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Schmied BJ, Lutz MS, Riegg F, Zekri L, Heitmann JS, Bühring HJ, Jung G, Salih HR. Induction of NK Cell Reactivity against B-Cell Acute Lymphoblastic Leukemia by an Fc-Optimized FLT3 Antibody. Cancers (Basel) 2019; 11:cancers11121966. [PMID: 31817795 PMCID: PMC6966676 DOI: 10.3390/cancers11121966] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 11/27/2019] [Accepted: 12/04/2019] [Indexed: 01/19/2023] Open
Abstract
Antibody-dependent cellular cytotoxicity (ADCC) is a major mechanism by which antitumor antibodies mediate therapeutic efficacy. At present, we evaluate an Fc-optimized (amino acid substitutions S239D/I332E) FLT3 antibody termed 4G8-SDIEM (FLYSYN) in patients with acute myeloid leukemia (NCT02789254). Here we studied the possibility to induce NK cell ADCC against B-cell acute lymphoblastic leukemia (B-ALL) by Fc-optimized FLT3 antibody treatment. Flow cytometric analysis confirmed that FLT3 is widely expressed on B-ALL cell lines and leukemic cells of B-ALL patients. FLT3 expression did not correlate with that of CD20, which is targeted by Rituximab, a therapeutic monoclonal antibody (mAb) employed in B-ALL treatment regimens. Our FLT3 mAb with enhanced affinity to the Fc receptor CD16a termed 4G8-SDIE potently induced NK cell reactivity against FLT3-transfectants, the B-ALL cell line SEM and primary leukemic cells of adult B-ALL patients in a target-antigen dependent manner as revealed by analyses of NK cell activation and degranulation. This was mirrored by potent 4G8-SDIE mediated NK cell ADCC in experiments with FLT3-transfectants, the cell line SEM and primary cells as target cells. Taken together, the findings presented in this study provide evidence that 4G8-SDIE may be a promising agent for the treatment of B-ALL, particularly in CD20-negative cases.
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Affiliation(s)
- Bastian J. Schmied
- Clinical Collaboration Unit Translational Immunology, German Cancer Consortium (DKTK), Department of Internal Medicine, University Hospital Tübingen, 72076 Tübingen, Germany; (B.J.S.); (M.S.L.); (F.R.); (L.Z.); (J.S.H.)
- DFG Cluster of Excellence 2180 ‘Image-guided and Functional Instructed Tumor Therapy’ (iFIT), Eberhard Karls University, 72076 Tübingen, Germany;
| | - Martina S. Lutz
- Clinical Collaboration Unit Translational Immunology, German Cancer Consortium (DKTK), Department of Internal Medicine, University Hospital Tübingen, 72076 Tübingen, Germany; (B.J.S.); (M.S.L.); (F.R.); (L.Z.); (J.S.H.)
- DFG Cluster of Excellence 2180 ‘Image-guided and Functional Instructed Tumor Therapy’ (iFIT), Eberhard Karls University, 72076 Tübingen, Germany;
| | - Fabian Riegg
- Clinical Collaboration Unit Translational Immunology, German Cancer Consortium (DKTK), Department of Internal Medicine, University Hospital Tübingen, 72076 Tübingen, Germany; (B.J.S.); (M.S.L.); (F.R.); (L.Z.); (J.S.H.)
- DFG Cluster of Excellence 2180 ‘Image-guided and Functional Instructed Tumor Therapy’ (iFIT), Eberhard Karls University, 72076 Tübingen, Germany;
| | - Latifa Zekri
- Clinical Collaboration Unit Translational Immunology, German Cancer Consortium (DKTK), Department of Internal Medicine, University Hospital Tübingen, 72076 Tübingen, Germany; (B.J.S.); (M.S.L.); (F.R.); (L.Z.); (J.S.H.)
- DFG Cluster of Excellence 2180 ‘Image-guided and Functional Instructed Tumor Therapy’ (iFIT), Eberhard Karls University, 72076 Tübingen, Germany;
- Department for Immunology, Eberhard Karls University, 72076 Tübingen, Germany
| | - Jonas S. Heitmann
- Clinical Collaboration Unit Translational Immunology, German Cancer Consortium (DKTK), Department of Internal Medicine, University Hospital Tübingen, 72076 Tübingen, Germany; (B.J.S.); (M.S.L.); (F.R.); (L.Z.); (J.S.H.)
- DFG Cluster of Excellence 2180 ‘Image-guided and Functional Instructed Tumor Therapy’ (iFIT), Eberhard Karls University, 72076 Tübingen, Germany;
| | - Hans-Jörg Bühring
- Department of Hematology and Oncology, Eberhard Karls University, 72076 Tübingen, Germany;
| | - Gundram Jung
- DFG Cluster of Excellence 2180 ‘Image-guided and Functional Instructed Tumor Therapy’ (iFIT), Eberhard Karls University, 72076 Tübingen, Germany;
- Department for Immunology, Eberhard Karls University, 72076 Tübingen, Germany
| | - Helmut R. Salih
- Clinical Collaboration Unit Translational Immunology, German Cancer Consortium (DKTK), Department of Internal Medicine, University Hospital Tübingen, 72076 Tübingen, Germany; (B.J.S.); (M.S.L.); (F.R.); (L.Z.); (J.S.H.)
- DFG Cluster of Excellence 2180 ‘Image-guided and Functional Instructed Tumor Therapy’ (iFIT), Eberhard Karls University, 72076 Tübingen, Germany;
- Correspondence: ; Tel.: +49-7071/29-83275
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Ampasavate C, Jutapakdee W, Phongpradist R, Tima S, Tantiworawit A, Charoenkwan P, Chinwong D, Anuchapreeda S. FLT3, a prognostic biomarker for acute myeloid leukemia (AML): Quantitative monitoring with a simple anti-FLT3 interaction and flow cytometric method. J Clin Lab Anal 2019; 33:e22859. [PMID: 30737839 PMCID: PMC6528579 DOI: 10.1002/jcla.22859] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 01/12/2019] [Accepted: 01/17/2019] [Indexed: 12/18/2022] Open
Abstract
Background Overexpression of fms‐like tyrosine kinase 3 (FLT3) protein in leukemia is highly related to poor prognosis and reduced survival rate in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) patients. Simple but efficient quantification of FLT3 protein levels on the leukemic cell surface using flow cytometry had been developed for rapid determination of FLT3 on intact cell surface. Methods Quantitation protocol for FLT3 biomarker in clinical samples was developed and validated. Cell model selection for calibration curve construction was identified and evaluated. Selected antibody concentrations, cell density, and incubation time were evaluated for most appropriate conditions. Comparison of the developed FLT3 determination protocol with the conventional Western blot analysis was performed. Results EoL‐1 cell line was selected for using as positive control cells. Calibration curve (20%‐120% of FLT3 positive cells) and quality control (QC) levels were constructed and evaluated. The results demonstrated good linearity (r2 > 0.99). The intra‐ and inter‐day precision and accuracy, expressed as the coefficient of variation (%CV) and % recovery, were <20% and fell in 80%‐120% in all cases. When compared with Western blotting results, FLT3 protein expression levels in leukemia patient's bone marrow samples were demonstrated in the same trend. Conclusions The effective, reliable, rapid, and economical analytical technique using the developed flow cytometric method was demonstrated for FLT3 protein determination on leukemic cell surface. This method provided a practical analysis of FLT‐3 biomarker levels which is valuable for physician decision in acute leukemia treatment.
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Affiliation(s)
- Chadarat Ampasavate
- Department of Pharmaceutical Sciences, Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand.,Center for Research and Development of Natural Products for Health, Chiang Mai University, Chiang Mai, Thailand
| | - Wasimon Jutapakdee
- Department of Pharmaceutical Sciences, Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand
| | - Rungsinee Phongpradist
- Department of Pharmaceutical Sciences, Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand
| | - Singkome Tima
- Division of Clinical Microscopy, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand
| | - Adisak Tantiworawit
- Division of Hematology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Pimlak Charoenkwan
- Department of Pediatrics, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
| | - Dujrudee Chinwong
- Department of Pharmaceutical Care, Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand
| | - Songyot Anuchapreeda
- Center for Research and Development of Natural Products for Health, Chiang Mai University, Chiang Mai, Thailand.,Division of Clinical Microscopy, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand
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FLT3 receptor/CD135 expression by flow cytometry in acute myeloid leukemia: Relation to FLT3 gene mutations and mRNA transcripts. EGYPTIAN JOURNAL OF MEDICAL HUMAN GENETICS 2018. [DOI: 10.1016/j.ejmhg.2018.04.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Impact of FLT3 Receptor (CD135) Detection by Flow Cytometry on Clinical Outcome of Adult Acute Myeloid Leukemia Patients. CLINICAL LYMPHOMA MYELOMA & LEUKEMIA 2018; 18:541-547. [PMID: 29907544 DOI: 10.1016/j.clml.2018.05.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 05/04/2018] [Accepted: 05/17/2018] [Indexed: 12/18/2022]
Abstract
BACKGROUND The significance of FMS-like tyrosine kinase 3 (FLT3)-ITD mutation in acute myeloid leukemia (AML) prognosis has been well established. The aims of this study were to investigate the prognostic impact of the FLT3 protein (CD135) expression and its association with FLT3-ITD mutation, and to identify its role in minimal residual disease. PATIENTS AND METHODS CD135 was measured by flow cytometry on leukemic blasts of 257 adults with de novo AML. High expression of CD135 ≥ 20% was correlated with clinical, laboratory, and other prognostic factors that influenced treatment outcome. FLT3-ITD mutation was tested by PCR. RESULTS The frequency of CD135 expression was 138 (53.7%) of 257. FLT3-ITD was detected in (21.4%). Positive CD135 expression was associated with high total leukocyte count (P = .006), platelet count (P = .003), monocytic leukemia (P < .001), and CD34 (P = .008) and CD117 (P = .006) expression. CD135 expression ≥ 25% was a predictor of FLT3-ITD mutation (P = .03). CD135 overexpression was a negative predictor of complete remission and of postinduction minimal residual disease at days 14 and 28 (P < .001). CD135 had an adverse impact on overall and disease-free survival (68.5% vs. 15%, P = .002). Multivariate analysis indicated CD135 was the sole independent prognostic factor for overall survival (hazard ratio = 2.49; 95% confidence interval, 1.855-3.345; P < .001). CONCLUSION CD135 is emerging as a prognostic factor, a new marker for minimal residual disease, and a potential novel therapeutic target of AML.
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CAR T-cells targeting FLT3 have potent activity against FLT3 -ITD + AML and act synergistically with the FLT3-inhibitor crenolanib. Leukemia 2018; 32:1168-1179. [PMID: 29472720 DOI: 10.1038/s41375-018-0009-0] [Citation(s) in RCA: 125] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 12/05/2017] [Accepted: 12/07/2017] [Indexed: 12/26/2022]
Abstract
FMS-like tyrosine kinase 3 (FLT3) is a transmembrane protein expressed on normal hematopoietic stem and progenitor cells (HSC) and retained on malignant blasts in acute myeloid leukemia (AML). We engineered CD8+ and CD4+ T-cells expressing a FLT3-specific chimeric antigen receptor (CAR) and demonstrate they confer potent reactivity against AML cell lines and primary AML blasts that express either wild-type FLT3 or FLT3 with internal tandem duplication (FLT3-ITD). We also show that treatment with the FLT3-inhibitor crenolanib leads to increased surface expression of FLT3 specifically on FLT3-ITD+ AML cells and consecutively, enhanced recognition by FLT3-CAR T-cells in vitro and in vivo. As anticipated, we found that FLT3-CAR T-cells recognize normal HSCs in vitro and in vivo, and disrupt normal hematopoiesis in colony-formation assays, suggesting that adoptive therapy with FLT3-CAR T-cells will require subsequent CAR T-cell depletion and allogeneic HSC transplantation to reconstitute the hematopoietic system. Collectively, our data establish FLT3 as a novel CAR target in AML with particular relevance in high-risk FLT3-ITD+ AML. Further, our data provide the first proof-of-concept that CAR T-cell immunotherapy and small molecule inhibition can be used synergistically, as exemplified by our data showing superior antileukemia efficacy of FLT3-CAR T-cells in combination with crenolanib.
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Tarlock K, Alonzo TA, Loken MR, Gerbing RB, Ries RE, Aplenc R, Sung L, Raimondi SC, Hirsch BA, Kahwash SB, McKenney A, Kolb EA, Gamis AS, Meshinchi S. Disease Characteristics and Prognostic Implications of Cell-Surface FLT3 Receptor (CD135) Expression in Pediatric Acute Myeloid Leukemia: A Report from the Children's Oncology Group. Clin Cancer Res 2017; 23:3649-3656. [PMID: 28108543 DOI: 10.1158/1078-0432.ccr-16-2353] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 12/20/2016] [Accepted: 01/05/2017] [Indexed: 01/24/2023]
Abstract
Purpose: The FLT3 cell-surface receptor tyrosine kinase (CD135) is expressed in a majority of both acute lymphoid leukemia (ALL) and myeloid leukemia (AML). However, the prognostic significance of CD135 expression in AML remains unclear. We therefore evaluated the association between FLT3 surface expression and disease characteristics and outcomes in pediatric patients with AML.Experimental Design: We analyzed FLT3 receptor expression on AML blasts by multi-dimensional flow cytometry and its association with disease characteristics, clinical outcomes, and FLT3 transcript level in 367 children with AML treated on the Children's Oncology Group trial AAML0531.Results: There was high variability in blast CD135 cell-surface expression across specimens. CD135 expression measured by flow cytometry was not correlated with FLT3 transcript expression determined by quantitative RT-PCR. Overall, CD135 expression was not significantly different for patients with FLT3/WT, FLT3/ITD, or FLT3/ALM (P = 0.25). High cell-surface CD135 expression was associated with FAB M5 subtype (P < 0.001), KMT2A rearrangements (P = 0.009), and inversely associated with inv(16)/t(16;16) (P < 0.001). Complete remission rate, overall survival, disease-free survival, and relapse rates were not significantly different between patients with low and high CD135 expression.Conclusions: FLT3 cell-surface expression did not vary by FLT3 mutational status, but high FLT3 expression was strongly associated with KMT2A rearrangements. Our study found that there was no prognostic significance of FLT3 cell surface expression in pediatric AML. Clin Cancer Res; 23(14); 3649-56. ©2017 AACR.
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Affiliation(s)
- Katherine Tarlock
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington. .,Department of Pediatrics, Seattle Children's Hospital, University of Washington, Seattle, Washington
| | - Todd A Alonzo
- Children's Oncology Group, Monrovia, California.,Keck School of Medicine, University of Southern California, Los Angeles, California
| | | | | | - Rhonda E Ries
- Department of Pediatrics, Seattle Children's Hospital, University of Washington, Seattle, Washington
| | - Richard Aplenc
- Division of Hematology/Oncology, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania
| | - Lillian Sung
- Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, Ontario
| | | | - Betsy A Hirsch
- Division of Laboratory Medicine, University of Minnesota Medical School, Minneapolis, Minnesota
| | | | | | - E Anders Kolb
- Nemours/Alfred I. duPont Hospital for Children, Wilmington, Delaware
| | - Alan S Gamis
- Children's Mercy Hospitals and Clinics, Kansas City, Missouri
| | - Soheil Meshinchi
- Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington.,Department of Pediatrics, Seattle Children's Hospital, University of Washington, Seattle, Washington
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Abd El-Ghaffar AA, El-Gamal RA, Mostafa NN, Abou Shady NM. FLT3 (CD135) and Interleukin-2 receptor alpha-chain (CD25) expression in acute myeloid leukemia: improving the correspondence to FLT3 - internal tandem duplication mutation. Int J Lab Hematol 2016; 38:e69-72. [DOI: 10.1111/ijlh.12493] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - R. A. El-Gamal
- Department of Clinical Pathology; Ain Shams University Hospitals; Cairo Egypt
| | - N. N. Mostafa
- Clinical Hematology and Bone Marrow Transplantation Unit; Department of Internal Medicine; Cairo Egypt
| | - N. M. Abou Shady
- Department of Pediatrics; Ain Shams University Hospitals; Cairo Egypt
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Kim M, Kim J, Kim JR, Han E, Park J, Lim J, Kim Y, Han K, Kim HJ, Min WS, Cho B. FLT3 expression and IL10 promoter polymorphism in acute myeloid leukemia with RUNX1-RUNX1T1. Mol Biol Rep 2014; 42:451-6. [PMID: 25287662 DOI: 10.1007/s11033-014-3786-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 09/30/2014] [Indexed: 10/24/2022]
Abstract
We investigated the correlation between FLT3 expression and IL10 gene promoter polymorphism in acute myeloid leukemia with RUNX1-RUNX1T1 and their clinical significance. FLT3 mRNA expression was measured by real-time quantitative PCR (qPCR) and immunohistochemical staining (IHC) on bone marrow (BM) leukemic cells. IL10 gene promoter polymorphisms including rs1800896 (G-1082A), rs1800871 (C-819T), and rs1800872 (C-592T) were genotyped by direct sequencing. Among 45 enrolled patients, 32 (71.1 %) exhibited FLT3 overexpression, whose FLT3 mRNA level was higher than normal cut-off value (0.02). The IHC results also consisted with FLT3 mRNA expression data achieved by qPCR. The FLT3 mRNA level was significantly different among 3 IHC staining groups (P < 0.0001); 0.031 ± 0.041, 0.106 ± 0.097 and 0.588 ± 0.573 in IHC negative, intermediate and positive group, respectively. Interestingly, the FLT3 expression level was correlated with the percentage of BM CD34 positive cells (R = 0.360, P = 0.016). The elevated FLT3 expression at initial BM were decreased after remission and maintained lower than the cut-off level. FLT3 expression was not dependent on IL10 gene promoter polymorphisms. FLT3 overexpression itself did not demonstrate significant effects on overall survival (OS). However, it is notable that IL10 rs1800896 GA genotype tended to have a lower estimated mean OS (20.1 months) compared to GG genotype (54.6 months), but the statistical significance was not derived because of limited number of patients in this study (P = 0.072). Further studies including more type of leukemia and patients may be helpful to understand the relations between cytokine genotype and FLT3 expression and their prognostic impact.
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Affiliation(s)
- Myungshin Kim
- Department of Laboratory Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul, 137-701, Korea
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Sharawat SK, Bakhshi R, Vishnubhatla S, Gupta R, Bakhshi S. FLT3-ITD mutation in relation to FLT3 expression in pediatric AML: a prospective study from India. Pediatr Hematol Oncol 2014; 31:131-7. [PMID: 24498869 DOI: 10.3109/08880018.2013.870624] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
There is lack of data with regard to FLT3 expression in FLT3-ITD positive pediatric AML patients. Further, FLT3-ITD has not been systematically analyzed for outcome from Indian subcontinent. Amongst 64 consecutive pediatric AML patients, FLT3-ITD was present in 12 (19%) patients. All patients with FLT3-ITD achieved CR; those with FLT3-ITD mutation had inferior DFS (P = .029). FLT3 expression by flow-cytometry was observed in all FLT3-ITD positive patients, whereas 40/52 (77%) FLT3-ITD negative patients expressed FLT3 (P = .06). FLT3 expression in 12 FLT3-ITD positive patients was unable to show an association between FLT3 expression and outcome. In FLT3-ITD negative patients, higher surface expression of FLT3 significantly predicted poor EFS (P = .001) and OS (P = .007).
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Affiliation(s)
- Surender Kumar Sharawat
- Department of Medical Oncology, Dr. B. R.A. Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India
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Weisberg E, Ray A, Nelson E, Adamia S, Barrett R, Sattler M, Zhang C, Daley JF, Frank D, Fox E, Griffin JD. Reversible resistance induced by FLT3 inhibition: a novel resistance mechanism in mutant FLT3-expressing cells. PLoS One 2011; 6:e25351. [PMID: 21980431 PMCID: PMC3182213 DOI: 10.1371/journal.pone.0025351] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 09/01/2011] [Indexed: 12/12/2022] Open
Abstract
Objectives Clinical responses achieved with FLT3 kinase inhibitors in acute myeloid leukemia (AML) are typically transient and partial. Thus, there is a need for identification of molecular mechanisms of clinical resistance to these drugs. In response, we characterized MOLM13 AML cell lines made resistant to two structurally-independent FLT3 inhibitors. Methods MOLM13 cells were made drug resistant via prolonged exposure to midostaurin and HG-7-85-01, respectively. Cell proliferation was determined by Trypan blue exclusion. Protein expression was assessed by immunoblotting, immunoprecipitation, and flow cytometry. Cycloheximide was used to determine protein half-life. RT-PCR was performed to determine FLT3 mRNA levels, and FISH analysis was performed to determine FLT3 gene expression. Results and Conclusions We found that MOLM13 cells readily developed cross-resistance when exposed to either midostaurin or HG-7-85-01. Resistance in both lines was associated with dramatically elevated levels of cell surface FLT3 and elevated levels of phosphor-MAPK, but not phospho-STAT5. The increase in FLT3-ITD expression was at least in part due to reduced turnover of the receptor, with prolonged half-life. Importantly, the drug-resistant phenotype could be rapidly reversed upon withdrawal of either inhibitor. Consistent with this phenotype, no significant evidence of FLT3 gene amplification, kinase domain mutations, or elevated levels of mRNA was observed, suggesting that protein turnover may be part of an auto-regulatory pathway initiated by FLT3 kinase activity. Interestingly, FLT3 inhibitor resistance also correlated with resistance to cytosine arabinoside. Over-expression of FLT3 protein in response to kinase inhibitors may be part of a novel mechanism that could contribute to clinical resistance.
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MESH Headings
- Cell Line, Tumor
- Cell Proliferation/drug effects
- Drug Resistance, Neoplasm/drug effects
- Drug Resistance, Neoplasm/genetics
- Enzyme Stability/drug effects
- Enzyme Stability/genetics
- Gene Expression Regulation, Neoplastic/drug effects
- Gene Expression Regulation, Neoplastic/genetics
- Half-Life
- Humans
- Leukemia, Myeloid, Acute/genetics
- Leukemia, Myeloid, Acute/metabolism
- Leukemia, Myeloid, Acute/pathology
- Mutation
- Phosphorylation/drug effects
- Phosphorylation/genetics
- Piperazines/pharmacology
- Protein Kinase Inhibitors/pharmacology
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Signal Transduction/drug effects
- Signal Transduction/genetics
- Staurosporine/analogs & derivatives
- Staurosporine/pharmacology
- Thiazoles/pharmacology
- Tyrosine/metabolism
- Up-Regulation/drug effects
- fms-Like Tyrosine Kinase 3/antagonists & inhibitors
- fms-Like Tyrosine Kinase 3/chemistry
- fms-Like Tyrosine Kinase 3/genetics
- fms-Like Tyrosine Kinase 3/metabolism
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Affiliation(s)
- Ellen Weisberg
- Department of Medical Oncology/Hematologic Neoplasia, Dana Farber Cancer Institute, Boston, Massachusetts, United States of America.
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