FLT3突变急性髓系白血病的全程管理

约30%的新诊断急性髓系白血病(AML)患者携带FMS样受体酪氨酸激酶3(FLT3)基因突变，大多数FLT3突变是近膜结构域内的内部串联重复(ITD),也有少数是酪氨酸激酶结构域(TKD)内的点突变。FLT3抑制剂的应用改变了FLT3突变AML患者的治疗现状与预后。文章就FLT3突变AML的生物学特征，FLT3突变检测与诊断、FLT3抑制剂的应用及异基因造血干细胞移植中的作用等全程管理进行讨论。     

急性淋巴细胞白血病患者FLT3基因及FLT3/ITD基因突变的检测及临床意义

目的:研究急性淋巴细胞白血病(ALL)患者FLT3基因及其内部串联重复(ITD)突变情况。方法:采用多聚酶链反应(PCR)联合单链构象多态性(SSCP)方法检测76例不同免疫分型ALL患者FLT3基因及FLT3/ITD基因突变。结果:76例ALL患者经PCR扩增发现46例(60.5%)FLT3基因检测阳性,其中前前B细胞ALL、前B细胞ALL、成熟B细胞ALL及T细胞系ALL患者FLT3基因检测阳性率分别为88.2%(15/17),73.9%(17/23),40.0%(6/15)和23.5%(4/17);前前B细胞ALL和前B细胞患者ALL FLT3基因检测阳性率80.0%,显著高于成熟B细胞ALL(40.0%)(P<0.01);B细胞系ALL患者FLT3基因检测阳性率为69.1%,显著高于T细胞系ALL患者(23.5%)(P<0.01)。76例ALL患者中仅有2例(2.6%)出现FLT3/ITD基因突变,此2例均为伴有2种髓系抗原表达,免疫学检查诊断为急性混合细胞白血病患者,均伴有外周血高白细胞数、骨髓中高白血病细胞比例及预后较差。结论:B细胞系ALL和T细胞系ALL患者均可检测出FLT3基因,但B细胞系ALL患者FLT3基因检测阳性率显著高于T细胞系ALL;B细胞系ALL中细胞分化越成熟则FLT3基因检测率阳性越低。ALL患者一般不出现FLT3/ITD基因突变,FLT3/ITD基因突变检测可能有助于急性白血病基因分型及预后判断。     

血液肿瘤患者FLT3/ITD基因突变的检测及临床意义

目的检测血液肿瘤患者FLT3/ITD基因突变,探讨其突变的临床意义。方法2001—2005年对南方医科大学南方医院血液科332例血液肿瘤患者,采用聚合酶链反应(PCR)方法检测FLT3/ITD基因突变。结果FLT3/ITD基因突变阳性率分别为急性髓性白血病(AML)22.3%(23/103)、慢性髓性白血病急变期(CML-BC)6.5%(2/31)、骨髓增生异常综合征(MDS)5.6%(2/36)和急性淋巴细胞白血病(ALL)2.6%(2/76)。而慢性髓性白血病慢性期(CML-CP)、慢性淋巴细胞白血病(CLL)、多发性骨髓瘤(MM)和非霍奇金淋巴瘤(NHL)均未发现FLT3/ITD基因突变。FLT3/ITD基因突变阳性AML患者外周血WBC计数及骨髓白血病细胞比例显著高于FLT3/ITD基因突变阴性AML患者(P<0.05),FLT3/ITD基因突变阳性AML患者完全缓解后18个月内累计复发率(63.6%)显著高于FLT3/ITD基因突变阴性AML组(27.7%)(P<0.05)。结论FLT3/ITD基因突变检测对血液肿瘤预后有一定意义;FLT3/ITD基因突变AML患者预后差。     

PNH患者SCF、FLT3配体及其受体表达的研究

采用酶联免疫吸附法检测阵发性睡眠性血红蛋白尿（PNH）患者的骨髓干细胞生长因子（SCF）和FLT3配体（FL）及其受体含量，用流式细胞术对患者骨髓单个核细胞c kit与FLT3的表达进行分析。结果与对照组比较．PNH患者的SCF无统计学差异（P〉0．05），c kit表达明显降低（P〈0．01），FL含量明显升高（P〈0．01）．FLT3表达与对照组比较P〉0．05。提示SCF、FL及其受体可能参与PNH的发病。     

FLT3突变与白血病预后的研究进展

FLT3又称FLK-2、STK-1,为Ⅲ型受体酪氨酸激酶成员之一,与其配体在正常造血及免疫系统的发育中起重要调节作用.FLT3在急性髓细胞白血病(AML)及急性B淋巴细胞白血病(B-ALL)中有过度表达,其突变是AML中最常见的基因异常.最近研究表明,FLT3过度表达与其突变均可作为预后不良因素,FLT3及其突变可能作为微小残留病灶(MRD)的标志.本文就FLT3及其突变在各型白血病中对预后的意义作一综述.     

阵发性睡眠性血红蛋白尿症与再生障碍性贫血患者干细胞因子和FLT3配体及其受体表达的研究

目的:检测干细胞因子(SCF)与FLT3配体(FL)及其受体在阵发性睡眠性血红蛋白尿(PNH)与再生障碍性贫血(AA)的表达情况,探讨2者在PNH与AA发病中作用。方法:用ELISA法检测PNH与AA患者骨髓SCF和可溶性FL的含量,用流式细胞术对AA与PNH骨髓单个核细胞c kit与FLT3的表达进行分析。结果:PNH、慢性AA患者SCF含量分别为(456.8±115.2)、(372.6±111.5),与正常对照组(389.2±123.3)比较差异无统计学意义(P>0.05);PNH、慢性AA患者c kit表达分别为(48.8±15.6)、(39.6±11.5),低于正常对照组(75.2±23.3)。PNH患者FL水平为226.3±50.6,明显高于正常对照组(89.4±20.8),但低于慢性AA(658.2±125.5)(P<0.01);PNH、慢性AA患者FLT3表达分别为(13.2±5.8)、(8.5±2.7),与正常对照相比差异无统计学意义(P>0.05)。结论:干细胞因子、FLT3配体及其受体参与PNH与AA的发病,2者共同的发病机制可能为干细胞因子受体缺陷、免疫紊乱。     

急性髓系白血病患者miRNA-181b表达特点及预后意义

目的 探讨微小RNA-181b(miR-181b)在急性髓性白血病(AML)中的表达特点及预后意义.方法 采用实时定量逆转录-聚合酶链反应(RT-PCR)检测158例初诊AML患者及20例健康供者骨髓单个核细胞中miR-181b的表达水平.同时采用基因组DNA-PCR结合测序方法检测158例AML患者核磷蛋白1(NPM1)基因第12号外显子突变和fms样酪氨酸激酶3(FLT3)基因内部串联重复(ITD)突变(FLT3-ITD).结果 AML中miR-181b表达水平较正常对照组显著升高(Z =-2.386,P=0.017),各FAB亚型中M1、M5及M6型miR-181b表达水平较对照组明显升高(P＜0.05).miR-181b高表达与低血红蛋白、高乳酸脱氢酶及NPMI野生型有关.miR-181b高表达完全缓解率较低(x2 =7.717,P=0.005)、总生存期较短(P＜0.05).结论 miR-181b在AML某些亚型中高表达,miR-181b高表达是AML患者不利的预后因素.     

骨髓增生异常综合征患者骨髓单个核细胞免疫表型特点及临床意义

目的:探讨骨髓增生异常综合征(MDS)患者骨髓单个核细胞免疫表型特点及临床意义。方法:回顾性分析48例MDS患者免疫表型,对比各亚型间免疫表型表达阳性率的高低,并评估其与IPSS积分的相关性。结果:48例MDS患者骨髓单个核细胞表达CD34、CD117、CD11b、CD33、CD13为主,RAEB1及BAEB2患者CD34、CD117及早期髓系抗原CD33、CD13阳性表达率较RCMD患者增高(P<0.05);骨髓原始细胞比例与CD34、CD117、CD13及CD33阳性表达率呈正相关;对这些患者进行IPSS积分系统评估,高危组CD34及CD117表达阳性率较中危1组升高(P<0.05),CD34表达阳性率与IPSS积分呈正相关。结论:MDS患者进行骨髓单个核细胞免疫表型检测对病情评估及预后判断有重要价值。     

急性髓系白血病的FMS样酪氨酸激酶3的研究和临床意义

FMS样酪氨酸激酶3(FLT3),是Ⅲ型酪氨酸激酶受体(RTKⅢ)的一种,优先表达在定向造血干细胞的细胞表面,与FLT3配体(FL)的相互作用在造血过程的维持,增殖和分化中发挥重要作用。FLT3基因的活性突变是急性髓系白血病(AML)最常见的基因损伤,而且FLT3基因突变通常会给AML患者带来更差的预后。临床上大约30%的AML患者以及少量的急性淋巴细胞白血病(ALL)患者以及骨髓增生异常综合征(MDS)患者发现了FLT3基因的突变。研究FLT3基因突变如何引起基因自身活化和不受机体控制的信号转导的作用机制可能会对突变的FLT3基因如何变成致癌基因…     

FL的生物学作用和临床应用前景

FLT3配体 (FLT3ligand,FL)是一种跨膜蛋白 ,有膜结合型和可溶型两种。虽然在机体中广泛分布 ,但其受体 FLT3却主要表达于早期的造血干细胞。 FL通过与在细胞表面的有酪氨酸激酶活性的受体结合而发挥其造血调节作用。本文对 FL的生物学作用及前景作一综述。l　FL的生物学作用1 .1 　 对造血干、祖细胞的作用FL 主要作用于人 CD34 /CD38-、若丹明1 2 3dull及对 4-氢过氧环磷酰胺有抵抗的造血祖细胞 〔1〕。 FL单用于造血干、祖细胞仅有弱的促增殖作用 ,若与其它细胞因子联用可以促进粒巨噬细胞集落形成单位 (colony- forming unit- …     

Serial determination of FLT3 mutations in myelodysplastic syndrome patients at diagnosis, follow up or acute myeloid leukaemia transformation: incidence and their prognostic significance

The incidence of FLT3 mutations (internal tandem duplication and Asp835) was investigated in bone marrow samples from 97 patients with myelodysplastic syndrome [(MDS); excluding cases with refractory anaemia with excess blasts in transformation] at the time of diagnosis and several time points thereafter. Three patients had FLT3 mutations at presentation. Forty-two patients progressed to acute myeloid leukaemia (AML), including the three patients with FLT3 mutations at MDS diagnosis. Three additional patients acquired FLT3 mutations and progressed to AML in 1 month. FLT3 mutations seem to be a critical additional genetic event that transforms a minority of MDS patients to AML.     

Activating mutation of D835 within the activation loop of FLT3 in human hematologic malignancies

Mutations of receptor tyrosine kinases are implicated in the constitutive activation and development of human malignancy. An internal tandem duplication (ITD) of the juxtamembrane (JM) domain-coding sequence of the FLT3 gene (FLT3/ITD) is found in 20% of patients with acute myeloid leukemia (AML) and is strongly associated with leukocytosis and a poor prognosis. On the other hand, mutations of the c-KIT gene, which have been found in mast cell leukemia and AML, are clustered in 2 distinct regions, the JM domain and D816 within the activation loop. This study was designed to analyze the mutation of D835 of FLT3, which corresponds to D816 of c-KIT, in a large series of human hematologic malignancies. Several kinds of missense mutations were found in 30 of the 429 (7.0%) AML cases, 1 of the 29 (3.4%) myelodysplastic syndrome (MDS) cases, and 1 of the 36 (2.8%) acute lymphocytic leukemia patients. The D835Y mutation was most frequently found (22 of the 32 D835 mutations), followed by the D835V (5), and D835H (1), D835E (1), and D835N (1) mutations. Of note is that D835 mutations occurred independently of FLT3/ITD. An analysis in the 201 patients newly diagnosed with AML (excluding M3) revealed that, in contrast to the FLT3/ITD mutation (n = 46), D835 mutations (n = 8) were not significantly related to the leukocytosis, but tended to worsen disease-free survival. All D835-mutant FLT3 were constitutively tyrosine-phosphorylated and transformed 32D cells, suggesting these mutations were constitutively active. These results demonstrate that the FLT3 gene is the target most frequently mutated to become constitutively active in AML.     

Mutation spectrum of FLT3 and significance of non-canonical FLT3 mutations in haematological malignancy

Fms-like tyrosine kinase 3 (FLT3) is frequently mutated in haematological malignancies. Although canonical FLT3 mutations including internal tandem duplications (ITDs) and tyrosine kinase domains (TKDs) have been extensively studied, little is known about the clinical significance of non-canonical FLT3 mutations. Here, we first profiled the spectrum of FLT3 mutations in 869 consecutively newly diagnosed acute myeloid leukaemia (AML), myelodysplastic syndrome and acute lymphoblastic leukaemia patients. Our results showed four types of non-canonical FLT3 mutations depending on the affected protein structure: namely non-canonical point mutations (NCPMs) (19.2%), deletion (0.7%), frameshift (0.8%) and ITD outside the juxtamembrane domain (JMD) and TKD1 regions (0.5%). Furthermore, we found that the survival of patients with high-frequency (>1%) FLT3-NCPM in AML was comparable to those with canonical TKD. In vitro studies using seven representative FLT3-deletion or frameshift mutant constructs showed that the deletion mutants of TKD1 and the FLT3-ITD mutant of TKD2 had significantly higher kinase activity than wild-type FLT3, whereas the deletion mutants of JMD had phosphorylation levels comparable with wild-type FLT3. All tested deletion mutations and ITD were sensitive to AC220 and sorafenib. Collectively, these data enrich our understanding of FLT3 non-canonical mutations in haematological malignancies. Our results may also facilitate prognostic stratification and targeted therapy of AML with FLT3 non-canonical mutations.     

Incidence and prognosis of c-KIT and FLT3 mutations in core binding factor (CBF) acute myeloid leukaemias

DNA from 110 adult de novo acute myeloid leukaemia (AML) patients exhibiting either inv(16) (n = 63) or t(8;21) (n = 47) was screened for mutations in the c-KIT (exon 8 and Asp816) and FLT3 (ITD and Asp835) genes. c-KIT exon 8 mutations were found in 15/63 (23.8%) inv(16) patients and 1/47 (2.1%) t(8;21) patients. c-KIT Asp816 mutations were present in 5/63 (7.9%) inv(16) AML and 5/47 (10.6%) t(8;21) AML. FLT3 mutations were identified in five patients (7.9%) with inv(16) and three patients (5.6%) with t(8;21) AML. All mutations were mutually exclusive; 40% of inv(16) AML patients possessed either a c-KIT or FLT3 mutation. c-KIT exon 8 mutations were shown to be a significant factor adversely affecting relapse rate.     

NRAS, FLT3 and TP53 mutations in patients with myelodysplastic syndrome and a del(5q)

Mutations of the NRAS and TP53 genes and internal tandem duplication (ITD) of the FLT3 gene are among the most frequently observed molecular abnormalities in the myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). We sought to determine the incidence of these abnormalities in patients with MDS and a 5q deletion. NRAS and FLT3 mutations are uncommon in MDS patients with a 5q deletion and TP53 mutation is associated with the more advanced MDS subtypes.     

Analysis of FLT3 length mutations in 1003 patients with acute myeloid leukemia: correlation to cytogenetics,FAB subtype,and prognosis in the AMLCG study and usefulness as a marker for the detection of minimal residual disease

FLT3 length mutation (FLT3-LM) is a molecular marker potentially useful for the characterization of acute myeloid leukemia (AML). To evaluate the distribution of FLT3-LM within biologic subgroups, we screened 1003 patients with AML at diagnosis for this mutation. FLT3-LM was found in 234 (23.5%) of all patients and thus is the most frequent mutation in AML described so far. Of all positive patients, 165 (70.5%) revealed a normal karyotype. Of the 69 patients with chromosome aberrations, 24 (34.8%) had a t(15;17). The mutation was rare in AML with t(8;21), inv(16) 11q23 rearrangements, and complex karyotypes. FLT3-LM was not distributed equally within different French-American-British (FAB) subtypes and was correlated with a high peripheral blood count in FAB M1, M2, and M4 (P <.0001). In addition, the median age of patients with the mutation was lower (54.9 vs 57.6 years; P =.043), and, at a ratio of 1.36:1 (P =.023), the mutation was more frequent in females than in males. Within the AMLCG study, FLT3-LM was of intermediate prognostic significance. The complete remission rate of 70.3% in patients with FLT3-LM was similar to that (70.4%) in patients without FLT3-LM. Overall survival was not different between patients with or without FLT3-LM. In contrast, patients with FLT3-LM had a significantly shorter event-free survival (7.4 vs 12.6 months; P =.0072) because of a higher relapse rate. Besides the importance of FLT3-LM for biologic and clinical characterization of AML, we show its value as a marker for disease monitoring based on 120 follow-up samples of 34 patients.     

Cloning and expression profile of FLT3 gene during progenitor cell-dependent liver regeneration

BACKGROUND AND AIM: The liver has a unique capacity to regenerate upon exposure to viral infections, toxic reactions and cancer formation. Liver regeneration is a complex phenomenon in which several factors participate during its onset. Cellular proliferation is an important component of this process and the factors that regulate this proliferation have a vital role. FLT3, a well-known hematopoietic stem cell and hepatic lineage surface marker, is involved in proliferative events of hematopoietic stem cells. However, its contribution to liver regeneration is not known. Therefore, the aim of this study was to clone and examine the role of FLT3 during liver regeneration in rats. METHODS: Partial cDNA of rat homolog of FLT3 gene was cloned from thymus and the tissue specific expression of this gene at mRNA and protein levels was examined by RT-PCR and Western blot. After treating with 2-AAF and performing hepatectomy in rats to induce progenitor-dependent liver regeneration, the mRNA and protein expression profile of FLT3 was investigated by real-time PCR and Western blot during liver regeneration. In addition, cellular localization of FLT3 protein was determined by immunohistochemistry. RESULTS: The results indicated that rat FLT3 cDNA has high homology with mouse and human FLT3 cDNA. It was also found that FLT3 is expressed in most of the rat tissues and during liver regeneration. In addition, its intracellular localization is altered during the late stages of liver regeneration. CONCLUSION: The FLT3 receptor is activated at the late stages of liver regeneration and participates in the proliferation response that is observed during progenitor-dependent liver regeneration.