the effect of SM has been shown to be mediated mainly by degradation of cellular IAP (cIAP) and activation of TNFα and NFκB signaling pathways but not inhibition of XIAP.We show here, that sensitivity of ALL cells to SM alone (as well as TNFα expression) is highly variable. Nevertheless even in ALL cells resistant against SM alone, treatment with SM resulted in significant sensitization for drugs used within standard induction therapy for childhood ALL. Sensitization for drug-induced apoptosis by SM was not only mediated by activation of the intrinsic (cleavage of caspase 9) but also extrinsic apoptosis pathway (cleavage of caspase 8). Surprisingly, SM-induced cIAP degradation alone was not sufficient for caspase 8 activation and apoptosis induction. Consistently, SM-mediated sensitization for drug-induced apoptosis was independent of TNFα and NFκB signaling pathways. We demonstrate that caspase 8 activation by combined treatment with SM and cytostatic drugs is blocked by inhibition of caspase 3 and caspase 9 and therefore occurs downstream of intrinsic apoptosis pathway activation.In conclusion, our data argue for a model comprising inhibition of XIAP-mediated blockade of caspase 3/9 as the central effect of SM in chemo-sensitization of childhood ALL cells resistant against SM-alone. Disclosures:No relevant conflicts of interest to declare.