ARC Is Regulated by MAPK and PI3K and Confers Drug Resistance and Survival Advantage to AML in Vitro and in Vivo

Abstract Abstract 893 ARC (Apoptosis repressor with caspase recruitment domain) is a unique antiapoptotic protein that has been shown to suppress the activation of both intrinsic and extrinsic apoptosis. We previously reported that ARC is one of the most potent adverse prognostic factors in AML and that high ARC protein expression predicted shorter survival and poor clinical outcome in patients with AML (Carter BZ et al., Blood 2011). Here we report how ARC is regulated and its role in inhibition of AML apoptosis and in cell survival. We provide evidence that ARC expression is regulated by MAPK and PI3K signaling. Inhibition of MAPK and PI3K pathways decreased ARC mRNA and protein levels in AML cells. ARC expression in AML cells is upregulated in co-cultures with bone marrow-derived mesenchymal stromal cells (MSCs) and the upregulation is suppressed in the presence of MAPK or PI3K inhibitors. To investigate the role of ARC in apoptosis resistance in AML, we generated stable ARC overexpressing (O/E) KG-1 and stable ARC knock down (K/D) OCI-AML3 and Molm13 cells and treated them with Ara-C and agents selectively inducing intrinsic (ABT-737) or extrinsic (TRAIL) apoptosis. We found that ARC O/E cells are more resistant and ARC K/D cells more sensitive to Ara-C, ABT-737, and TRAIL-induced apoptosis: EC50s of Ara-C, ABT-737, or TRAIL treatment at 48 hours for ARC O/E KG-1 and control cells were 1.5 ± 0.1 μM vs. 83.5 ± 4.6 nM, 2.2 ± 0.2 μM vs. 60.2 ± 3.1 nM, or 0.97 ± 0.03 μg/mL vs. 0.17 ± 0.08 μg/mL, respectively and for ARC K/D OCI-AML3 and control cells were 0.33 ± 0.02 μM vs. 3.4 ± 0.2 μM, 0.24 ± 0.01 μM vs. 1.3 ± 0.1 μM, or 0.13 ± 0.09 μg/mL vs. 0.36 ± 0.03 μg/mL, respectively. Bone marrow microenvironment is known to play critical roles in AML disease progression and in protecting leukemia cells from various therapeutic agent-induced apoptosis. Leukemia cells were co-cultured with MSCs in vitro study to mimic the in vivo condition. ARC was found to be highly expressed in MSCs and stable ARC K/D MSCs were generated. AML cell lines and primary patient samples were co-cultured with ARC K/D or control MSCs and treated with Ara-C, ABT-737, or TRAIL. Interestingly, ARC K/D MSCs lost their protective activity for leukemia cells treated with these agents. EC50s for OCI-AML3 cells co-cultured with ARC K/D or control MSCs for 48 hours treated with Ara-C, ABT-737, or TRAIL were 1.0 ± 0.04 μM vs. 4.5 ± 0.2 μM, 0.15 ± 0.06 μM vs. 0.53 ± 0.02 μM, or 1.4 ± 0.8 μg/mL vs. 8.1 ± 0.3 μg/mL, respectively. In addition, ARC O/E KG-1 cells grew faster and ARC K/D OCI-AML3 and Molm13 cells and ARC K/D MSCs grew slower than their respective controls. We then injected KG-1 cells into mice and found that NOD-SCID mice harboring ARC O/E KG-1 had significantly shorter survival than mice injected with the vector control KG-1 (median 84 vs. 111 days) as shown in the figure. Collectively, results demonstrate that ARC plays critical roles in AML. ARC is regulated by MSCs through various signaling pathways in AML cells, protects leukemia cells from apoptosis induced by chemotherapy and by agents selectively inducing intrinsic and extrinsic apoptosis. ARC regulates leukemia cell growth in vitro and in vivo. The results suggest that ARC is a potential target for AML therapy. In addition, targeting ARC in MSCs suppresses microenvironmental protection of AML cells. Disclosures: No relevant conflicts of interest to declare.

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Adipocytes Secrete Factors That Cause Leukemia Drug Resistance.

Blood ◽

10.1182/blood.v112.11.1346.1346 ◽

2008 ◽

Vol 112 (11) ◽

pp. 1346-1346

Author(s):

James W Behan ◽

Jason P Yun ◽

Marina P Proektor ◽

Ehsan A Ehsanipour ◽

Anna Butturini ◽

...

Keyword(s):

Bone Marrow ◽

Chemotherapy Resistance ◽

Leukemia Cell ◽

Conditioned Media ◽

Leukemia Cells ◽

Cell Contact ◽

Human Leukemia ◽

Bone Marrow Niche

Abstract We have previously shown that obesity is an independent predictor of leukemia relapse in children. We have also shown that obese mice transplanted with syngeneic leukemia cells have poorer survival after chemotherapy, even when they are dosed proportional to body weight. Since interactions between leukemia cells and cells of the bone marrow niche are considered important for chemotherapy resistance and relapse, and adipocytes can comprise ~50% of the bone marrow niche, we developed in vivo and in vitro models to investigate the role of adipocytes in the leukemia microenvironment. Obese C57Bl/6J mice were transplanted with GFP+ murine preB cell ALL (“8093”) cells and then treated with vincristine (0.5 mg/kg/week × 3 weeks). At the time of relapse, we found that GFP+ leukemia cells persisted in the fat pads of the mice. We then developed an in vitro co-culture system in which human or murine leukemia cells were cultured together with adipocytes (differentiated 3T3-L1s). Undifferentiated 3T3-L1 cells, which are fibroblastic in nature, were used as a control. In this model, adipocytes severely diminished the anti-leukemic effect of all chemotherapeutics tested against murine 8093 cells, including vincristine, dexamethasone, nilotinib, daunorubicin, and L-asparaginase. Adipocytes also protected murine T-cell ALL and human SD-1, RCH-ACV, and BV173 cells from vincristine and daunorubicin. Adipocyte protection of leukemia cells occurred independent of cell contact. Further experiments demonstrated that media conditioned by adipocytes was able to protect 8093 cells from a 3-day exposure to 25 nM dexamethasone (viable cells were at 40±12% of their plated value in regular media, 66±17% in fibroblast-conditioned media, and 109±24% in adipocyte-conditioned media, p<0.05). Surprisingly, adipocyte-conditioned media did not protect leukemia cells from daunorubicin. However, media conditioned by the presence of both adipocytes and leukemia cells simultaneously conferred a high degree of resistance to the leukemia cells (n=3, p<0.05 compared to all other media types). In summary, adipose tissue is a reservoir for relapsed leukemia cells in vivo. Adipocytes engender protection from multiple chemotherapies in murine and human leukemia cell lines. Adipocytes secrete factor(s) that confer dexamethasone and daunorubicin resistance to leukemia cells, though for the latter drug it appears that a two-way communication between leukemia and adipocytes may be necessary for this protection. Figure Figure

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TGF-β Neutralizing Antibody 1D11 Inhibits LIF-JAK-Stat3 Signaling and Enhances Cytarabine Induced Apoptosis in AML Cells in Bone Marrow Microenvironment

Blood ◽

10.1182/blood.v118.21.926.926 ◽

2011 ◽

Vol 118 (21) ◽

pp. 926-926

Author(s):

Yoko Tabe ◽

Yuexi Shi ◽

Zhihong Zeng ◽

Linhua Jin ◽

Yixin Zhou ◽

...

Keyword(s):

Bone Marrow ◽

Stromal Cells ◽

Molecular Mechanisms ◽

Leukemia Cell ◽

Neutralizing Antibody ◽

Leukemia Cells ◽

U937 Cells ◽

Induced Apoptosis ◽

Cells Cultured

Abstract Abstract 926 We have previously reported pro-survival effects of TGF-β1 in myelo-monocytic leukemia cells (Xu et al.,Br J Haematol.2008). Hypoxia and interactions with bone marrow (BM) stromal cells have emerged as essential components of leukemic BM microenvironment that promote leukemia cell survival and chemoresistance. Our preliminary data indicate that TGF-β neutralizing antibody 1D11 (Genzyme) prevents accumulation of AML cells in a quiescent G0 state under co-culture condition with BM-derived mesenchymal stromal cells (MSC) (Jin et al., ASH abstract 2010). In turn, the chemokine CXCL12 and its receptor CXCR4 play crucial roles in cell migration and stroma/leukemia cell interactions. In this study, we investigated the anti-leukemic effects and molecular mechanisms of action of TGF-β neutralizing antibody 1D11 under hypoxic conditions. We further investigated the anti-leukemic efficacy of 1D11 combined with CXCR4 antagonist plerixafor in the in vivo leukemia models. AML cells (MV4;11 and U937) were propagated under 1% O2 for at least 14 days to assure their sustained proliferation and survival. Isotype control antibody 13C4 combined with ara-C induced no significant change in apoptosis or cell cycle progression. In MV4;11 cells cultured with 2ng/mL rhTGF-β1, 1D11 (10 μg/mL) induced only minimal apoptosis by itself, yet enhanced low-dose cytarabine (AraC, 0.5 μM) induced apoptosis. This effect was more prominent under hypoxia compared to normoxia (% of subG1 fraction, 21% O2: ara-C, 2.6 ± 0.2%, ara-C + 1D11, 10.8 ± 2.5%, p=0.03; 1% O2: ara-C, 11.3 ± 2.7%, AraC + 1D11, 21.4 ± 0.5%, p=0.001). 1D11 with ara-C abrogated rhTGFβ1-induced accumulation of cells in G0/G1 phase (21% O2; cont, 73.8 ± 4.1, rhTGFβ, 82.2 ± 3.2, rhTGFβ + AraC, 65.4 ± 2.5, rhTGFβ + AraC + 1D11, 50.3 ± 1.9, p=0.001: in 1% O2; cont, 71.8 ± 1.3, rhTGFβ, 85.4 ± 1.4, rhTGFβ + AraC, 79.3 ± 5.1, rhTGFβ + AraC + 1D11, 67.1 ± 4.0, p = 0.03). The anti-leukemic efficacy of 1D11 was next examined in an in vivo leukemia model. 1D11 administered at 5 mg/kg IP every other day in combination with ara-C (50 mg/kg IP weekly) decreased leukemia burden of nude mice injected with Baf3/ITD-luciferase leukemia cells (p=0.002). Administration of small molecule CXCR4 inhibitor plerixafor, which successfully diminished cell migration to CXCL12 in vitro, in combination with 1D11 decreased leukemia burden in vivo (p=0.05), and co-administration of ara-C, plerixafor and 1D11 was most effective (bioluminescence intensity, ×107 photons/sec) control, 1.2 ± 0.2; ara-C, 0.94 ± 0.3; plerixafor + 1D11, 0.56 ± 0.1; plerixafor + 1D11 + ara-C, 0.23 ± 0.09, p=0.003). We next examined the molecular mechanisms responsible for chemosensitization through blockade of TGFβ with 1D11. Treatment with rhTGF-β1 induced upregulation of p21 expression as well as pro-survival phosphorylation of Stat3 in MV4;11 and U937 cells, and these effects were abrogated by 1D11. Knock-down of Stat3 by siRNA increased apoptosis induction in U937 cells cultured in the presence of rhTGFβ1. Notably, 4-fold upregulation of the established TGFβ target, leukemia inhibitory factor (LIF) gene mRNA, was observed after rhTGF-β1 treatment and this was reversed by 1D11. These results indicate that 1D11 inhibits rhTGF-β1-induced autocrine stimulation of pro-survival LIF-JAK-Stat3 signal transduction pathway in AML cells. In summary, blockade of TGF-β by 1D11, and abrogation of CXCL12/CXCR4 signaling may enhance the efficacy of chemotherapy against AML cells in the hypoxic BM microenvironment. These findings warrant further investigations in human clinical trials. Disclosures: Konopleva: Genzyme: Research Funding.

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Eptifibatide Reduced Cell Adhesion and Recruitment Of The Myeloid Sarcoma-Inducing Leukemia Cells

Blood ◽

10.1182/blood.v122.21.4220.4220 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4220-4220

Author(s):

Jen-Fen Fu ◽

Lee-Yung Shih

Keyword(s):

Bone Marrow ◽

Cell Adhesion ◽

Leukemia Cell ◽

Myeloid Sarcoma ◽

Leukemia Cells ◽

Antiplatelet Drug ◽

Ras Gene ◽

Cell Cell

AML patients with myeloid sarcoma (MS) usually had a poor outcome. Our clinical data revealed that AML patients harboring MLL/AF10 and RAS gene mutations were associated with MS formation. By using retroviral transduction/transplantation assay, we demonstrated that the mice transplanted with bone marrow (BM) cells carrying cooperating MLL/AF10(OM-LZ) and KRAS-G12C mutations induced MPD-like myeloid leukemia and MS. Gene expression analyses identified Gpr125, an adhesion G protein-coupled receptor, was up-regulated in the cells carrying cooperating mutations than the cells carrying MLL/AF10(OM-LZ) alone. Knockdown of Gpr125 by RNA interference reduced the number and the size of MS, suggesting that Gpr125 was involved in the MS formation. As Gpr125 contains a HormR domain with Lysine-Glycine-Aspartic acid (KGD) motif which is known to involve in the cell-extracellular matrix (ECM) and cell-cell adhesion, we investigated whether a cyclic RGD peptide drug, eptifibatide (Ep), could interfere MS formation. An in vitro cell-ECM binding assay showed that Gpr125 interacted with fibronectin. Ep reduced leukemia cell-fibronectin binding. Ep also reduced homotypic leukemia cell adhesion and leukemia cell-adipocyte adhesion. In vivo assay demonstrated that Ep reduced leukemia cells recruitment to the adipose tissues, spleen and bone marrow. Our results suggested that blocking Gpr125-mediated cell-ECM and cell-cell adhesion might be helpful to interfere MS formation and BM/spleen recruitment of leukemia cells. Disclosures: Off Label Use: Eptifibatide (Integrilin, Millennium Pharmaceuticals, also co-promoted by Schering-Plough/Essex), is an antiplatelet drug of the glycoprotein IIb/IIIa inhibitor class.

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Disulfiram, an clinically used anti-alcoholism drug has the potential to target acute myeloid leukemia cells in a copper-dependent manner in vivo

Blood ◽

10.1182/blood.v122.21.5040.5040 ◽

2013 ◽

Vol 122 (21) ◽

pp. 5040-5040

Author(s):

Bing Xu ◽

Rongwei Li ◽

Huijuan Dong ◽

Feili Chen ◽

Yuejian Liu ◽

...

Keyword(s):

Bone Marrow ◽

Acute Myeloid Leukemia ◽

Myeloid Leukemia ◽

Specific Antigen ◽

Leukemia Cell ◽

Leukemia Cells ◽

Control Group ◽

Acute Myeloid

Abstract Background Disulfiram(DS), an old drug clinically used for alcoholism, was reported to have antitumor effects, recent studies have found that Copper(Cu) can significantly enhance the DS-induced cell death in vitro in a variety of tumor cells. Our previous studies also demonstrated that disulfiram/copper (DS/Cu) couldtarget human leukemia cell lines(like KG1α,Molt4) through the activation of JNK, in vitro. However, there is few report about the ability of DS/Cu in killing cancer cells in vivo. Aims This study aims to explore the effect of DS/Cu on acute myeloid leukemia cell line KG1αin vivo and clarify the underlining mechanism. Methods 6-8 week old female NOD/SCID mice were sublethally irradiated with 2Gy X-ray the day before transplantation, followed by intravenous injection of KG1α cells (1×107 cells) suspended in 0.2 mL of PBS. 5 weeks after transplantation mice were randomly divided into three treatment groups: vehicle (0.9% saline), a combination of DS and Cu daily for 2 weeks, Ara-C alone twice before killing. Mice were sacrificed after 2 weeks treatment with tissues of spleen, liver, bone marrow being observed using histopathology method to detect the invasion of leukemia. The DS/Cu-induced p-c-jun activation was also examined by western blot using tissues of spleen, liver, bone marrow. Statistical analysis was carried out with one-way ANOVA to assess statistical significance (*p < 0.05). Results 4 weeks after transplantation, mice were dispirited with low appetite, down-bent gait, wrinkled fur, slow move, just like suffered from leukemia. What’s more, immature blasts like morphology similar to KG1α were found in the peripheral blood of the mice(11%±3.41). All the mice were sacrificed after 2 weeks treatment, mice in control group were observed with slightly larger spleen and liver with the morphology of invasion of leukemia such as a granular appearance than the other two groups. Histopathology examination showed that leukemia cells infiltrate liver, spleen and bone marrow, and the immunohistochemistry examination found that the leukemia cells in spleen, liver and bone marrow expressed human specific antigen CD45 with the highest expression level in the control group. Moreover, solid tumor could be observed in the peritoneal cavity of two mice in the control group with expression of human specific antigen CD45detected by immunohistochemistry examination. Western blot in this study showed DS/Cu complex induced phosphorylation of c-Jun expression in the spleen, liver and bone marrow. Conclusion DS/Cu complex could effectively target the acute myeloid leukemia cells in the acute leukemia NOD/SCID mice while inhibiting the invasion of leukemia to some extent, and the activation of JNK might play a functional role in DS/Cu mediated antileukemic effects. Disclosures: No relevant conflicts of interest to declare.

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Massive Mobilization of AML Cells into Circulation by Disruption of Leukemia/Stroma Cell Interactions Using CXCR4 Antagonist AMD3100: First Evidence in Patients and Potential for Abolishing Bone Marrow Microenvironment-Mediated Resistance.

Blood ◽

10.1182/blood.v108.11.568.568 ◽

2006 ◽

Vol 108 (11) ◽

pp. 568-568 ◽

Cited By ~ 12

Author(s):

Michael Andreeff ◽

Sergej Konoplev ◽

Rui-Yu Wang ◽

Zhihong Zeng ◽

Teresa McQueen ◽

...

Keyword(s):

Bone Marrow ◽

Leukemia Cell ◽

Surface Expression ◽

Bone Marrow Microenvironment ◽

Leukemic Cells ◽

Fish Analysis ◽

Cxcr4 Antagonist ◽

Induced Apoptosis

Abstract The chemokine receptor CXCR4 is critically involved in migration of hematopoietic cells to the stromal derived factor (SDF-1α)-producing bone marrow microenvironment. CXCR4 is regulated in part by mutant FLT3 signaling, but in a series of 122 AML samples with diploid karyotype and lack of FLT3 mutation (ITD), high CXCR4 expression negatively correlated with DFS and OS (p=0.03 and p=0.04, respectively), after multivariate analysis (Konoplev, ASH 2006). We hypothesized that inhibition of SDF-1α-/CXCR4 interactions would result in mobilization of leukemic blasts from the bone marrow into circulation. The in vivo effect of the CXCR4 antagonist AMD3100 was studied in three patients with AML, who had insufficient mobilization of CD34+ cells for autologous stem cell transplantation with G-CSF and/or cytoxan. The combination of G-CSF (10 μg/kg QD) and AMD3100 (240 μg/kg QD SC starting on d4 and repeated for 3–4 days) resulted in massive mobilization of leukemic cells into the circulation in a time-dependent fashion, as determined by flow cytometry and interphase FISH analysis of their respective cytogenetic abnormalities. Patient # Cytogenetics % (+) cells % (+) cells Apheresis FCM Day 2 Day 4/5 CD34x106/kg 1 Trisomy 21 22.6 57.0 FCM CD7/33 22.0 2 Trisomy 9 28.6 68.6 Inv 16 29.0 75.8 4.8 FCM CD13/33 74.0 3 Mono 17 40.4 53.4 5q31 37.5 49.6 8.7 FCM CD13/33 50.0 We and others have previously demonstrated that stroma/leukemia interactions mediate protection of leukemic cells from chemotherapy-induced apoptosis (Konopleva et al, Leukemia2002:1713). We then tested the hypothesis that CXCR4 inhibition would result in increased sensitivity to chemotherapy, using AMD3465, the second generation small-molecule CXCR4 inhibitor with greater potency than AMD3100. Results demonstrate inhibition of surface expression of CXCR4 and of SDF-1α-, and stroma(MS-5)-induced migration of AML cells. In vitro co-culture systems with stromal cells significantly protected leukemic cells (p < 0.01), while AMD3465 decreased stroma-mediated protection from AraC and Busulfan apoptosis and downregulated AKT signaling in AML cells. In a murine model of luciferase labeled Baf-FLT3ITD leukemias, AMD3465 induced massive dissemination of leukemia, which was abrogated by treatment with Sorafenib, a potent FLT3ITD inhibitor (Zhang, ASH 2006). Taken together, our data suggest that SDF-1α/CXCR4 interactions contribute to the resistance of leukemic cells to chemotherapy-induced apoptosis. Disruption of these interactions by CXCR4 inhibition results in leukemia dissemination and chemosensitization. Our results in leukemia patients provide first in man proof-of principle for a novel strategy of targeting the leukemia cell/bone marrow microenvironment interactions. A clinical trial testing this concept in patients with AML is under development.

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Hemangioblastic Activity of Infant Leukemia with t(4;11).

Blood ◽

10.1182/blood.v110.11.4279.4279 ◽

2007 ◽

Vol 110 (11) ◽

pp. 4279-4279

Author(s):

Zhongbo Hu ◽

Xiaomiao Li ◽

William B. Slayton

Keyword(s):

Bone Marrow ◽

Blood Vessels ◽

Cell Lines ◽

Leukemia Cell ◽

Scid Mice ◽

Leukemia Cells ◽

Leukemia Cell Lines ◽

Infant Leukemia

Abstract Background: Infant leukemia patients with t(4;11) have an extremely high risk for treatment failure. Hemangioblasts are cells that were initially described in the embryonic yolk sac, where they make both blood and blood vessels when these two systems are forming. It was demonstrated that hemangioblasts are present in the adult bone marrow and CML patients. Recently, subgroups of infant ALL patients with t(4;11) were found to have gene expression profiles similar to hemangioblasts by microarray. However, whether infant leukemia cells behave like hemangioblasts and produce their own blood vessels remains unknown. Objective: We sought to determine whether infant leukemia cells with t(4;11) are derived from malignant hemangioblasts and can produce their own blood vessels. Design/Methods: Three childhood leukemia cell lines with t(4;11): MV4-11, SEM-K2 and RS4-11, were used to analyze the expression pattern of key angiogenic receptors by flow cytometry and angiogenesis related proteins by protein array in comparison with benign endothelial cells. These cell lines were also cultured in vitro using Matrilgel, an in vitro angiogenesis assay system, in order to test their ability to produce vascular tubes. These cell lines were injected into the immune deficient NOD/SCID mice after sublethal irradiation to establish leukemia in vivo. Some of primary cells from MLL patients were obtained and subcutaneously injected into NOD/SCID mice mixed with BD Matrigel to observe their vessel development in vivo together with these three cell lines. The bone marrow, liver, spleen and tumor tissues together with Matrigel were collected to look for the evidence of t(4;11) in endothelial cells by immunohistochemical staining and fluorescent in situ hybridization (FISH). Results: The leukemia cell lines expressed many angiogenetic cytokines, such as VEGF, VEGF-D, RANTES, PIGF, PDGF-BB, MCP-1, IGF-1, ENA-78, and angiogenin, at the same levels as HUVEC cells, a human umbilical vessel endothelial cell line. Different cell lines expressed some angiogenesis-related receptors, such as CD31, Tie-2, PDGFRalpha, CD141, CD146, and KDR. None of the cell lines formed tubes in Matrigel. When these three cell lines generated leukemia in NOD/SCID mice, the microvessel density level increased in the tumor areas. However, immunostaining for human and murine endothelial markers demonstrated that all the vessels came from the mouse, not from the human leukemia cells. Conclusions: We conclude that infant leukemia cell lines with t(4;11) have proangiogenesic activity. However, these cells do not function as hemangioblasts, as they do not produce blood vessels in culture or in vivo in NOD/SCID mice. We plan to look further by examing bone marrow biopsies from patients with t(4;11) leukemia to determine whether the translocation is present in their blood vessels.

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In Vivo RNA Interference Screening Identifies a Leukemia-Specific Dependence on Integrin Beta 3 Signaling

Blood ◽

10.1182/blood.v118.21.758.758 ◽

2011 ◽

Vol 118 (21) ◽

pp. 758-758

Author(s):

◽

Fatima Al-Shahrour ◽

Kimberly A. Hartwell ◽

Lisa P Chu ◽

Jaras Marcus ◽

...

Keyword(s):

Rna Interference ◽

Cell Growth ◽

Leukemia Cell ◽

Leukemia Cells ◽

Growth And Survival ◽

Integrin Beta 3 ◽

Shrna Screen ◽

Primary Leukemia

Abstract Abstract 758 Primary leukemia stem cells (LSCs) reside in an in vivo microenvironment that supports the growth and survival of malignant cells. Despite the increasing understanding of the importance of niche interactions and primary cell biology in leukemia, many studies continue to focus on cell autonomous processes in artificial model systems. The majority of strategies to-date that attempt to define therapeutic targets in leukemia have relied on screening cell lines in culture; new strategies should incorporate the use of primary disease within a physiologic niche. Using a primary murine MLL-AF9 acute myeloid leukemia (AML) model highly enriched for LSCs, we performed an in vivo short hairpin RNA (shRNA) screen to identify novel genes that are essential for leukemia growth and survival. LSCs infected with pools of shRNA lentivirus were transplanted and grown in recipient mice for 2 weeks, after which bone marrow and spleen cells were isolated. Massively parallel sequencing of infected LSCs isolated before and after transplant was used to quantify the changes in shRNA representation over time. Our in vivo screens were highly sensitive, robust, and reproducible and identified a number of positive controls including genes required for MLL-AF9 transformation (Ctnnb1, Mef2c, Ccna1), genes universally required for cell survival (Ube2j2, Utp18), and genes required in other AML models (Myb, Pbx1, Hmgb3). In our primary and validation screens, multiple shRNAs targeting Integrin Beta 3 (Itgb3) were consistently depleted by more than 20-fold over two weeks in vivo. Follow up studies using RNA interference (RNAi) and Itgb3−/− mice identified Itgb3 as essential for murine leukemia cells growth and transformation in vivo, and loss of Itgb3 conferred a statistically significant survival advantage to recipient mice. Importantly, neither Itgb3 knockdown or genetic loss impaired normal hematopoietic stem and progenitor cell (HSPC) function in 16 week multilineage reconstitution assays. We further identified Itgav as the heterodimeric partner of Itgb3 in our model, and found that knockdown of Itgav inhibited leukemia cell growth in vivo. Consistent the therapeutic aims or our study, flow cytometry on primary human AML samples revealed ITGAV/ITGB3 heterodimer expression. To functionally assess the importance of gene expression in a human system, we performed another RNAi screen on M9 leukemia cells, primary human cord blood CD34+ cells transduced with MLL-ENL that are capable of growing in vitro or in a xenotransplant model in vivo. We found that ITGB3 loss inhibited M9 cell growth in vivo, but not in vitro, consistent with the importance of ITGB3 in a physiologic microenvironment. We explored the signaling pathways downstream of Itgb3 using an additional in vivo, unbiased shRNA screen and identified Syk as a critical mediator of Itgb3 activity in leukemia. Syk knockdown by RNAi inhibited leukemia cell growth in vivo; downregulation of Itgb3 expression resulted in decreased levels of Syk phosphorylation; and expression of an activated form of Syk, TEL-SYK, rescued the effects of Itgb3 knockdown on leukemia cell growth in vivo. To understand cellular processes controlled by Itgb3, we performed gene expression studies and found that, in leukemia cells, Itgb3 knockdown induced differentiation and inhibited multiple previously published LSC transcriptional programs. We confirmed these results using primary leukemia cell histology and a model system of leukemia differentiation. Finally, addition of a small molecule Syk inhibitor, R406, to primary cells co-cultured with bone marrow stroma caused a dose-dependent decrease in leukemia cell growth. Our results establish the significance of the Itgb3 signaling pathway, including Syk, as a potential therapeutic target in AML, and demonstrate the utility of in vivo RNA interference screens. Disclosures: Armstrong: Epizyme: Consultancy.

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Curcumin and Its Analogue Induce Apoptosis in Leukemia Cells and Have Additive Effects with Bortezomib in Cellular and Xenograft Models

BioMed Research International ◽

10.1155/2015/968981 ◽

2015 ◽

Vol 2015 ◽

pp. 1-11 ◽

Cited By ~ 16

Author(s):

L. I. Nagy ◽

L. Z. Fehér ◽

G. J. Szebeni ◽

M. Gyuris ◽

P. Sipos ◽

...

Keyword(s):

Leukemia Cell ◽

Leukemic Cells ◽

Leukemia Cell Line ◽

Leukemia Cells ◽

Great Promise ◽

Human Leukemia ◽

Human Leukemia Cell Line ◽

Apoptotic Effects

Combination therapy of bortezomib with other chemotherapeutics is an emerging treatment strategy. Since both curcumin and bortezomib inhibit NF-κB, we tested the effects of their combination on leukemia cells. To improve potency, a novel Mannich-type curcumin derivative, C-150, was synthesized. Curcumin and its analogue showed potent antiproliferative and apoptotic effects on the human leukemia cell line, HL60, with different potency but similar additive properties with bortezomib. Additive antiproliferative effects were correlated well with LPS-induced NF-κB inhibition results. Gene expression data on cell cycle and apoptosis related genes, obtained by high-throughput QPCR, showed that curcumin and its analogue act through similar signaling pathways. In correlation with in vitro results similar additive effect could be obsereved in SCID mice inoculated systemically with HL60 cells. C-150 in a liposomal formulation given intravenously in combination with bortezomib was more efficient than either of the drugs alone. As our novel curcumin analogue exerted anticancer effects in leukemic cells at submicromolar concentration in vitro and at 3 mg/kg dose in vivo, which was potentiated by bortezomib, it holds a great promise as a future therapeutic agent in the treatment of leukemia alone or in combination.

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Combined Use of Dendritic Cells Enhances Specific Anti-Leukemia Effect of Leukemia Cell-Derived-HSP70 in a Mouse Model with Minimal Residual Leukemia Cells.

Blood ◽

10.1182/blood.v104.11.3065.3065 ◽

2004 ◽

Vol 104 (11) ◽

pp. 3065-3065

Author(s):

Kazuya Sato ◽

Yoshihiro Torimoto ◽

Yasuyuki Iuchi ◽

Yasuaki Tamura ◽

Junko Jimbo ◽

...

Keyword(s):

Bone Marrow ◽

Dendritic Cells ◽

Bone Marrow Cells ◽

Leukemia Cell ◽

Class I ◽

Biochemical Data ◽

Leukemia Cells ◽

Combined Use ◽

Minimal Residual

Abstract Background: Heat shock proteins (HSPs) are molecular chaperones binding a broad repertorie of endogenous antigenic peptides and carrying them to the MHC. Because the identification of each tumor specific antigen is not necessary, the immunotherapy using HSPs is more practical than other immunological procedures. Meanwhile, relapse due to minimal residual disease (MRD) is a big problem of autologous stem cell transplantation (SCT) against leukemia. We previously reported that immunotherapy using leukemia cell-derived HSPs is effective against MRD after syngeneic bone marrow transplantation (BMT) in mice (Sato et al. Blood, 2001). However, patients receiving SCT are usually immunocompromised due to repeated anti-cancer therapies. Accordingly, it is important to enhance the cytotoxicities (CTXs) against leukemia. Dendritic cells (DCs) are known as professional antigen-presenting cells with a specific receptor for HSPs and are expected to play a major role in immunotherapy. In this study, we evaluated whether the vaccination of DCs pulsed with HSP70 enhances the anti-leukemia effect induced by leukemia cell-derived HSP70 after syngeneic BMT and evaluated the safety of this immunotherapy. Methods: Three class-I-identical mouse tumor cell lines (A20: B-cell leukemia; T27A: myeloid leukemia; colo26: colonic carcinoma) and syngeneic balb/c mice were used in this study. HSP70 was purified from tumor cells. DCs were generated from bone marrow cells cultured with GM-CSF. DCs were pulsed with HSP70 (HSP70-pulsed-DCs) in vitro. Mice were received total body irradiation (TBI) and transplanted bone marrow cells after TBI, then inoculated 2.5 x 104 A20 cells intravenously. HSP70 or HSP70-pulsed-DCs was subcutaneously administrated. Survival days of immunized mice were compared using Kaplan and Meier methods. CTXs of splenocytes against A20 cells were determined by 51Cr release assay. Histological findings of liver and knee joint and biochemical data of serum of immunized mice were investigated. Results: All mice without immunization or immunized with DCs alone died from leukemic dissemination within 90 days after A20 inoculation, whereas mice immunized with A20-derived HSP70 (A20-HSP70) or A20-HSP70-pulsed-DCs survived long significantly. Additionally, although only 60% of the mice immunized with A20-HSP70 survived on day 120, all the mice immunized with A20-HSP70-pulsed-DCs survived with no residual leukemia cells over 120 days. Moreover, splenocytes of mice immunized with A20-HSP70-pulsed-DCs showed significantly higher CTXs against A20 cells in vitro compare to those with A20-HSP70 alone. However, no CTXs against A20 cells were induced by immunization with colo26-or T27A-HSP70-pulsed-DCs. These CTXs against A20 cells were significantly blocked by anti-CD8 and anti-MHC class-I, but not by anti-CD4. Additionally, no abnormal findings were detected either in biochemical data of serum or in histopathology of liver and joint tissue in long term immunized mice. Conclusions: Combined use of dendritic cells with leukemia cell-derived HSP70 enhances anti-leukemia effect by inducing specific cytotoxic activities against leukemia cells, and eradicates MRD effectively and safely even for immunocompromised status after syngeneic BMT. This approach would be useful for a further application of HSP in leukemia-patients after autologous SCT.

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Flt3 Ligand Negatively Regulates In Vitro Migration, Intracellular Signaling Activated by SDF-1α/CXCR4 and In Vivo Homing of Hematopoietic Progenitor Cells.

Blood ◽

10.1182/blood.v104.11.2674.2674 ◽

2004 ◽

Vol 104 (11) ◽

pp. 2674-2674

Author(s):

Seiji Fukuda ◽

Hal E. Broxmeyer ◽

Louis M. Pelus

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Hematopoietic Progenitor Cells ◽

Leukemia Cells ◽

Flt3 Ligand ◽

Hematopoietic Progenitor ◽

Short Term ◽

Hematopoietic Stem

Abstract The Flt3 receptor tyrosine kinase (Flt3) is expressed on primitive normal and transformed hematopoietic cells and Flt3 ligand (FL) facilitates hematopoietic stem cell mobilization in vivo. The CXC chemokine SDF-1α(CXCL12) attracts primitive hematopoietic cells to the bone marrow microenvironment while disruption of interaction between SDF-1α and its receptor CXCR4 within bone marrow may facilitate their mobilization to the peripheral circulation. We have previously shown that Flt3 ligand has chemokinetic activity and synergistically increases migration of CD34+ cells and Ba/F3-Flt3 cells to SDF-1α in short-term migration assays; this was associated with synergistic phosphorylation of MAPKp42/p44, CREB and Akt. Consistent with these findings, over-expression of constitutively active ITD (internal tandem duplication) Flt3 found in patients with AML dramatically increased migration to SDF-1α in Ba/F3 cells. Since FL can induce mobilization of hematopoietic stem cells, we examined if FL could antagonize SDF-1α/CXCR4 function and evaluated the effect of FL on in vivo homing of normal hematopoietic progenitor cells. FL synergistically increased migration of human RS4;11 acute leukemia cells, which co-express wild-type Flt3 and CXCR4, to SDF-1α in short term migration assay. Exogenous FL had no effect on SDF-1α induced migration of MV4-11 cells that express ITD-Flt3 and CXCR4 however migration to SDF-1α was partially blocked by treatment with the tyrosine kinase inhibitor AG1296, which inhibits Flt3 kinase activity. These results suggest that FL/Flt3 signaling positively regulates SDF-1α mediated chemotaxis of human acute leukemia cells in short-term assays in vitro, similar to that seen with normal CD34+ cells. In contrast to the enhancing effect of FL on SDF-1α, prolonged incubation of RS4;11 and THP-1 acute myeloid leukemia cells, which also express Flt3 and CXCR4, with FL for 48hr, significantly inhibited migration to SDF-1α, coincident with reduction of cell surface CXCR4. Similarly, prolonged exposure of CD34+ or Ba/F3-Flt3 cells to FL down-regulates CXCR4 expression, inhibits SDF-1α-mediated phosphorylation of MAPKp42/p44, CREB and Akt and impairs migration to SDF-1α. Despite reduction of surface CXCR4, CXCR4 mRNA and intracellular CXCR4 in Ba/F3-Flt3 cells were equivalent in cells incubated with or without FL, determined by RT-PCR and flow cytometry after cell permeabilization, suggesting that the reduction of cell surface CXCR4 expression is due to accelerated internalization of CXCR4. Furthermore, incubation of Ba/F3-Flt3 cells with FL for 48hr or over-expression of ITD-Flt3 in Ba/F3 cells significantly reduced adhesion to VCAM1. Consistent with the negative effect of FL on in vitro migration and adhesion to VCAM1, pretreatment of mouse bone marrow cells with 100ng/ml of FL decreased in vivo homing of CFU-GM to recipient marrow by 36±7% (P<0.01), indicating that FL can negatively regulate in vivo homing of hematopoietic progenitor cells. These findings indicate that short term effect of FL can provide stimulatory signals whereas prolonged exposure has negative effects on SDF-1α/CXCR4-mediated signaling and migration and suggest that the FL/Flt3 axis regulates hematopoietic cell trafficking in vivo. Manipulation of SDF-1α/CXCR4 and FL/Flt3 interaction could be clinically useful for hematopoietic cell transplantation and for treatment of hematopoietic malignancies in which both Flt3 and CXCR4 are expressed.

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