Humans ; Leukemia, Myeloid, Acute ; drug therapy ; Molecular Targeted Therapy ; fms-Like Tyrosine Kinase 3 ; metabolism

Nucleophosmin (NPM) is a protein that shuttles between the nucleus, nucleoplasm and cytoplasm. NPM gene mutations and aberrant cytoplasmic NPM localization have been recently described in acute myelogenous leukemia (AML) with normal karyotype and in a few myelodysplastic syndromes. Expression of NPM mutant reduces the ability of Arf to initiate a p53 response and to induce cell cycle arrest. Clinical research has revealed that NPM mutations are relative to prognosis and can be used to monitor and quantify minimal residual disease (MRD) in AML patients with normal karyotype, therefore, these findings indicate that nucleophosmin mutations might contribute to illustration of myeloid leukemogenesis. In this paper, the research progress of nucleophosmin mutations in haematological malignancies was reviewed.
Cell Nucleolus ; metabolism ; Hematologic Neoplasms ; genetics ; pathology ; Humans ; Mutation ; Nuclear Proteins ; genetics ; fms-Like Tyrosine Kinase 3 ; genetics

Receptor tyrosine kinases couple a wide variety of extracellular cues to cellular responses. The class III subfamily comprises the platelet-derived growth factor receptor, c-Kit, Flt3 and c-Fms, all of which relay cell proliferation signals upon ligand binding. Accordingly, mutations in these proteins that confer ligand-independent activation are found in a subset of cancers. These mutations cluster in the juxtamembrane (JM) and catalytic tyrosine kinase domain (TKD) regions. In the case of acute myeloid leukemia (AML), the juxtamembrane (named ITD for internal tandem duplication) and TKD Flt3 mutants differ in their spectra of clinical outcomes. Although the mechanism of aberrant activation has been largely elucidated by biochemical and structural analyses of mutant kinases, the differences in disease presentation cannot be attributed to a change in substrate specificity or signaling strength of the catalytic domain. This review discusses the latest literature and presents a working model of differential Flt3 signaling based on mis-localized juxtamembrane autophosphorylation, to account for the disease variation. This will have bearing on therapeutic approaches in a complex disease such as AML, for which no efficacious drug yet exists.
Cell Membrane ; metabolism ; Humans ; Leukemia, Myeloid, Acute ; enzymology ; genetics ; metabolism ; Models, Biological ; Mutation ; Protein Structure, Tertiary ; Signal Transduction ; fms-Like Tyrosine Kinase 3 ; chemistry ; genetics ; metabolism

FMS-like tyrosine kinase 3 (FLT3) is a receptor of tyrosine kinase that is constitutively activated in most of acute myeloid leukemia patients and seems to give an adverse prognosis. In order to explore the silencing effect of FLT3 targeted short hairpin RNA (FLT3-shRNA) on acute leukaemia cell line THP-1, three FLT3-shRNAs (shRNA1, shRNA2, shRNA3) were designed and synthesized by transcription system in vitro and then transfected into THP-1 cells. FLT3 mRNA was analyzed by semi-quantitative RT-PCR, FLT3 protein was detected by Flow cytometry and immunofluorescence. The results indicated that FLT3 expression was downregulated by shRNA1 and shRNA3, and shRNA1 showed stronger inhibitory effect. At 48 hours following transfection, the inhibitory rate of 25 nmol/L shRNA1 was 72.95 +/- 2.07%, lasting 72 hours. The 5 nmol/L and more concentration of FLT3 shRNA1 could downregulate FLT3 mRNA level, which displayed a quantity-effect relation; the inhibitory rate of 15 nmol/L shRNA1 was 67.53 +/- 0.66%. FLT3 protein was located on THP-1 cell membrance, its expression was downregulated obviously by shRNA1, at 72 hours following transfection the inhibitory rate of shRNA1 was 79.67 +/- 0.66%. shRNA1 showed the best inhibitory effect on FLT3 protein, the optimal time of which was 72 hours with an inhibitory rate of 79.67%. It is concluded that FLT3-shRNA1 shows a desireable FLT3-targeted inhibitory effect, which can be used for further investigation of FLT3 mechanism or FLT3 targeting treatment.
Humans ; Leukemia, Myeloid, Acute ; genetics ; metabolism ; RNA Interference ; RNA, Messenger ; genetics ; RNA, Small Interfering ; genetics ; Transcription, Genetic ; Tumor Cells, Cultured ; fms-Like Tyrosine Kinase 3 ; genetics

OBJECTIVEFMS-like tyrosine kinase 3 (FLT3) is a receptor tyrosine kinase that is constitutively activated in (70-90)% pediatric patients with acute myeloid leukemia (AML) and appears to confer an adverse prognosis. Although several FLT3-selective small molecule inhibitors and antibodies were developed with varied degrees of success, to address the specificity and resistance, new approaches for specifically targeted FLT3 are needed and RNA interference is a promising choice. The aim of the present study was to investigate the efficacy of suppression of FLT3 induced by small hairpin interfering RNA (shRNA) on myeloproliferation and apoptosis in an acute monocytic leukemia (AMOL) cell line THP-1.

METHODSFLT3-targeted small hairpin interfering RNA (FLT3-shRNA) was designed and synthesized by transcription system in vitro was transfected into THP-1 cells. Firstly FLT3 mRNA level was detected by semi-quantitative RT-PCR and FLT3 protein level was detected by flow cytometry (FCM) to verify the efficacy on FLT3-shRNA interference at 48 h after transfection. Cell growth viability was measured at 24 h, 48 h and 72 h after treatment with CCK-8. The distribution of cell cycle was assayed by FCM, and apoptosis was analyzed by DNA Ladder and Annexin V-FITC Staining at 48 h.

RESULTSFLT3 targeted shRNAs was synthesized successfully and the concentration of 15 nmol/L for 48 h could obtain desirable downregulation of FLT3 expression, the inhibitory percentages of FLT3 mRNA and protein were (72.95 +/- 2.07)% and (65.39 +/- 5.57)%, respectively. The suppression of FLT3 induced by FLT3-shRNA resulted in marked inhibition of cell growth and the inhibitory percentages were (36.66 +/- 3.67)% at 48 h, (35.56 +/- 0.73)% at 72 h. FLT3-shRNA induced the inhibition of cell cycle from G(0)/G(1) phase to S phase, the percentage of sub-G(0)/G(1) phase (65.71 +/- 4.47)% was higher than those in the PBS-control group (52.23 +/- 2.98)%, NC-shRNA control group (51.81 +/- 1.44)%, P < 0.01; the percentage of S phase (25.11 +/- 2.70)% was lower than those in the PBS-control group (34.41 +/- 4.07)% and NC-shRNA control group (32.50 +/- 1.46)%, P < 0.05. Furthermore treatment with FLT3-shRNA for 48 h resulted in clear apoptosis ladder, the percentage of early apoptosis detected by Annexin V-FITC was (18.59 +/- 2.07)% which was significantly higher than that in the PBS-control group (4.00 +/- 0.50)% and the NC-shRNA control group (6.06 +/- 0.70)%, P < 0.001.

CONCLUSIONThe suppression of FLT3 induced by the shRNA can effectively inhibit cell proliferation, and apoptosis induction on THP-1 cells, which indicates that this approach may bear the therapeutic potential on childhood AMOL.

Apoptosis ; drug effects ; genetics ; Cell Proliferation ; drug effects ; Child ; Humans ; Leukemia, Monocytic, Acute ; enzymology ; pathology ; Protein-Tyrosine Kinases ; metabolism ; RNA Interference ; physiology ; RNA, Small Interfering ; pharmacology ; Receptor Protein-Tyrosine Kinases ; metabolism ; fms-Like Tyrosine Kinase 3 ; metabolism

No abstract available.
Adolescent ; Child ; Flow Cytometry ; Gene Rearrangement ; Humans ; Immunophenotyping ; Karyotyping ; Male ; Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/*diagnosis ; Receptors, Antigen, T-Cell/genetics/metabolism ; fms-Like Tyrosine Kinase 3/genetics

Minimal residual disease (MRD) is an important cause of relapse and disease-free survival time decrease in patients with acute myeloid leukemia (AML). This study was aimed to explore the role of FLT3 gene in AML pathogenesis and its significanse for detection of MRD. Using genomic PCR, 125 AML patients were detected for FLT3 gene expression before and after chemical therapy and allogeneic hematopoietic stem cell transplantation (allo-HSCT), meantime the AML patients with FLT3 positive expression were observed by follow-up. The results showed that the sensitivity of PCR was 10(-4) in FLT3 gene detection; the rates of FLT3 positive expression were 69.6% and 44.90% in the newly diagnosed AML patients and complete remission (CR) patients respectively. The rate of FLT3 expression coverted to negative was 48.98% in treated AML patients, while no change of FLT 3 expression was found in 6.12% treated patients. The FLT3 expression converted to positive in relapsed patients, and FLT3 expression remains positive in non-remitted patients. The CR rate in FLT3 positive expression patients before treatment was significantly lower than that in FLT3 negative expression patients, the difference of which was statistically significant (p < 0.05). The AML relapse rate in FLT3 positive patients was significantly higher than that in FLT3 negative expression patients (p < 0.05). It is concluded that FLT3 gene expression is related to leukemia pathogenesis; the dynamic levels of FLT3 expression before and after treatment can be used for estimating prognosis of AML patients and detecting MRD.
Adolescent ; Adult ; Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Biomarkers, Tumor ; Bone Marrow Transplantation ; Child ; Child, Preschool ; Female ; Humans ; Infant ; Leukemia, Myeloid, Acute ; genetics ; therapy ; Male ; Middle Aged ; Neoplasm, Residual ; Young Adult ; fms-Like Tyrosine Kinase 3 ; metabolism

OBJECTIVETo study the efficacy and safety of sorafenib combined with low dose cytarabine for treating patients with FLT3(+) relapsed and refractory acute myeloid leukemia (FLT3(+) RR-AML).

METHODSSeven patients with FLT3(+) RR-AML were treated with sorafenib and low dose cytarabine. The curative rate and adverse effects were observed in these patients.

RESULTSOut of 7 RR-AML patients after treatment, 5 patients achieved complete remission (CR), 2 patients achieved partial remission (PR), and the overall response rate (ORR) after one course of therapy was 100%. No severe bleeding, nausea, vomiting and other side effects were found in these patients.

CONCLUSIONSorafenib combined with low dose cytarabine can effectively induce the remission of FLT3(+) RR-AML patients, and is worth for further clinical trails to verify its safty and efficiency.

Cytarabine ; therapeutic use ; Humans ; Leukemia, Myeloid, Acute ; drug therapy ; Niacinamide ; analogs & derivatives ; therapeutic use ; Phenylurea Compounds ; therapeutic use ; Recurrence ; Remission Induction ; Treatment Outcome ; fms-Like Tyrosine Kinase 3 ; metabolism

This study was aimed to explore the relationship between Flt-3 expression, Flt-3/ITD mutation in acute leukemia (AL) cell line and pathogenesis of AL, especially AML. The Flt-3 expression and Flt-3/ITD mutation were detected by RT-PCR and sequencing method in 82 leukemia cell lines including 20 AML, 57 ALL and 5 CML cell lines. The results indicated that positive results of Flt-3 expression were obtained in 48 out of 77 AL cell line, the positive rate was 62%; 12 cell lines were positive in 20 AML cell lines, the positive rate was 60%; 33 cell lines was positive in 57 ALL cell lines, the positive rate was 58%; 3 cell lines were positive in 5 CML cell lines, the positive rate was 60%. There was abnormal gene product in 1 AMOL cell line out of 12 AML cell lines with Flt-3 positive expression (positive rate 8.3%). DNA sequencing of abnormal gene product showed two coding duplication sequence with 29 bp long. The positive rate of Flt-3 expression in undifferentiated cell line was prominently higher than that in mature B cell ALL (P < 0.05). It is concluded that the Flt-3 expression is different in various leukemia cells. Flt-3/ITD duplication was found in one AML cell line. The detection of Flt-3 gene and Flt-3/ITD mutation may contribute to the diagnosis of ALL, especially to AML.
Base Sequence ; Gene Duplication ; Gene Expression Regulation, Neoplastic ; Humans ; Leukemia, Myeloid, Acute ; genetics ; metabolism ; Molecular Sequence Data ; Mutation ; Tandem Repeat Sequences ; Tumor Cells, Cultured ; fms-Like Tyrosine Kinase 3 ; biosynthesis ; genetics

Objective of this study was to detect the expression of Survivin in acute myeloid leukemia (AML) and investigate the relationship of its expression levels with clinical variates and its correlations with BCL-2 ,Bcl-xL and MCL-1. The expression of Survivin, BCL-2, Bcl-xL and MCL-1 were measured by immunohistochemistry in bone marrow biopsy of 63 newly diagnosed AML patients, and the relationship between its expression level and clinical parameters (age, sex, WBC count, diagnosis, prognosis), especially fusion protein AML1/ETO was investigated. The results showed that the expression level of Survivin in newly diagnosed AML patients was higher than that of normal controls (P < 0.01), the expression levels of Survivin did not correlate with age, sex, and WBC counts of patients and so on. There was no significant difference of Survivin expression between different NCCN prognosis groups, either between patients with AML1/ETO or FLT3-ITD mutation and the other patients. Survivin positive patients were got to have lower CR rate but higher relapse rate, however that was not significant in statistics. Indeed, the cumulative survivin rate of Survivin positive patients were lower than that of Survivin negative patients (P = 0.04). Finally, positive correlation between Survivin and MCL-1 was also observed (r = 0.639, P = 0.000). It is concluded that overexpression of Survivin are closely related with occurrence and development of acute leukemia, and may be used as an indicator of prognosis evaluation. In addition, Survivin and MCL-1 may have a relationship of cooperation or interaction.
Adolescent ; Adult ; Core Binding Factor Alpha 2 Subunit ; metabolism ; Female ; Humans ; Inhibitor of Apoptosis Proteins ; metabolism ; Leukemia, Myeloid, Acute ; metabolism ; pathology ; Male ; Middle Aged ; Mutation ; Myeloid Cell Leukemia Sequence 1 Protein ; metabolism ; Oncogene Proteins, Fusion ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; RUNX1 Translocation Partner 1 Protein ; Young Adult ; bcl-X Protein ; metabolism ; fms-Like Tyrosine Kinase 3 ; metabolism