scholarly journals Flt3/ITD Confers Resistance to FLT3 Inhibitor AC220 By up-Regulating Runx1

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2223-2223
Author(s):  
Tomohiro Hirade ◽  
Mariko Abe ◽  
Chie Onishi ◽  
Seiji Yamaguchi ◽  
Seiji Fukuda
Keyword(s):  
Tyrosine Kinase ◽  
Prolonged Exposure ◽  
Kinase Inhibitor ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Specific Inhibitor ◽  
Hematopoietic Stem ◽  
Runx1 Expression ◽  
Cells Cultured ◽  
Resistant Cells

Abstract FMS-like tyrosine kinase 3 (FLT3) is a membrane type tyrosine kinase and has important roles for the proliferation and differentiation of the hematopoietic cells. The Internal Tandem Duplications of FLT3 (FLT3/ITD) is detected in approximately 30 % of patients with acute myeloid leukemia (AML) and the prognoses of FLT3/ITD+ AML are very poor. While a number of inhibitors targeting FLT3 tyrosine kinase have been developed, few drugs are effective for the FLT3/ITD+ AML because of emergence of resistant cells against the drugs. Recently, AC220 (Quizartinib), a second generation class III tyrosine kinase inhibitor (TKI) for FLT3/ITD+ AML was developed and used in clinical trials. Although AC220 is a more potent and specific inhibitor for FLT3/ITD compared to the other TKIs, report demonstrates that prolonged exposure to AC220 can generate resistant clones to AC220 in FLT3/ITD+ cells (Smith et al. Nature 2012). These findings underscore the need to develop additional therapeutic strategies to overcome the resistance of FLT3/ITD+ AML to TKIs. However, the mechanism responsible for drug resistance of FLT3/ITD+ AML cells remains to be investigated. We previously reported that mRNA expression of RUNX1, a core-binding transcription factor that regulates the differentiation and proliferation of hematopoietic stem cells, is significantly higher in FLT3/ITD+AML cells compared to FLT3/ITD-AML cells (Hirade et al. ASH 2013). Although loss of RUNX1 function (i.e. RUNX1/ETO fusion gene) contributes to the development of AML, RUNX1 also promotes survival of AML cells (Goyama et al. JCI 2013) and can function as an oncogene in cancer cells (Kilbey et al. Cancer Research 2010). These findings lead us hypothesize that RUNX1 may confer resistance of AML cells to TKIs. In the present study, we investigated if Runx1 is involved in the refractory phenotype of Flt3/ITD+cells to AC220. Transduction of Flt3/ITD into IL3-dependent mouse 32D cells allowed the cells proliferate in a growth factor independent fashion, concomitant with up-regulation of Runx1 mRNA level, similar to the patients’ samples with FLT3/ITD+AML. Silencing Runx1 expression using shRNA resulted in 70% reduction of Flt3/ITD+32D cells that proliferated in the absence of growth factors. Similarly, incubating the Flt3/ITD+32D cells with 0.5nM AC220 inhibited their factor independent proliferation by 95%, which was further accentuated up to 99% by the combination with shRNA mediated silencing of Runx1. Although the number of factor independent Flt3/ITD+32D cells cultured in the presence of 2nM AC220 rapidly declined within 96 hours, the residual cells subsequently re-proliferate within 14 days and became no longer sensitive to AC220. Surprisingly, the expression of Runx1 mRNA in the resistant cells to AC220 was 5.0±0.2 fold higher (P<0.05) compared to control Flt3/ITD+32D cells sensitive to AC220. Silencing Runx1 using shRNA abrogated the proliferation of AC220-resistant Flt3/ITD+32D cells cultured in the presence of 2nM AC220, leading to 99.5% reduction in the viable cells. Our data indicates that knocking down Runx1 expression enhances the cytotoxic effect of AC220 on Flt3/ITD+32D cells and that Runx1 expression is significantly up-regulated by the AC220 resistance cells. Moreover, Runx1 knockdown recovered the cytotoxicity of AC220 in the refractory Flt3/ITD+32D cells, demonstrating that Flt3/ITD confers resistance to AC220 by up-regulating the expression of Runx1. These findings demonstrate that antagonizing RUNX1 may represent potential therapeutic strategy in the patients with FLT3/ITD+ AML that become refractory to AC220. Disclosures No relevant conflicts of interest to declare.

Combination of Crenolanib with Sorafenib Produces Synergistic Pro-Apoptotic Effects in FLT3-ITD-Inhibitor-Resistant Acute Myelogenous Leukemias with FLT3 Mutations

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3591-3591 ◽  
Author(s):  
Chen Gao ◽  
Weiguo Zhang ◽  
Rodrigo Jacamo ◽  
Abhijit Ramachandran ◽  
Donald Small ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Cell Lines ◽  
Kinase Inhibitor ◽  
Conflicts Of Interest ◽  
Single Agent ◽  
Point Mutations ◽  
Type I ◽  
Type Ii ◽  
Apoptotic Effects ◽  
Resistant Cells

Abstract Abstract 3591 Activating mutations in the FLT3 gene, including internal tandem duplications (ITDs) and missense point mutations of the tyrosine kinase domain (TKD), are frequently observed in AML patients and confer poor prognosis (1). Targeting FLT3 ITD mutations using the multi-kinase inhibitor Sorafenib (a type II kinase inhibitor, which binds to inactive conformation of a kinase ATP pocket)(2) showed impressive anti-leukemia effects in FLT3-ITD mutated AML in Phase I/II clinical trials (3) However, resistance/relapse develops regularly during prolonged Sorafenib therapy (4), in part through acquired point mutations of TKD domains. We postulated that the conformational change of FLT3 protein resulting from acquired point mutations limits the accessibility of sorafenib and leads to resistance (5, 6). Recently, Crenolanib, a novel PDGFRβ tyrosine kinase inhibitor, showed impressive anti-tumor effects by targeting the active conformation of a kinase ATP pocket of FLT3 protein (a type I kinase inhibitor). Therefore, we hypothesize that targeting different sites of FLT3 protein simultaneously using different types of kinase inhbitors may be effective in overcoming sorafenib resistance. We here report that Crenolanib has anti-leukemic activity in Sorafenib-resistant cells which harbor both ITD and acquired TKD point mutations i, and that its combination with Sorafenib in Sorafenib-resistant cells exerts synergistic pro-apoptotic effects. The anti-leukemic activity of Crenolanib was assessed by measuring cell viability (trypan Blue exclusion) and apoptosis induction (annexin V/propidium iodide staining) in isogenic murine Ba/F3 AML cell lines with stable transfection of human FLT3-ITD mutations, in Sorafenib resistant Ba/F3-ITD-Res cells derived from long-term, low-dose exposure of Ba/F3-ITD to Sorafenib in vitro, which harbor N676D and Y842C mutations, and Sorafenib-resistant cell lines Ba/F3-ITD+676, Ba/F3-ITD+842 and Ba/F3-ITD+676/842 which carry ITD and TKD point mutations (N676D, Y842C and N676D/Y842C mutations, respectively). Effects of combinatorial regimen employing Crenolanib and Sorafenib were analyzed using CalcuSyn software (combination index (CI) : CI<1 = synergistic, CI>1 = antagonistic effects). Results show that single agent Crenolanib induced cell growth arrest in leukemia cells Ba/F3-ITD, Ba/F3-ITD+676, Ba/F3-ITD+842 and Ba/f3-ITD+842/676, at IC50s of 0.012, 0.012 0.037 and 0.038uM, respectively, and induced apoptosis (EC50s) at 0.17, 0.23, 0.19, and 0.22uM, respectively, after 72 hours of treatment. Western Blot showed that Crenolanib profoundly suppressed phosphorylation levels of FLT3 protein and its downstream targets ERK and AKT and induced cleavage of caspase 3. Sorafenib-resistant cells Baf3-ITD+Res and Baf3-ITD+842/676 (EC50s for Sorafenib were 4.2 ± 1.50 and 6.6 ± 0.53 μM, respectively) were exposed to submicromolar concentrations of Crenolanib and Sorafenib concomitantly for 48 h, resulting in impressive synergistic pro-apoptotic effects (CIs were 0.56 ± 0.12 and 0.36 ± 0.04, respectively), implying high synergistic potency of Type I and Type II FLT3 kinase inhibitors, when given concomitantly. In vivo experiments are in progress. Our findings provide therapeutic rationale for a combinatorial treatment strategy with Crenolanib and Sorafenib of FLT-ITD inhibitor-refractory AML. Disclosures: No relevant conflicts of interest to declare.

A Novel Compound Inhibits Chronic Myeloid Leukemia Via Upregulating Apoptosis

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5559-5559
Author(s):  
Jiajia Xin ◽  
Dandan Yin ◽  
Wei Fu ◽  
Hui-Jie Zhang ◽  
Yaozhen Chen ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Chronic Myeloid Leukemia ◽  
Tyrosine Kinase ◽  
Myeloid Leukemia ◽  
Kinase Inhibitors ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Leukemic Cells ◽  
Hematopoietic Stem

Abstract Chronic myeloid leukemia (CML) is a myeloid proliferative disorder mainly result from chimeric protein BCR-ABL1 encoded by a fusion gene at the t(9;22) (q34;q11) chromosomal translocation. Intrinsically, this recombined protein results in an increased tyrosine kinase (TK) activity that directly related to hematopoietic stem cell malignant proliferation. Consequently, the drugs derived from tyrosine kinase inhibitors (TKI) have been developed as an infective therapy, and greatly improved patients survival in clinic. Unfortunately, single TKI administration led to toxicities or tolerance in long-term treated CML patients. Even worse is, about 5% CML patients were not caused by bcr-abl gene mutation. Thus better medicines are badly needed to compensate CML therapy. Herein, we investigated the undefined function of a biscoumarins. The new synthesized compound exhibited a null toxicity on HUVECs but intensive toxicity on K562 leukemic cells. Subsequent results demonstrated that it efficiently inhibited the expansion of human CML cell line and bone marrow cells of SCL-tTA-BCL/ABL transgenic model mice via increased apoptosis. Critically, we also showed that CD34+ bone marrow leukemic cells collected from patients underwent more apoptosis after treated by the biscoumarins derivate. To extend these results into vivo, we observed a prolonged survival of bcr-abl transgenic mice treated by derivate mono-therapy or combination with imatinib compared to those of untreated or imatinib-treated CML mice. All together, these results indicated that this biscoumarins derivate may have novel potential as a therapeutic agent against CML. Disclosures No relevant conflicts of interest to declare.

scholarly journals Influence of FLT3-ITD Mutation and Length on the Treatment Response and Prognosis in Cytogenetically Normal AML Patients

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 5245-5245
Author(s):  
Xuejie Jiang ◽  
Changxin Yin ◽  
Junya Sun ◽  
Jiaying Cheng ◽  
Qiang Wang ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Treatment Response ◽  
Kinase Inhibitor ◽  
Conflicts Of Interest ◽  
Term Survival ◽  
Hematopoietic Stem ◽  
Relapse Risk ◽  
Increased Risk ◽  
Negative Effect

Abstract BACKGROUND : Mutations of internal tandem duplication in FMS-like tyrosine kinase 3 (FLT3-ITD) contributed to poor prognosis in cytogenetically normal acute myeloid leukemia (CN-AML). FLT3 tyrosine kinase inhibitor sorafenib in combination with chemotherapy was applied to treat FLT3-ITD AML patients with limited efficacy. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) was considered as a potent therapeutic regimen in FLT3-ITD patients, but additional sorafenib maintenance was indispensable to support their long-term survival after allo-HSCT. Studies showed that increasing ITD size may be accompanied with decreasing OS and RFS in AML patients, but it remained controversial about the prognostic implication of ITD mutant lengths, the prognostic influence was important to evaluate in determining the therapeutic strategy for AML patients with different ITD lengths. METHODS: Total 185 CN-AML patients with and without FLT3-ITD mutations were enrolled in this study. We retrospectively studied the clinical characteristic, treatment response, survival and relapse risk after chemotherapy or allo-HSCT plus sorafenib in these patients. Distribution of ITD lengths detected in AML patients suggested two groups including long (≥70bp) and short ITD length (<70bp). Influence of FLT3-ITD mutation and its length were investigated after chemotherapy or allo-HSCT plus sorafenib. RESULT: FLT3-ITD mutations were detected in 15 percentage of AML patients, and associated with leukocytosis, high blast percentage in bone morrow (BM) and increased risk of treatment failure. FLT3-ITD mutations indicated decreased complete remission (CR) rate, overall survival (OS) and relapse-free survival (RFS), and increased relapse risk (RR) in AML patients after chemotherapy plus sorafenib. Patients with long ITD length (≥70bp) had worse OS and RFS, and more relapse probability than these with short ITD length (< 0bp) or FLT3-WT, but patients with short ITD length and FLT3-WT had the similar RFS and RR after chemotherapy. Allo-HSCT plus sorafenib maintenance significantly prolonged OS and RFS, decreased RR in FLT3-ITD patients, especially in these with long ITD length instead of those with short ITD length. CONCLUSION: Our findings indicated that FLT3-ITD mutation and long ITD length had negative effect on treatment response and prognosis in CN-AML patients. Allo-HSCT plus sorafenib maintenance was an effective strategy to improve survival and decrease relapse probability, abrogated disadvantage from long ITD length in FLT3-ITD patients. Disclosures No relevant conflicts of interest to declare.

scholarly journals Mechanisms of Disease Progression and Resistance to Tyrosine Kinase Inhibitor Therapy in Chronic Myeloid Leukemia: An Update

2019 ◽  
Vol 20 (24) ◽  
pp. 6141 ◽  
Author(s):  
Luana Bavaro ◽  
Margherita Martelli ◽  
Michele Cavo ◽  
Simona Soverini
Keyword(s):  
Chronic Myeloid Leukemia ◽  
Tyrosine Kinase ◽  
Disease Progression ◽  
Myeloid Leukemia ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Fusion Gene ◽  
Primary Resistance ◽  
Secondary Resistance ◽  
Dismal Prognosis

Chronic myeloid leukemia (CML) is characterized by the presence of the BCR-ABL1 fusion gene, which encodes a constitutive active tyrosine kinase considered to be the pathogenic driver capable of initiating and maintaining the disease. Despite the remarkable efficacy of tyrosine kinase inhibitors (TKIs) targeting BCR-ABL1, some patients may not respond (primary resistance) or may relapse after an initial response (secondary resistance). In a small proportion of cases, development of resistance is accompanied or shortly followed by progression from chronic to blastic phase (BP), characterized by a dismal prognosis. Evolution from CP into BP is a multifactorial and probably multistep phenomenon. Increase in BCR-ABL1 transcript levels is thought to promote the onset of secondary chromosomal or genetic defects, induce differentiation arrest, perturb RNA transcription, editing and translation that together with epigenetic and metabolic changes may ultimately lead to the expansion of highly proliferating, differentiation-arrested malignant cells. A multitude of studies over the past two decades have investigated the mechanisms underlying the closely intertwined phenomena of drug resistance and disease progression. Here, we provide an update on what is currently known on the mechanisms underlying progression and present the latest acquisitions on BCR-ABL1-independent resistance and leukemia stem cell persistence.

Efficacy of STI571, an Abl tyrosine kinase inhibitor, in conjunction with other antileukemic agents against Bcr-Abl–positive cells

Blood ◽  
2000 ◽  
Vol 96 (9) ◽  
pp. 3195-3199 ◽  
Author(s):  
J. Tyler Thiesing ◽  
Sayuri Ohno-Jones ◽  
Kathryn S. Kolibaba ◽  
Brian J. Druker
Keyword(s):  
Clinical Trials ◽  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitor ◽  
Kinase Inhibitor ◽  
Single Agent ◽  
Myelogenous Leukemia ◽  
Hematopoietic Stem ◽  
Abl Tyrosine Kinase ◽  
Abl Tyrosine Kinase Inhibitor

Abstract Chronic myelogenous leukemia (CML), a malignancy of a hematopoietic stem cell, is caused by the Bcr-Abl tyrosine kinase. STI571(formerly CGP 57148B), an Abl tyrosine kinase inhibitor, has specific in vitro antileukemic activity against Bcr-Abl–positive cells and is currently in Phase II clinical trials. As it is likely that resistance to a single agent would be observed, combinations of STI571 with other antileukemic agents have been evaluated for activity against Bcr-Abl–positive cell lines and in colony-forming assays in vitro. The specific antileukemic agents tested included several agents currently used for the treatment of CML: interferon-alpha (IFN), hydroxyurea (HU), daunorubicin (DNR), and cytosine arabinoside (Ara-C). In proliferation assays that use Bcr-Abl–expressing cells lines, the combination of STI571 with IFN, DNR, and Ara-C showed additive or synergistic effects, whereas the combination of STI571 and HU demonstrated antagonistic effects. However, in colony-forming assays that use CML patient samples, all combinations showed increased antiproliferative effects as compared with STI571 alone. These data indicate that combinations of STI571 with IFN, DNR, or Ara-C may be more useful than STI571 alone in the treatment of CML and suggest consideration of clinical trials of these combinations.

scholarly journals The quiescent fraction of chronic myeloid leukemic stem cells depends on BMPR1B, Stat3 and BMP4-niche signals to persist in patients in remission

Haematologica ◽  
2020 ◽  
Vol 106 (1) ◽  
pp. 111-122 ◽  
Author(s):  
Sandrine Jeanpierre ◽  
Kawtar Arizkane ◽  
Supat Thongjuea ◽  
Elodie Grockowiak ◽  
Kevin Geistlich ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Tyrosine Kinase ◽  
Stromal Cells ◽  
Kinase Inhibitor ◽  
Bmp Signaling ◽  
Myelogenous Leukemia ◽  
Leukemic Stem Cells ◽  
Hematopoietic Stem

Chronic myelogenous leukemia arises from the transformation of hematopoietic stem cells by the BCR-ABL oncogene. Though transformed cells are predominantly BCR-ABL-dependent and sensitive to tyrosine kinase inhibitor treatment, some BMPR1B+ leukemic stem cells are treatment-insensitive and rely, among others, on the bone morphogenetic protein (BMP) pathway for their survival via a BMP4 autocrine loop. Here, we further studied the involvement of BMP signaling in favoring residual leukemic stem cell persistence in the bone marrow of patients having achieved remission under treatment. We demonstrate by single-cell RNA-Seq analysis that a sub-fraction of surviving BMPR1B+ leukemic stem cells are co-enriched in BMP signaling, quiescence and stem cell signatures, without modulation of the canonical BMP target genes, but enrichment in actors of the Jak2/Stat3 signaling pathway. Indeed, based on a new model of persisting CD34+CD38- leukemic stem cells, we show that BMPR1B+ cells display co-activated Smad1/5/8 and Stat3 pathways. Interestingly, we reveal that only the BMPR1B+ cells adhering to stromal cells display a quiescent status. Surprisingly, this quiescence is induced by treatment, while non-adherent BMPR1B+ cells treated with tyrosine kinase inhibitors continued to proliferate. The subsequent targeting of BMPR1B and Jak2 pathways decreased quiescent leukemic stem cells by promoting their cell cycle re-entry and differentiation. Moreover, while Jak2-inhibitors alone increased BMP4 production by mesenchymal cells, the addition of the newly described BMPR1B inhibitor (E6201) impaired BMP4-mediated production by stromal cells. Altogether, our data demonstrate that targeting both BMPR1B and Jak2/Stat3 efficiently impacts persisting and dormant leukemic stem cells hidden in their bone marrow microenvironment.

Activity of STI571 in chronic myelomonocytic leukemia with a platelet-derived growth factor β receptor fusion oncogene

Blood ◽  
2002 ◽  
Vol 100 (3) ◽  
pp. 1088-1091 ◽  
Author(s):  
Magnus K. Magnusson ◽  
Kristin E. Meade ◽  
Ryotaro Nakamura ◽  
John Barrett ◽  
Cynthia E. Dunbar
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Kinase Inhibitor ◽  
Fusion Gene ◽  
Chronic Myelomonocytic Leukemia ◽  
Platelet Derived Growth Factor ◽  
Gene Transcript ◽  
Molecular Remission ◽  
Β Receptor ◽  
Myelomonocytic Leukemia

Abstract Platelet-derived growth factor β receptor (PDGFβR) fusion genes have been shown to be critical transforming oncogenes in a subset of patients with chronic myelomonocytic leukemia (CMML). The sensitivity of dysregulated tyrosine kinase oncogenes to the tyrosine kinase inhibitor STI571 (imatinib mesylate) makes it a potentially attractive treatment option in this subset of patients. We have recently cloned a novel member of the PDGFβR fusion oncogene family, rabaptin-5-PDGFβR. A patient with CMML carrying the rabaptin-5-PDGFβR fusion gene underwent allogeneic stem cell transplantation (SCT) and was monitored closely with a sensitive reverse transcriptase–polymerase chain assay to detect the novel fusion gene transcript. After achieving a molecular remission at 5 months after transplantation, 15 months after SCT the patient showed persistent and progressive evidence of molecular relapse. After demonstrating in vitro that cells transformed with this specific fusion oncogene are efficiently killed by STI571, the patient was started on STI571. The patient responded rapidly and entered molecular remission after 6 weeks of therapy, and he continues to be in remission 6 months later. These results suggest that STI571 may be an effective targeted therapy in patients with CMML related to PDGFβR fusion oncogenes.

Transforming and Tumorogenic Activity of JAK2 by Fusion to BCR: Molecular Mechanisms of Action of a Novel BCR-JAK2 Tyrosin-Kinase.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4683-4683
Author(s):  
Álvaro Cuesta-Domínguez ◽  
Mara Ortega ◽  
Cristina Ormazabal ◽  
Matilde Santos-Roncero ◽  
Marta Galán-Díez ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Nude Mice ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Lymphoblastic Leukemia ◽  
Chimeric Protein ◽  
Tyrosine Kinase Domain ◽  
Molecular Response

Abstract Abstract 4683 Chromosomal translocations in human tumors frequently produce fusion genes whose chimeric protein products play an essential role in oncogenesis. Recent reports have found a BCR-JAK2 fusion gene in cases of chronic or acute myeloid leukemia, but the protein had not been characterized. We describe a BCR-JAK2 fusion gene by fluorescence in situ hybridization and RT-PCR amplification from bone marrow at diagnosis of a patient with acute lymphoblastic leukemia. After induction therapy, real time PCR showed persistent molecular response correlating with hematological remission maintained up to present. BCR-JAK2 is a 110 KDa chimeric protein containing the BCR oligomerization domain fused to the JAK2 tyrosine-kinase domain. In vitro analysis showed that BCR-JAK2 was constitutively phosphorylated and was located to the cytoplasm. BCR-JAK2 transformed the IL-3-dependent murine hematopoietic cell line Ba/F3 into IL-3 independent growth and induced STAT5b phosphorylation and translocation into the cell nuclei. The treatment with a JAK2 inhibitor abrogated BCR-JAK2 and STAT5b phosphorylation, leading to apoptosis of transformed Ba/F3 cells. To test whether BCR-JAK2 has tumorogenic ability in vivo, we performed experiments with nude mice, in which we injected subcutaneously cells transduced with the control vector and cells expressing BCR-JAK2. Notably, we only obtained tumors in the flank injected with BCR-JAK2 expressing cells, thus confirming the tumorogenic activity of the BCR-JAK2 fusion protein. We conclude that BCR-JAK2 is a new tyrosine-kinase that induces proliferation and cell survival, which can be abrogated by JAK2 inhibitors. In vitro studies demonstrate that BCR-JAK2 displays transforming activity. Moreover, the nude mice model reveals its ability to cause tumors. Disclosures: No relevant conflicts of interest to declare.

The Transcription Factor ELF4 Promotes Survival of Myeloid Leukemic Stem Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1209-1209
Author(s):  
Chun Shik Park ◽  
Koramit Suppipat ◽  
H. Daniel Lacorazza
Keyword(s):  
Stem Cells ◽  
Transcription Factor ◽  
Kinase Inhibitor ◽  
Conflicts Of Interest ◽  
Blast Crisis ◽  
Philadelphia Chromosome ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Leukemic Stem Cells ◽  
Hematopoietic Stem

Abstract Abstract 1209 Chronic myeloid leukemia (CML) is a myeloproliferative disease that originate in hematopoietic stem cells (HSCs) as a result of the t(9;22) translocation, giving rise to the Ph (Philadelphia chromosome) and BCR-ABL oncoprotein. Although treatment of CML patients with tyrosine kinase inhibitor can efficiently eliminate most leukemic cells, chemoresistant leukemic stem cells (LSCs) can survive and drive recurrence of CML in these patients. A number of genes have been described to promote or inhibit proliferation of LSCs. Some of them have similar roles in normal HSCs. The transcription factor ELF4 promotes cell cycle entry of quiescent HSCs during homeostasis (Lacorazza et al., 2006). Thus, to investigate the function of ELF4 in CML initiation and maintenance, we developed a BCR-ABL-induced CML-like disease using retroviral transfer of BCR-ABL in Elf4-null bone marrow (BM) cells. We first investigated whether ELF4 is required for the induction of CML. Recipient mice of BCR-ABL-transduced WT BM cells developed CML and died with a latency 16–23 days, whereas recipient mice of BCR-ABL-transduced Elf4-/- BM cells showed longer latency of 45–47 days (n=20; p<0.0005). Progression of leukemia was monitored in peripheral blood, BM and spleen by flow cytometry. In mice transplanted with BCR-ABL-transduced Elf4-null BM cells, Gr-1+ leukemic cells expanded the first two weeks after BM transplantation followed by a decline at expense of a secondary expansion of B220+ cells. In contrast, Gr-1+ leukemic cells continuously expanded in mice receiving BCR-ABL-transduced WT BM cells. These results suggest that loss of ELF4 causes a profound abrogation in BCR-ABL-induced CML, while allowing progression of B-cell acute lymphocytic leukemia. Since loss of Elf4 led to impaired maintenance of myeloid leukemic cells, we postulated that ELF4 may affect survival of LSCs. Thus, we analyzed the frequency of Lin-c-Kit+Sca-1+ (LSK) cells that are BCR-ABL positive in BM and spleen. We found that BCR-ABL+ LSK cells were significantly reduced in recipients of BCR-ABL-transduced Elf4-/- BM cells. These studies indicate that ELF4 is essential to maintain the LSC pool in CML acting as a molecular switch between myeloid and lymphoid blast crisis. Disclosures: No relevant conflicts of interest to declare.

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