Acute Lymphoid Leukemia Cell Lines Research Articles

Cathepsin G Is Expressed By B Cell Acute Lymphoblastic Leukemia and Is an Effective Immunotherapeutic Target

The azurophil granule proteases neutrophil elastase (NE) and proteinase 3 (P3) have been established as effective immunotherapeutic targets in hematological malignancies. Expression of PR1, an HLA-A2 restricted nonameric peptide derived from NE and P3, has been demonstrated in acute myeloid leukemia (AML). We have successfully targeted PR1 in AML patients using PR1-peptide vaccine, anti-PR1/HLA-A2 antibody and PR1-specific cytotoxic T-lymphocytes (PR1-CTL). We have also identified the uptake and cross-presentation of NE and P3 by breast cancer, lung cancer and melanoma, which underlines their potential as immunotherapeutic targets in non-myeloid malignancies.Cathepsin G is also an azurophil granule serine protease that is highly expressed by AML blasts and leukemic stem cells. Our previous studies showed a high level of efficacy in targeting AML blasts that express CG1 (FLLPTGAEA) using CG1-specific CTL (CG1-CTL), while sparing normal hematopoietic cells. However, two previous reports (Fujiwara et al., Clinical Cancer Research, 2005 and Gorodkiewicz et al., Analytical Biochemistry, 2012) and our published data (Alatrash G, Leukemia, 2017) have reported CG expression in lymphoid leukemia. We therefore hypothesized that CG is an effective immunotherapeutic target in lymphoid malignancies, specifically acute lymphoid leukemia (ALL).We first analyzed CG expression in ALL patient samples. Using reverse phase protein array (RPPA), we analyzed CG expression in ALL blasts from 345 adult ALL patient samples. We detected CG in 345 patient samples at levels comparable to G-CSF stimulated myeloid progenitors. The differential expression of CG in sorted ALL blasts ranged from -1.8030 to 5.4390, with a median value of 0.3506. In estimating CG levels, we found that more than 15% of our ALL samples expressed Log2 concentrations of CG between 0.3 and 0.4 (Figure 1). This was comparable to what we have previously reported in AML. We then wanted to determine whether the ALL-associated CG was due to uptake or endogenous expression. We performed PCR and western blotting and confirmed CG expression in 4 of 9 and 9 of 9 patient ALL samples, respectively (Figure 2). To assess whether CG is also taken up by ALL, we examined CG uptake by the B-ALL cell lines SB, RS4, Nalm6 and HMY (B-ALL). ALL cell lines were incubated with CG protein at increasing doses and durations. Intracellular staining of CG followed by flow cytometry analysis was used to determine uptake of CG by ALL cell lines. Our data show that all of the ALL cell lines take up CG; uptake correlated directly with increasing doses and time of incubation up to 24 hours.Having characterized the expression of CG by ALL, we sought to determine its potential as an immunotherapeutic target, as we have previously shown for AML. In these experiments, CG1-specific CTLs were generated using standard dendritic cells methodology, interleukin-7 (IL-7), IL-2 and CG1-peptide pulsing. Expanded CG1-CTL were confirmed by staining cells with CG1 tetramer followed by flow cytometry analysis. We employed standard calcein-AM cytotoxicity assays to determine specific lysis. In these experiments, patient ALL sample UPN8 was pulsed with calcein-AM and then co-cultured with CG1-CTL for 4 hours. Our results indicated that UPN8 was effectively lysed by CG1-CTL, reaching a maximum specific lysis of ~30% at the highest effector:target ratio (Figure 3).Overall, our analysis confirms CG endogenous expression and uptake by ALL. Furthermore, we conclude that CG is an effective target for immunotherapy in B-ALL. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Role and Mechanism of PTPN21 Isoforms in Acute Lymphoblastic Leukemia Escaping NK Cell Killing

Relapse of acute lymphoid leukemia (ALL) is one of the most difficult issues in clinical treatment. There is strong correlation between gene profiles and recurrence in ALL. Previous studies have illustrated the importance of PTPN21 in the development of several kinds of tumors, such as bladder cancer, esophageal cancer, lymphoma etc. PTPN21 is highly expressed in the solid tumors above, which can reflect the extent and prognosis of malignancy. Whether PTPN21 plays a role in the development and progression of leukemia has not been reportedIn our previous study, we found that the mRNA expression level of PTPN21 in bone marrow monocytes of ALL patients was increased.Moreover, the ability of cell proliferation was increased after overexpressing PTPN21 in ALL cell lines via lentiviral transfection method.Besides, we designed two kinds of single guide RNA(sgRNA),which located in the exon 2 and exon7 of PTPN21,respectively. We found NALM6,which is one type of PH-ALL cell line ,had two kind of PTPN21 isoforms using PCR method,the longest CDS one(1174aa) and the shortest one(970aa).Using Crispr-Cas9 technology ,we had separately gained the NALM6 clones with PTPN21 knocking out in exon2 site and exon7 site,which stand for the longest isoform(1174aa) knocking out and all isoforms kncoking out ,respectively.We found the cytotoxicity of natural killer (NK) cells to NALM6 with knocking out PTPN21 gene in exon2 site obviously increased(figure 1a).While there was no similar result in the NALM6 clones with knocking out in exon7 of PTPN21(figure 1b). Our results suggested that PTPN21 was involved in the immune escaping process of ALL by NK cells, and the above two types of isoforms of PTPN21 play contary roles in immune killing process in ALL by NK cells. We then tested the expression profile of NK related ligands on the cell surface before and after gene knock-out throgh flow cytometry,such as ULBPs,CD155,CD112,HLA-ABC ect.The result showed after the longest isoform was knocked out from NALM6, The expression of HLA-E,CD112,HLA class I molecules on the cell surface was decreased.Especially, HLAI changed most obviously (figure 1c),and the chaperones of endogenous antigen presenting such as TAP1,TAP2,TAPBP,PSMB8,PSMB9 decreased significantly(figure 1d).we suspect it's the key reason of resulting in the decrease of HLA class I molecules on the cell surface, thus can block the KIR-HLAI signaling axis and improve the killing activity of NK cells.Together, our data suggest that different PTPN21 isoforms in ALL cells have different roles in mediating immune response by NK. There are mutual checks and balance between isoforms, which provide new idea and therapeutic target for the prevention and treatment of ALL recurrence.Figure 1:a-b. The cytotoxicity of natural killer (NK) cells to NALM6 with knocking out PTPN21 gene in exon2.The killing rate =CFSE+PI+/CFSE+. c-d. The cytotoxicity of natural killer (NK) cells to NALM6 with knocking out PTPN21 gene in exon7. The killing rate =CFSE+PI+/CFSE+. e. The expression of HLA class I molecules on the cell surface before and after PTPN21 knock-out in exon2 and exon7,respetively. f.The mRNA expression profiles of the chaperone of endogenous antigen presenting whether PTPN21 knock-out or not in exon2).(* p=0.05,**p=0.01,***p=0.001 [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Urtica dioica agglutinin (a plant lectin) has a caspase-dependent apoptosis induction effect on the acute lymphoblastic leukemia cell line

Urtica dioica agglutinin (UDA) is a very small plant lectin with anti-prostatic activity. In this study, we investigated the effect of UDA on proliferation and apoptosis induction in human acute lymphoid leukemia (ALL) cell lines. The effect of UDA on Jurkat and Raji cell proliferation was examined by MTS assay. Distribution of cell cycle phases was determined by PI staining and apoptosis was examined with annexin V/PI and western blot. Results showed UDA treatment reduced cell proliferation in cells by inducing apoptosis. PI staining was associated with a higher percentage of the cell population in sub G1. Caspase-8 and caspase-9 dependent apoptosis occurred in Jurkat cells. Generally, UDA treatment resulted in cell death in ALL cell lines and induced apoptosis in the T-ALL cell line, Jurkat, through extrinsic and intrinsic pathways. These results may be considered as a guide to working on UDA as an anti-leukemic drug in the future.

Abstract 1128: Identification of arginine methyltransferase PRMT5 as a novel therapeutic target in T-cell acute lymphoblastic leukemia

Abstract Advances in risk-adapted cytotoxic chemotherapy, hematopoietic stem cell transplantation and supportive care have contributed to significant improvements in the survival of patients with acute lymphoid leukemia (ALL) and acute myeloid leukemia (AML) over the past few decades. However, despite such progress, a significant percentage of both adult and pediatric leukemia patients become refractory to therapy or relapse and eventually die of disease. Hence, there remains an urgent need for the development of effective and targeted therapies for acute leukemia. Recent genetic profiling of solid and hematologic malignancies has identified epigenetic factors as a critical group of genes recurrently mutated in cancer. Additionally, epigenetic dysregulation has been shown to play an important role in the development, progression and maintenance of leukemia. Therefore, pharmacological inhibition of epigenetic factors represents a potential avenue for the development of novel epigenetic-targeted therapies. In order to identify epigenetic vulnerabilities in leukemia, we developed an epigenetic-focused shRNA screen to search for novel therapeutic targets in human leukemia cell lines both in vitro and in vivo. Specifically, T- and B-ALL cell lines were transduced with a library of shRNAs targeting 449 genes including epigenetic readers, writers and erasers and other chromatin-related factors. Selected cells were subsequently cultured in vitro and concurrently injected into mice. Engraftment of inoculated cells and disease progression were monitored through bioluminescence imaging. Amongst the universe of epigenetic regulatory proteins, the arginine methyl transferase, PRMT5, emerged as the most significantly depleted factor in both in vitro and in vivo screenings. Chemical inhibition of PRMT5 enzymatic activity effectively reduced protein symmetric dimethyl arginine methylation, altered splicing, inhibited cell growth and promoted apoptosis of both ALL and AML cell lines in vitro. In addition, inhibition of PRMT5 in vivo using patient-derived xenograft (PDX) T-ALL mouse models demonstrated diminished tumor growth and prolonged survival. Notably, quantification of peripheral blood cell numbers showed that pharmacologic PRMT5 inhibition was well tolerated and did not affect normal hematopoiesis in mice suggesting that a therapeutic window exists for anticancer drugs targeting PRMT5 in acute leukemia. Overall, our data indicates that pre-mRNA processing and in particular RNA splicing modulation may represent novel therapeutic targets in leukemia. Note: This abstract was not presented at the meeting. Citation Format: Yunyue Wang, Hui Huang, Daniel Diolaiti, Marta Sanchez Martin, Beata Modzelewski, Lianna J. Marks, Allison R. Rainey, Ervin S. Gaviria, Maria L. Sulis, Filemon S. Dela Cruz, Adolfo A. Ferrando, Andrew L. Kung. Identification of arginine methyltransferase PRMT5 as a novel therapeutic target in T-cell acute lymphoblastic leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1128. doi:10.1158/1538-7445.AM2017-1128

KML001 and doxercalciferol induce synergistic antileukemic effect in acute lymphoid leukemia cells.

KML001 (NaAsO2, sodium metaarsenite, KOMINOX), a kind of arsenic compound, that has shown promising efficacy in non-Hodgkin's lymphoma(NHL) both invitro and invivo. In our study, the antileukemic effect of KML001 on acute lymphoid leukemia(ALL) and its mechanism of action were investigated. The results showed that KML001 inhibited cell proliferation in two types of ALL cell lines, CCRF-CEM and Molt-4. Exposure of ALL cells to KML001 induced apoptosis in a time-dependent manner. KML001 caused cell cycle arrest at G2/M phase instead of G0/G1 phase shown in other leukemia cells. In addition, we also tested the possibility of synergy of KML001 with doxercalciferol, a vitaminD2 derivative. Also, we found that a combination of KML001 with doxercalciferol showed a synergistic effect on ALL cell lines and this could be due to its different mechanism of action. Overall, our findings demonstrated KML001 could be a promising antileukemic agent especially when it is combined with doxercalciferol in ALL treatment.

CD47 Blockade Enhances Therapeutic Activity of TCR Mimic Antibodies to Ultra-Low Density Cancer Epitopes through Cytokine Feed Forward Mechanisms

INTRODUCTIONT Cell Receptor mimic (TCRm) antibodies to low-density peptide epitopes from undruggable intracellular proteins presented in the context of major histocompatibility (MHC) molecules are therapeutically effective in mouse models of human cancers. CD47 blockade by use of a high affinity SIRPα variant protein (CV1) has been shown to improve the effects of monoclonal antibodies to high-density antigens in tumor models by enhancement of antibody dependent cellular phagocytosis (ADCP). We asked if combination therapy with a TCRm antibody to Preferentially Expressed Antigen in Melanoma (PRAME) could enhance activity of both drugs in vitro and in vivo. Additionally, we explored the role of macrophage-secreted cytokines in the enhanced in vivo activity.METHODSWe performed in vitro ADCP assays with human acute myeloid and acute lymphoid leukemia cell lines containing antigens of interest using the two agents alone and in combination. We performed therapy experiments in NSG mice using the same leukemia cell lines transformed with a luciferase vector and measured tumor burden through bioluminescent imaging. Survival was measured. We examined cell-surface expression of epitopes of interest and HLA on cell lines in vitro after incubation with IFNγ and TNFα using flow cytometry and performed in vitro ADCP assays with the leukemia cell lines after pretreatment with IFNγ.RESULTSCV1 and TCRm antibody showed additive effects in vitro with a statistically significant increase in phagocytosis in both antigen positive cell lines with combination therapy versus single agent therapy. CV1 and TCRm antibody showed greater than additive therapeutic effects in vivo with a 3-log reduction in leukemia burden relative to control untreated mice and a 5-10 fold reduction relative to single agent groups. After therapy was stopped, mice treated with the combination had statistically significant increases in survival (p<0.0001). IFNγ and TNFα led to up-regulation of cell surface HLA-A*02:01. Additionally, the cytokines led to up-regulation of the PRAME derived epitope of interest. Pretreatment of human leukemia cell lines with IFNγ led to statistically significant increases in ADCP in vitro.CONCLUSIONSThe elimination of anti-phagocytic signal produced by CD47 blockade with the high affinity SIRPα variant CV1, combined with the pro-phagocytic signal of Fc receptor engaging TCRm was effective even with an ultra-low density epitope (700-3000 sites per cell) in vitro and in vivo. A greater than additive effect was seen in two tumor models. These results support the potency of this drug combination. The large enhancement in activity in vivo vs. in vitro may be explained by macrophage-released cytokines leading to increased presentation of epitopes of interest and increased tumor kill. DisclosuresLiu:Eureka Therapeutics: Employment, Equity Ownership, Patents & Royalties. Garcia:Alexo Therapeutics: Equity Ownership.

ShRNA screening identifies JMJD1C as being required for leukemia maintenance

AbstractEpigenetic regulatory mechanisms are implicated in the pathogenesis of acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL). Recent progress suggests that proteins involved in epigenetic control are amenable to drug intervention, but little is known about the cancer-specific dependency on epigenetic regulators for cell survival and proliferation. We used a mouse model of human AML induced by the MLL-AF9 fusion oncogene and an epigenetic short hairpin RNA (shRNA) library to screen for novel potential drug targets. As a counter-screen for general toxicity of shRNAs, we used normal mouse bone marrow cells. One of the best candidate drug targets identified in these screens was Jmjd1c. Depletion of Jmjd1c impairs growth and colony formation of mouse MLL-AF9 cells in vitro as well as establishment of leukemia after transplantation. Depletion of JMJD1C impairs expansion and colony formation of human leukemic cell lines, with the strongest effect observed in the MLL-rearranged ALL cell line SEM. In both mouse and human leukemic cells, the growth defect upon JMJD1C depletion appears to be primarily due to increased apoptosis, which implicates JMJD1C as a potential therapeutic target in leukemia.

Human Surfactant Protein D Alters Oxidative Stress and HMGA1 Expression to Induce p53 Apoptotic Pathway in Eosinophil Leukemic Cell Line

Surfactant protein D (SP-D), an innate immune molecule, has an indispensable role in host defense and regulation of inflammation. Immune related functions regulated by SP-D include agglutination of pathogens, phagocytosis, oxidative burst, antigen presentation, T lymphocyte proliferation, cytokine secretion, induction of apoptosis and clearance of apoptotic cells. The present study unravels a novel ability of SP-D to reduce the viability of leukemic cells (eosinophilic leukemic cell line, AML14.3D10; acute myeloid leukemia cell line, THP-1; acute lymphoid leukemia cell lines, Jurkat, Raji; and human breast epithelial cell line, MCF-7), and explains the underlying mechanisms. SP-D and a recombinant fragment of human SP-D (rhSP-D) induced G2/M phase cell cycle arrest, and dose and time-dependent apoptosis in the AML14.3D10 eosinophilic leukemia cell line. Levels of various apoptotic markers viz. activated p53, cleaved caspase-9 and PARP, along with G2/M checkpoints (p21 and Tyr15 phosphorylation of cdc2) showed significant increase in these cells. We further attempted to elucidate the underlying mechanisms of rhSP-D induced apoptosis using proteomic analysis. This approach identified large scale molecular changes initiated by SP-D in a human cell for the first time. Among others, the proteomics analysis highlighted a decreased expression of survival related proteins such as HMGA1, overexpression of proteins to protect the cells from oxidative burst, while a drastic decrease in mitochondrial antioxidant defense system. rhSP-D mediated enhanced oxidative burst in AML14.3D10 cells was confirmed, while antioxidant, N-acetyl-L-cysteine, abrogated the rhSP-D induced apoptosis. The rhSP-D mediated reduced viability was specific to the cancer cell lines and viability of human PBMCs from healthy controls was not affected. The study suggests involvement of SP-D in host’s immunosurveillance and therapeutic potential of rhSP-D in the eosinophilic leukemia and cancers of other origins.

L-Asparaginase Sensitivity and Asparagine Synthetase Expression In Primary Tumor Cells From AML Patients

Abstract Introduction The rational of use of L-asparaginase (L-Aspa) is based on asparagine synthetase (ASNS) deficiency in leukemic cells. Its efficacy is due to its capacity to deplete plasmatic asparagine, starving the leukemic cells and subsequently inhibiting protein synthesis. It is a mainstay in the treatment of acute lymphoid leukemia (ALL), where it is established that resistance to treatment is in part related to detectable expression of ASNS (Aslanian et al., 2001; Su et al., 2008). In acute myeloid leukemia (AML), promising results have been obtained in clinical trials (Capizzi et al., 1988), with an improvement of complete remission rates from 18% to 54% in refractory patients &lt;60 year old and from 0% to 31% in refractory patients &gt;60 year old. More recently, it has been reported that leukemic cells from AML patients with M1, M4 and M5 FAB subtypes were more sensitive to L-Aspa (Okada et al., 2003).The aim of this study was to investigate the sensitivity to L-Aspa and the ASNS expression in an AML cell line (HL-60) and in primary leukemic cells from newly diagnosed AML patients. Materials and methods AML (HL-60) and ALL (MOLT-4) cell lines were grown according to ATCC recommendations. Primary leukemic cells from the bone marrow of 24 AML patients (median age: 69 years; range: 2-83) were harvested on EDTA and isolated by Ficoll density gradient within 72h. ASNS expression was determined by western-blot on isolated leukemic cells and expressed as a ratio ASNS/cyclophilin A. When a sufficient amount of leukemic cells was available, sensitivity to L-Aspa (expressed as an IC50 - concentration inhibiting 50% of cell viability) was evaluated in vitro by incubating various concentrations of L-Aspa (0.001 to 10 IU/mL) with the cells and by measuring the cell viability with a counting kit (CCK-8 viability assay) at day 4. Results Determination of IC50 for the HL-60 cell line demonstrated that these cells were equally sensitive to L-Aspa than the ALL cell line MOLT-4 in vitro (0.23 IU/mL versus 0.19 IU/mL, respectively). The expression of ASNS in the HL-60 cell line was low but higher than in MOLT-4 which is a well known ASNS deficient cell line. IC50 determination was possible on 17/24 patients. Seven displayed a high sensitivity to L-Aspa (IC50 &lt; 0.01 IU/mL) whereas 5 displayed a moderate sensitivity (IC50 &lt; 0.5 IU/mL). Remaining 5 patients were resistant to L-Aspa. The cells from the healthy subject were resistant (IC50 &gt; 10 IU/mL). To date, ASNS expression has been evaluated on 16 patients with ratio ranges from 0 to 2.27: six were negative, 4 low positive (&lt; 0.2), and 6 positive (&gt; 0.5, amongst them 4 were &gt; 1). No correlation was observed between ASNS expression and FAB grade. However, patients with blasts sensitive to L-Aspa had mainly M1 or M5 AML. Conclusion AML cell line HL-60 and 71% of primary cells from AML patients were found sensitive to L-Aspa. The sensitivity of cells from M1 and M5 AML patients is consistent with the findings of Okada et al. (2003). Globally, these results suggest that L-Aspa is effective for killing AML cells. Based on the epidemiology of AML subtypes (Selter et al., 2011) and our results, L-Aspa therapy may be beneficial for 50-70% of patients with AML. However, L-Aspa has only been used scarcely in the treatment of AML, mainly because of the commonly observed adverse effects that impair its use. A new formulation of L-Aspa encapsulated in homologous red blood cells was reported with a better safety profile, allowing its use even in elderly patients (Hunault et al., ASH 2012). A clinical study is currently recruiting patients unfit for intensive chemotherapy in order to evaluate its efficacy in combination with low-dose cytarabine (NCT01810705) in AML. In this study, L-Aspa sensitivity and ASNS expression in primary tumor cells at diagnosis will be explored to investigate the relationship with clinical response. Disclosures: Berlier: ERYTECH Pharma: Employment. Aguera:ERYTECH Pharma: Employment. Gallix:ERYTECH Pharma: Employment. Bertrand:ERYTECH Pharma: Principal Investigator Other. Thomas:ERYTECH Pharma: Principal Investigator Other; Orphan Europe: Consultancy. Godfrin:ERYTECH Pharma: Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees.

Blast Asparagine Synthetase Deficiency in Acute Myeloid Leukemia

AbstractAbstract 4333 IntroductionL-asparaginase (L-Aspa) is one of the standard components of acute lymphoid leukemia (ALL) therapy. Its efficacy as an antineoplasic agent is due to its capacity to deplete plasmatic asparagine, starving the leukemic cells and subsequently inhibiting protein synthesis.In vitro studies have already shown the sensitivity to L-Aspa of leukemic cells from patients with acute myeloid leukemia (AML), depending on the French-American-British (FAB) subtype (Zwaan et al., 2000; Okada et al., 2003). Despite promising results in clinical trials (Capizzi et al., 1988; Wells et al., 1993), L-Aspa has only been used scarcely in the treatment of AML, mainly because of the adverse effects observed commonly that impair its use.The existence of a new formulation of L-Aspa (L-Aspa encapsulated in heterologous red blood cells) with a better safety profile allows considering its use for the treatment of AML (Godfrin et al., 2012).The sensitivity to L-Aspa may be inversely correlated to their expression of asparagine synthetase (ASNS, an enzyme catalyzing the intracellular synthesis of asparagine). The aim of this study was to investigate the potential of L-Aspa for AML treatment by determining the leukemic cell expression of ASNS and their sensitivity to L-Aspa. Materials and methodsStudies were performed on an AML cell line (HL-60) and on leukemic cells isolated from the bone marrow of AML patients by Ficoll density gradient.The IC50 (concentration inhibiting 50% of cell viability) was determined in vitro by incubating various concentrations of L-Aspa with the cells and measuring the cell viability with a cell counting kit (CCK-8 viability assay).ASNS expression was determined by western-blot. ResultsAs a preliminary, determination of IC50 for the HL-60 cell line demonstrated that these cells were equally sensitive to L-Aspa than the ALL cell line MOLT-4 in vitro(0.23 IU/mL versus 0.19 IU/mL, respectively). The expression of ASNS in the HL-60 cell line was low in comparison with other cancer cell lines.Concerning blasts isolated from AML patients, 2/3 patients displayed an IC50 < 0.01 IU/mL whereas 1/3 displayed an IC50 as low as 0.13 IU/mL, which means a high sensitivity to L-Aspa. All these patients were negative for ASNS expression.On 6 patients tested for ASNS expression, 5 had their blasts negative whereas one was positive. Patients with blasts negative for ASNS expression were all affected by FAB M5 or M1 AML whereas patient with blasts positive was diagnosed with a M2 AML. ConclusionBoth AML cell line and cells isolated from AML patients were sensitive to L-Aspa. In all clinical cases, high sensitivity and/or lack of ASNS expression were linked to a FAB M5 or M1 AML, consistent with data from literature suggesting a higher sensitivity of M1, M4 and M5 AML subtypes.The only clinical case positive for ASNS expression was a FAB M2 AML, consistent with literature that indicates an in vitro resistance of the M2 AML subtype to L-Aspa.Globally, these results suggest that L-Aspa is effective for killing AML cells with low/no ASNS expression. Thus, thanks to its low toxicity profile, L-Aspa may be considered as a potential therapy for FAB subtypes or individuals characterized by low/no ASNS expression. Based on the epidemiology of AML subtypes (Selter et al., 2011), L-Aspa therapy may be beneficial for 50% of patients with AML.These results finally highlight the necessity of the determination of the grade and/or the expression of ASNS in leukemic cells to select AML patients at potential for L-Aspa therapies. Disclosures:Berlier:ERYTECH Pharma: Employment. Aguera:ERYTECH Pharma: Employment. Campion:ERYTECH Pharma: Employment. Gay:ERYTECH Pharma: Employment. Godfrin:ERYTECH Pharma: COO Other.

EphrinB1 Activation As a Potential New Treatment Option in AML

Abstract 5235Aberrant Ephrin signaling has been shown to be an important pathway that contributes to the pathogenesis of many solid tumors (Surawska et al. Cytokine & Growth factor reviews 2004). Deregulated ephrin receptor (Eph) and ligand (Efn) expression is often associated with poor prognosis in solid tumors. Ephrin receptor and ligand overexpression can result in tumorigenesis through induced tumor growth, tumor cell survival, angiogenesis and metastasis (Surawska et al. Cytokine & Growth Factor Reviews 2004; Campbell et al. Curr. Isues Mol. Biol. 2008; Chen et al. Cancer Research 2008). In normal cells Eph receptors and ligands play key roles in vascular patterning, where they function in endothelial cell migration, and proliferation (Adams et al, Genes Dev. 1999; Zhang et al., Blood 2001). Thus far particularly EphB4 receptor and ephrin-B2 ligand have been implicated in the process of normal angiogenesis. In acute myeloid leukemia (AML) patients it was found that bone marrow biopsies at diagnosis exhibited enhanced microvessel density (MVD) (de Bont ES et al., BJH 2001; Byrd JC et al., Blood 2002; Padro et al., Blood 2000). Normal hematopoietic stem cells (HSCs) express the following mRNA transcripts ephrin receptors EphA1, EphA2, EphB2, and EphB4 and ephrin ligands EfnA3, EfnA4, and EfnB2. Moreover, overexpression of EphB4 receptor in HSCs (from cord blood) resulted in enhanced differentiation towards megakaryocytes (Wang et al. Blood 2002). In AML cell lines there is a common co-expression on protein level observed between EphB4 receptor and ephrin-B2 ligand. Recently, an aberrant DNA methylation of ephrin receptors and ligands was described in acute lymphocytic and myelocytic leukemia cell lines (Kuang et al. Blood 2010). In addition, restoration of EphB4 expression in an acute lymphoid leukemia cell line resulted in reduced proliferation and apoptotic cell death. These data suggests that the ephrin signaling pathway might play an important role in leukemia. In a previous study we have found high kinase activity of EphB receptors and high phosphorylation levels of EphB receptors in AML samples, as measured using kinase arrays and proteome profiler arrays. In this study, we have found extensive membrane expression of EphB1 on AML cell lines and primary AML blasts. To identify the role of Ephrin signaling in AML, two AML cell lines THP-1 and HL60 with an EphB1 membrane expressing cell percentage of 70% and 20% respectively were chosen for stimulation with Ephrin-B1 ligand. Treatment of these cell lines with Ephrin-B1 ligand resulted in a decreased proliferation 30% in THP-1 cells versus 22% in HL60 cells and increased apoptosis 23% in THP-1 cells and 4% in HL60 cells. Of note, the most prominent effect of Ephrin-B1 stimulation was found in THP-1 cells, this cell line contained a higher percentage of EphB1 membrane expressing cells. We further investigated the mechanism through which EphB1 reduces leukemic cell growth and induces leukemic cell death in THP-1 cells. Westernblot analysis of cell cycle regulators showed that expression of the anti-apoptotic protein BCL2 is reduced upon Ephrin-B1 ligand stimulation and the expression of the pro-apoptotic protein BAX is induced. In addition, mRNA expression of the cell cycle inhibitor of cell cycle progression p21 was found to be 2,5 fold upregulated in ephrin-B1 ligand treated cells compared to untreated control cells. MGG stainings of Ephrin-B1 treated cells revealed multiple cells with two nuclei in both THP-1 and HL60 cells. These results indicate that a high percentage of AML cells express EphB1 receptor on the membrane and that stimulation of these cells with Ephrin-B1 ligand results in reduced leukemic growth and increased cell death. EphrinB1 activation in AML deserves further investigation considering EphB1 as a putative new treatment option for AML patients. Disclosures:No relevant conflicts of interest to declare.

Apoptosis induced by ZnPcH1-based photodynamic therapy in Jurkat cells and HEL cells

Photodynamic therapy (PDT) can selectively and effectively kill tumor cells, and photosensitization is the key to these anti-tumor effects. In this study, we investigated the killing mechanisms of the photosensitizer ZnPcH1 (a mono-α-substituted zinc(II) phthalocyanine synthesized in China), in the acute lymphoid leukemia cell line Jurkat and the acute erythroleukemia cell line HEL. Results from acridine orange/ethidium bromide fluorescence staining, DNA gel electrophoresis, and Annexin-V(FITC/PI) double-stained flow cytometry analysis indicated that ZnPcH1-PDT induced apoptosis in Jurkat and HEL cells, with Jurkat cells being more sensitive. Following ZnPcH1-PDT treatment, upregulation of p53 and Bax, downregulation of HSP70, Bcl-2 and Akt, and inhibition of the phosphorylation of Akt and GSK3β were observed. Our results establish a theoretical basis for the application of ZnPcH1-PDT in the treatment of acute leukemia.

CD45 regulates homing and engraftment of immature normal and leukemic human cells in transplanted immunodeficient mice

Bone marrow homing and engraftment by clinically transplanted hematopoietic stem and progenitor cells is a complex process that is not fully understood. We report that the pan-leukocyte CD45 phosphatase plays an essential role in trafficking and repopulation of the bone marrow by immature human CD34(+) cells and leukemic cells in transplanted nonobese diabetic severe combined immunodeficient mice. Inhibiting CD45 function by blocking antibodies or a CD45 inhibitor impaired the motility of both normal and leukemic human cells. Blocking CD45 inhibited homing and repopulation by immature human CD34(+) cells as well as homing of primary patient leukemic cells. In addition, CD45 inhibition negatively affected development of hematopoietic progenitors invitro and their recovery in transplanted recipients invivo, revealing the central role of CD45 in the regulation of hematopoiesis. Moreover, CD45 blockage induced a hyperadhesive phenotype in immature human progenitor cells as well as in murine leukocytes, leading to their defective adhesion interactions with endothelial cells. This phenotype was further manifested by the ability of CD45 blockage to prevent breakdown of adhesion interactions in the BM, which inhibited murine progenitor mobilization. The substantial effects of a direct CD45 inhibition point at its essential roles in cell trafficking, including murine progenitor cell mobilization and both normal immature and leukemic human hematopoietic cells as well as regulation of hematopoiesis and engraftment potential.

Reactivating aberrantly hypermethylated p15 gene in leukemic T cells by a phenylhexyl isothiocyanate mediated inter-active mechanism on DNA and chromatin

BackgroundWe have previously demonstrated that phenylhexyl isothiocyanate (PHI), a synthetic isothiocyanate, inhibits histone deacetylases and remodels chromatins to induce growth arrest in HL-60 myeloid leukemia cells in a concentration-dependent manner.MethodsTo investigate the effect of PHI, a novel histone deacetylases inhibitor (HDACi), on demethylation and activation of transcription of p15 in acute lymphoid leukemia cell line Molt-4, and to further decipher the potential mechanism of demethylation, DNA sequencing and modified methylation specific PCR (MSP) were used to screen p15-M and p15-U mRNA after Molt-4 cells were treated with PHI, 5-Aza and TSA. DNA methyltransferase 1 (DNMT1), 3A (DNMT3A), 3B (DNMT3B) and p15 mRNA were measured by RT-PCR. P15 protein, acetylated histone H3 and histone H4 were detected by Western Blot.ResultsThe gene p15 in Molt-4 cells was hypermethylated and inactive. Hypermethylation of gene p15 was attenuated and p15 gene was activated de novo after 5 days exposure to PHI in a concentration-dependent manner. DNMT1 and DNMT3B were inhibited by PHI (P < 0.05). Alteration of DNMT3A was not significant at those concentrations. Acetylated histone H3 and histone H4 were accumulated markedly after exposure to PHI.ConclusionPHI could induce both DNA demethylation and acetylated H3 and H4 accumulation in Molt-4 cells. Hypermethylation of gene p15 was reversed and p15 transcription could be reactivated de novo by PHI.

The Mir-23a∼Mir-27a∼Mir-24 Cluster Acts as a Tumor Suppressor In Leukemias by Post-Transcriptional Regulation of 14-3-3 Proteins

AbstractAbstract 3145We and others have found that microRNAs (miRs) play major roles in normal hematopoietic differentiation, evidenced by the discovery of a small set of hematopoietic stem-progenitor cell (HSPC)-expressed miRs (HE-miRs) highly expressed in normal human CD34+ cells, which post-transcriptionally regulate specific mRNAs involved in hematopoiesis. Microarray data indicated that 1 of these HE-miRs, miR-27a (transcribed as part of the miR-23a cluster consisting of 3 coordinately transcribed miRs: miR-23a, miR-27a, miR-24-2) is absent or expressed at much lower levels in several human acute leukemias, as compared to normal human HSPCs. We further investigated the expression of miR-27a in acute leukemias, and confirmed via qRT-PCR that there is ≥ 2-fold decreased miR-27a expression in 3 of 6 acute myeloid leukemia (AML), 4 of 5 B precursor acute lymphoid leukemia (ALL), and 3 of 3 T cell ALL cell lines tested (10 of 14 cell lines total). Additionally, 5 of 7 primary B precursor ALL and 5 of 5 primary T cell ALL samples had decreased miR-27a expression compared to normal HSPCs. Over-expression of miR-27a in K562 cells resulted in 4-fold decreased proliferation and 2-fold increased apoptosis compared to control cells. Similarly, over-expression of miR-27a in 3 other acute leukemia cell lines (TF1, HL60, and REH) yielded a significant increase in the percentage of AnnexinV+/7AAD- cells compared to control cells (TF1 = 21.3% vs. 12.0%; HL60 = 19% vs. 4.5%; REH = 21.5% vs. 4.7%). Members of the 14-3-3 protein family act as oncogenes and support cell survival by interacting with and negatively regulating pro-apoptotic proteins such as Bax and Bad. The 14-3-3β isoform (YWHAB) is a predicted miR-27a target gene, based on transcriptome analysis of normal HSPCs, and miR prediction algorithms revealed 2 predicted miR-27a binding sites in its 3'UTR. In addition, there are 5 predicted miR-24 binding sites in the 3'UTR and coding region of YWHAB, and 4 other 14-3-3 isoforms have multiple predicted miR-23a cluster member binding sites in their mRNA transcripts: 14-3-3θ (YWHAQ, 1 miR-27a site), 14-3-3γ (YWHAG, 2 miR-23a, 5 miR-27a and 3 miR-24 sites), 14-3-3ζ (YWHAZ, 3 miR-27a and 5 miR-24 sites), and 14-3-3ε (YWHAE, 1 miR-27a and 1 miR-24 site). The expression levels of the other 2 cluster members, miR-23a and miR-24, are also decreased in human acute leukemia cell lines and patent samples, similar to miR-27a expression in the same leukemia cases. We have confirmed via luciferase reporter binding assays and Western blot analyses that both miR-27a and miR-24 specifically regulate 14-3-3β protein expression levels, while miR-27a specifically regulates 14-3-3θ. Moreover, combined miR-27a and miR-24 over-expression decreased 14-3-3ε protein expression on Western blots. Since knockdown of 14-3-3 family proteins is established to result in apoptosis in hematopoietic cells including K562, post-transcriptional downregulation of 14-3-3 proteins by miR-27a, miR-23a and miR-24 contributes to the miR-27a-induced apoptosis in leukemias. Thus, miR-27a acts as a traditional tumor suppressor gene and members of the miR-23a cluster cooperate to regulate oncogenic 14-3-3 isoforms, and consequently, cell survival, in human acute leukemias. Disclosures:No relevant conflicts of interest to declare.

Oncogenic CBL Mutants Have Transforming Potential in Cells Expressing the FLT3 Tyrosine Kinase.

CBL is a E3-ubiquitin ligase, that negatively regulates many receptor tyrosine kinases (RTKs). Translocations (t(4;11); t(11;14) involving CBL in humans and two oncogenic CBL deletion mutants, CBL-70Z and v-CBL, inducing B-cell lymphomas in mice, were described. The RTK Fms-like tyrosine kinase 3 (FLT3) is expressed by the leukemic cells of 70–90% of patients with acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL) and is highly implicated in the malignant transformation by harbouring activating mutations, aberrant autocrine stimulation or overexpression.We hypothesized that CBL could play a role in regulating FLT3 activity and if mutated, could cause aberrant FLT3 signaling in hematopoietic cells. To analyze if CBL mutants could lead to transformation of FLT3-expressing cells we stably transduced Ba/F3 cells with CBL-WT, CBL-70Z or v-CBL alone or together with FLT3-WT. Coexpression of FLT3-WT and a CBL mutant, CBL-70Z or v-CBL, but not CBL-WT or expression of a CBL-construct alone, conferred IL-3 independent growth to Ba/F3 cells. In presence of FLT3 ligand FLT3-WT/CBLmutant-expressing cells showed hyperproliferation. To determine whether the proliferative advantage of FLT3-WT/CBL-70Z and FLT3-WT/v-CBL cells is mediated by FLT3 we cultivated the cells in presence of selective FLT3 inhibitors, SU5614 and PKC412. Both inhibitors were able to abrogate the IL-3 independent and FL-stimulated growth of FLT3-WT/CBL-70Z and FLT3-WT/v-CBL cells. The FLT3-WT receptors and the downstream signaling pathway, STAT5, were constitutively active in FLT3-WT/CBLmutant-expressing cells in contrast to control cells. To clarify the mechanism of transformation we performed internalization assays. The rate and speed of internalization of the FLT3-WT receptors were not altered in FLT3-WT/CBL-70Z and FLT3-WT/v-CBL cells compared to FLT3-WT cells. However, we could show that CBL-WT promotes FLT3 degradation. To investigate if CBL mutations play a role in acute leukemias we screened the cDNA of 62 AML and 6 ALL cell lines and found a CBL deletion mutant in MOLM-13 and MOLM-14 cells lacking exon 8, which comprises parts of the linker and RING finger domain. Hence, this mutation targets the same functionally important regions of the CBL protein than the CBL-70Z deletion.In summary, CBL-70Z and v-CBL, but not CBL-WT, confer a transforming potential to cells expressing FLT3. The pro-proliferative phenotype of FLT3-WT/CBL-70Z and FLT3-WT/v-CBL cells is mediated by an increase in FLT3 tyrosine kinase activity. The CBL-70Z and v-CBL mutations were hypothesized to act in a dominant negative manner abrogating the negativ-regulatory function of CBL-WT. We identified a CBL deletion mutant in the MOLM-13 and MOLM-14 cells, that is reminiscent of CBL-70Z, indicating that CBL mutations might play a role in the pathogenesis of acute leukemias.

Detection and Functional Analysis of CD8+ T Cells Specific for PRAME: a Target for T-Cell Therapy

Preferentially expressed antigen on melanomas (PRAME) is an interesting antigen for T-cell therapy because it is frequently expressed in melanomas (95%) and other tumor types. Moreover, due to its role in oncogenic transformation, PRAME-negative tumor cells are not expected to easily arise and escape from T-cell immunity. The purpose of this study is to investigate the usefulness of PRAME as target for anticancer T-cell therapies. HLA-A*0201-subtyped healthy individuals and advanced melanoma patients were screened for CD8+ T cells directed against previously identified HLA-A*0201-binding PRAME peptides by IFN-gamma enzyme-linked immunosorbent spot assays and tetramer staining. PRAME-specific T-cell clones were isolated and tested for recognition of melanoma and acute lymphoid leukemia (ALL) cell lines. PRAME mRNA expression was determined by quantitative real-time reverse transcription-PCR. In 30% to 40% of healthy individuals and patients, PRA(100-108)-specific CD8+ T cells were detected both after in vitro stimulation and directly ex vivo after isolation by magnetic microbeads. Although CD45RA- memory PRA(100-108)-specific T cells were found in some individuals, the majority of PRA(100-108)-tetramer+ T cells expressed CD45RA, suggesting a naive phenotype. PRA(100-108)-tetramer+ T-cell clones were shown to recognize and lyse HLA-A*0201+ and PRAME+ melanoma but not ALL cell lines. Quantitative real-time reverse transcription-PCR showed significantly lower PRAME mRNA levels in ALL than in melanoma cell lines, suggesting that PRAME expression in ALL is below the recognition threshold of our PRA(100-108)-tetramer+ T cells. These data support the usefulness of PRAME and in particular the PRA(100-108) epitope as target for T-cell therapy of PRAME-overexpressing cancers.

Effects of herbimycin A and its derivatives on growth and differentiation of Ph 1-positive acute lymphoid leukemia cell lines

The molecular basis of the Philadelphia chromosome (Ph 1) is a structurally altered c-abl ( bcr/abl) gene which encodes an abnormally large protein with protein tyrosine kinase activity. Herbimycin A, an inhibitor of tyrosine kinase, preferentially inhibited the growth of Ph 1-positive acute lymphoid leukemia (ALL) cell lines, as well as Ph 1-positive chronic myeloid leukemia (CML) cell lines. Although noncytotoxic concentrations of herbimycin A induced erythroid differentiation of two CML-derived cell lines, K562 and KU812, in a previous study, the differentiation-inducing effect of herbimycin A on Ph 1-positive ALL cell lines was less strong. Herbimycin A enhanced some differentiation-associated properties of one Ph 1-positive ALL cell line, L2, but the effect of herbimycin A on the other Ph 1-positive ALL cell lines was cytotoxic rather than cytostatic (differentiation-inducing). Several derivatives of herbimycin A were synthesized and their effects on the cell proliferation of Ph 1-positive CML and ALL cell lines were examined. The sensitivities of the Ph 1-positive cell lines to herbimycin A derivatives were different from the data on the rat kidney cell line infected with Rous sarcoma virus (v- src) derived from a previous study, suggesting bcr/abl kinase may differ in sensitivity from other tyrosine kinases. Moreover, the sensitivities of the ALL cell lines were not the same as those of the CML cell lines. These results suggest that a specific inhibitor of bcr/abl kinase could be an effective antileukemic agent against Ph 1-positive CML or ALL.

Deletion of the Human Retinoblastoma Gene in Primary Leukemias

As an initial step in evaluating the role of tumor suppressor genes in leukemogenesis, we surveyed primary leukemia cells from 130 patients for possible deletion of the retinoblastoma susceptibility (Rb) gene by Southern blot analysis. Two of them clearly showed homozygous deletion of Rb alleles. The first patient was a pre-B acute lymphoid leukemia (ALL) associated with a cytogenetic translocation: t(14;16)(q24;q22). The deletion was located at the 3' portion of the Rb gene, very close to the site of Rb gene deletion recently identified in an ALL cell line. The absence of Rb110 protein was further confirmed by Western blot analysis. The second patient was a chronic myelomonocytic leukemia (CMMoL), terminated in acute blastic transformation. Deletion of the 5' portion of Rb gene was found in leukemic cells in the chronic stage. The results indicated that inactivation of the Rb gene occurred in certain cases of leukemia. Its significance warrants further study.

Deletion of the human retinoblastoma gene in primary leukemias

As an initial step in evaluating the role of tumor suppressor genes in leukemogenesis, we surveyed primary leukemia cells from 130 patients for possible deletion of the retinoblastoma susceptibility (Rb) gene by Southern blot analysis. Two of them clearly showed homozygous deletion of Rb alleles. The first patient was a pre-B acute lymphoid leukemia (ALL) associated with a cytogenetic translocation: t(14;16)(q24;q22). The deletion was located at the 3′ portion of the Rb gene, very close to the site of Rb gene deletion recently identified in an ALL cell line. The absence of Rb110 protein was further confirmed by Western blot analysis. The second patient was a chronic myelomonocytic leukemia (CMMoL), terminated in acute blastic transformation. Deletion of the 5′ portion of Rb gene was found in leukemic cells in the chronic stage. The results indicated that inactivation of the Rb gene occurred in certain cases of leukemia. Its significance warrants further study.