实时定量RT-PCR检测慢性粒细胞白血病bcr/abl融合基因的临床意义

目的：建立实时定量RT-PCR方法检测慢性粒细胞白血病(CML)bcr／abl mRNA的方法；探讨CML bcr／abl融合基因的表达水平与疗效的关系。方法：可同时检测b2a2和b3a2两种亚型．GAPDH的mRNA作为内参照。检测14例CML患者的22个外周血和骨髓样本中bcr／abl融合基因表达水平．并对2例异基因造血干细胞移植后复发的患者进行动态监测。结果：bcr／abl及GAPDH标准曲线的相关系数均为0．999；灵敏度为10^-6；14例初诊患者的mRNA表达水平范围为2．81～145；2例异基因造血干细胞移植后复发患者的bcr／abl mRNA表达水平随临床治疗而变化。结论：实时定量PCR检测CML患者的bcr／abl融合基因，敏感可靠，重复性好；其融合基因表达水平的改变与临床疾病进展关系相一致，有助于反映白血病细胞负荷、评价疗效及判断疾病预后。     

Blast crisis in a murine model of chronic myelogenous leukemia.

The P210bcr/abl protein is produced in cells from patients with Philadelphia chromosome-positive chronic myelogenous leukemia (CML). Retroviral transfer of the gene encoding P210bcr/abl into murine bone marrow induces a granulocytic leukemia that models the chronic phase of human CML. We have transferred the leukemic clone to syngeneic animals, albeit with surprising inefficiency, and have observed CML and clonally related acute leukemias of lymphoid or myeloid phenotype in some transplant recipients. These data show that murine CML can result from retroviral transfer of the bcr/abl gene into pluripotent hematopoietic stem cells, that infected clones repopulate poorly after adoptive transfer, and that these clones can give rise to acute leukemia, reflecting evolution to a phase resembling blast crisis in the human disease.     

Alpha-interferon reduces in vivo phosphorylation of P210bcr/abl protein during hemin-induced erythroid differentiation of K-562 cells

alpha-Interferon (IFN-alpha) is important in the management of chronic myelogenous leukemia (CML). The P210bcr/abl fusion protein, with enhanced tyrosine kinase activity, is implicated in the pathogenesis and progression of the disease. To elucidate the inhibitory mechanism of IFN-alpha on CML cell proliferation, we studied the effect of IFN-alpha on P210bcr/abl in K-562 cells. The phosphorylated level of P210bcr/abl was not altered by treatment with IFN-alpha alone despite its inhibiting cell proliferation. However, when K-562 cells were treated with either a low (5 x 10(2) U/ml) or high (10(4) U/ml) concentration of IFN-alpha in the presence of hemin, P210bcr/abl protein activity decreased through reduction of in vivo phosphorylation, but not through inhibition of de novo protein synthesis. Furthermore, hemoglobin content was increased by IFN-alpha at both low and high concentrations in tandem with hemin-induced erythroid differentiation and the change in P210bcr/abl. These results demonstrate that IFN-alpha synergises hemin-mediated erythroid differentiation as it reduces the in vivo tyrosine phosphorylation of P210bcr/abl in K-562 cells.     

A possible correlation between the type of bcr-abl hybrid messenger RNA and platelet count in Philadelphia-positive chronic myelogenous leukemia.

The Philadelphia (Ph1) chromosome, in which the hybrid bcr-abl gene is formed, is thought to be the initial event in chronic myelogenous leukemia (CML). The position of the breakpoint within the breakpoint cluster region (bcr) on Ph1 chromosome and the splicing pattern determine the species of the fused bcr-abl messenger RNA (mRNA). We tried to detect the two types of fused mRNAs in 57 chronic-phase cases of Ph1-positive CML using the polymerase chain reaction procedure (RT-PCR). The bcr exon 2/abl exon 2 fused mRNA (b2-a2) was detected in 17 patients, the bcr exon 3/abl exon 2 fused mRNA (b3-a2) was detected in 34 patients, and both types of mRNA were detected in six patients. The platelet counts of patients who expressed b3-a2 mRNA or both types were significantly higher than those of patients who expressed only b2-a2 (841.5 v 373.5 x 10(9)/L; P less than .015), although there was no significant difference in the white blood cell counts or hemoglobin. This finding suggests a possibility that the type of bcr-abl mRNA may affect the thrombopoietic activity in CML.     

造血干细胞移植后白血病细胞染色体核型和bcr/abl融合基因表达观察

目的：探讨造血干细胞移植(HSCT)后白血病细胞染色体核型和基因表达观察的意义。方法：用骨髓细胞短期培养法和直接法G显带分析染色体；双色荧光原位杂交检测bcr／abl融合基因。结果：2例供者为女性的男性急性髓细胞白血病(AML)患者异体外周血干细胞移植(allo-PBSCT)后染色体检测持续46，XX。最长生存50个月。4例慢性髓细胞白血病(CML)经allo-PBSCT后，Ph染色体和bcr／abl融合基因阳性1例，经供者淋巴细胞输注加干扰素治疗，已生存70个月。Ph染色体阴性bcr／abl融合基因阳性2例，最长生存27个月。Ph染色体阳性bcr／abl融合基因阴性1例，已生存14个月。2例AML自体造血干细胞移植后检测出非特征性染色体畸变，复发后再化疗达完全缓解，最长生存期达81个月。结论：造血干细胞移植后白血病细胞遗传学检测可观察近期疗效，指导后续治疗选择。     

应用RT-nest-PCR法检测慢性髓细胞白血病非亲缘异基因骨髓移植后微小残留病变

目的：应用筑巢式RT—PCR（RT—nest-PCR）法检测慢性髓细胞性白血病（CML）患者非亲缘异基因骨髓移植（URD）后微小残留病变（MRD），并探讨它与复发的相关性。方法：分别采用RT-nest—PCR法和常规细胞遗传学方法检测bcr／abl融合基因和Ph染色体。结果：20例CML行URD患者术前Ph染色体和bcr／abl融合基因检测均为阳性，移植术后30dPh染色体皆转为阴性，bcr／abl融合基因完全转阴时间为1～3个月，中位时间2个月；在随防的18例CML患者中，有16例患者bcr／abl融合基因完全转阴后没再转为阳性。在1例复发的CML患者中可见到血型、Ph染色体和bcr／abl融合基因动态变化，另1例CML患者在移植成功后的21个月和36个月检测到bcr／abl融合基因，经随访未见临床和血液学复发征象。结论：检测bcr／abl融合基因是目前观察CML患者非亲缘异基因骨髓移植后微小残留病变最敏感的方法之一，非亲缘异基因骨髓移植能最大限度地消除CML患者体内残留病变，患者能长期无病生存。     

CML patients in blast crisis have breakpoints localized to a specific region of the BCR

Chronic myelogenous leukemia (CML) is associated with the Philadelphia (Ph) chromosome, which results from a reciprocal translocation between chromosomes 9 and 22. This activates the abl oncogene by moving it from chromosome 9 and combining it with sequence located on chromosome 22. The new fusion gene, with chromosome 22 sequence at its 5' end and chromosome 9-abl sequence at its 3' end, generates a new messenger RNA (mRNA) and protein that are implicated in the pathogenesis of CML. The breakpoint near the c-abl locus on chromosome 9 can occur within a large area. In contrast, the breakpoints on chromosome 22 are concentrated within a 6 kilobase (kb) region termed the breakpoint cluster region (bcr). This study was designed to determine whether chronic-phase and blast crisis patients had identifiable differences in the structure of their Ph chromosomes. Restriction mapping of the chromosome 22 translocation breakpoints performed for 26 patients showed that the breakpoints of eight of the nine patients in blast crisis were in the 3' portion of the bcr, whereas the breakpoints in the 17 patients in the chronic phase were clustered in the 5' portion of the bcr. This suggests a strong correlation between a 3' bcr breakpoint and blast crisis in CML.     

Mutations of the ras protooncogenes in chronic myelogenous leukemia: a high frequency of ras mutations in bcr/abl rearrangement-negative chronic myelogenous leukemia

Seventy cases of chronic myelogenous leukemia (CML) were analyzed for the presence of ras mutations using polymerase chain reaction (PCR), oligonucleotide hybridization, and direct PCR sequencing. All cases had preceding cytogenetic and bcr rearrangement studies. Aberrant ras genes were detected in none of 39 patients with Philadelphia (Ph) chromosome or bcr/abl rearrangement positive chronic-phase CML and in only 1 of 18 patients in blast crisis, suggesting that ras mutations have little or no role in initiation or progression of common CML. Seven of 13, or 54% of patients with bcr/abl rearrangement negative chronic phase CML (atypical CML) harbored mutations in ras, however. This high incidence of ras mutations, together with the absence of bcr/abl rearrangement, provides evidence that atypical CML is an entity that is molecularly distinct from common CML. Moreover, the clinical characteristics and the high frequency of ras mutations suggest that atypical CML may constitute a subset of the myelodysplastic syndrome and may be best classified as a variant of chronic myelomonocytic leukemia (CMML).     

Immunologic characterization of the tumor-specific bcr-abl junction in Philadelphia chromosome-positive acute lymphoblastic leukemia

Philadelphia (Ph')-positive acute lymphoblastic leukemia (ALL) is highly associated with two forms of chimeric bcr-abl proteins: P190bcr-abl and P210bcr-abl. Whereas P210bcr-abl also occurs in chronic myeloid leukemia, P190bcr-abl is uniquely expressed in Ph'-positive ALL. As a consequence, P190bcr-abl is preeminently a tumor-specific marker in leukemic cells of ALL patients. Because P190bcr-abl is composed of the normal bcr and abl proteins, the major part of the P190bcr-abl molecule comprises nontumor-specific determinants. The joining region between bcr and abl, newly generated during the Ph' translocation, is exclusively a tumor-specific epitope on the P190bcr-abl molecule. Therefore, only antibodies against the bcr-abl joining region will detect the tumor-specificity of P190bcr-abl. In this study a polyclonal antiserum, termed BP-ALL, was raised against a synthetic peptide corresponding to the bcr-abl junction in P190bcr-abl. The reactivity of BP-ALL with native P190bcr-abl derived from a Ph'-positive ALL cell line (TOM-1) was tested using immunoprecipitation analysis. BP-ALL reacted highly specifically with P190bcr-abl but not with P210bcr-abl isolated from chronic myeloid leukemia cell lines. Peptide inhibition studies further confirmed the fine specificity of BP-ALL. Our data indicate that the tumor-specific bcr-abl junction domain is exposed in an antigenic fashion on the P190bcr-abl molecule.     

Two bcr/abl fusion gene products, P210bcr/abl and P190bcr/abl, are equally sensitive to the protein tyrosine phosphatase of mature granulocytes.

Two bcr/abl fusion gene products with tyrosine kinase activity have been found in two phenotypes of Philadelphia chromosome (Ph1)-positive leukemia. P210bcr/abl (P210) is associated with Ph1-positive chronic myelogenous leukemia (CML), while P190bcr/abl is associated with Ph1-positive acute leukemia. We compared the susceptibility of 32Pi-labeled P210 from K-562 cells and P190 from MR-87 cells to protein tyrosine phosphatase (PTPase). PTPase, present in the lysate of mature granulocytes from CML patients as well as in the lysate of these cells from normal subjects, effectively dephosphorylated the CML-associated P210 and the acute leukemia associated P190. This PTPase activity was specifically inhibited by ZnCl2; it was not present in lymphocyte lysates, and was not inhibited by neutralization with anti-CD45 antibody. Since P210 and P190 were equally sensitive to the PTPase, the difference in leukemic phenotypes associated with the expression of these two tyrosine kinases cannot be explained by the differential dephosphorylation of P210 and P190.     

巢式聚合酶链反应检测慢性粒细胞白血病bcr／abl融合基因

目的 探讨Ph染色体和bcr/abl融合基因在慢性粒细胞白血病（CGL）的发病机制、诊断、治疗、预后判断的价值。方法 对46例CGL患者作巢式逆转录聚合酶链反应（RT-PCR）检测bcr/abl融合基因,同时对其中28例作细胞遗传学检查。结果 46例CGL患者中,44例bcr/abl融合基因阳性,阳性率为95.7%;28例CGL患者作细胞遗传学检查。26例Ph染色体阳性,阳性率为92.9%;2例Ph染色体阴性的CGL患者,用RT-PCR检测出ber/abl融合基因。结论 巢式RT-PCR是一种快速、敏感而准确的检测方法,可以为部分Ph染色体阴性的CGL患者提供分子生物学的诊断依据。     

T cell recognition of bcr/abl in healthy donors and in patients with chronic myeloid leukaemia

In chronic myeloid leukaemia (CML), peptides from the fusion region of bcr3/abl2 are likely to play a role in anti-leukaemic T cell immunity. We investigated whether T cells that recognize bcr/abl fusion peptides could be detected in healthy donors and CML patients. T cell responses against bcr3/abl2 fusion peptides were analysed by gamma-interferon enzyme-linked immunospot assays after prestimulation of peripheral blood mononuclear cells in the presence of anti-CD3-antibodies and interleukin-2. Our results suggest that the T cell repertoire contains bcr3/abl2-reactive T cells in CML patients who are in cytogenetic remission, but also in some healthy individuals.     

Molecular remission of CML after autotransplantation followed by adoptive transfer of costimulated autologous T cells

Four patients with chronic myelogenous leukemia (CML) that was refractory to interferon alpha (two patients) or imatinib mesylate (two patients), and who lacked donors for allogeneic stem cell transplantation, received autotransplants followed by infusions of ex vivo costimulated autologous T cells. At day +30 (about 14 days after T-cell infusion), the mean CD4+ cell count was 481 cells/microl (range 270-834) and the mean CD8+ count was 516 cells/microl (range 173-1261). One patient had a relative lymphocytosis at 3.5 months after T-cell infusion, with CD4 and CD8 levels of 750 and 1985 cells/microl, respectively. All the four patients had complete cytogenetic remissions early after transplantation, three of whom also became PCR negative for the bcr/abl fusion mRNA. One patient, who had experienced progressive CML while on interferon alpha therapy, became PCR- post transplant, and remained in a molecular CR at 3.0 years of follow-up. All the four patients survived at 6, 9, 40, and 44 months post transplant; the patient who remained PCR+ had a cytogenetic and hematologic relapse of CML, but entered a molecular remission on imatinib. Autotransplantation followed by costimulated autologous T cells is feasible for patients with chronic phase CML, who lack allogeneic donors and can be associated with molecular remissions.     

Clonal evolution in a myeloid cell line transformed to interleukin-3 independent growth by retroviral transduction and expression of p210bcr/abl.

Current evidence suggests that the expression of the tyrosine kinase p210bcr/abl in chronic myelogenous leukemia (CML) may directly induce the initial phase of granulocytic hyperplasia. However, the dysregulation of additional genes appears to be required for transition to the acute leukemic phase, as inferred by the appearance of recurrent secondary cytogenetic abnormalities in the majority of patients. To determine whether the expression of p210bcr/abl alone is responsible for this genetic instability, we introduced and expressed the bcr/abl gene from a retroviral vector in a clone of the interleukin-3 (IL-3) dependent myeloblastic 32D C13(G) cell line. Clonal and polyclonal cells transformed to IL-3 independent growth were observed for a period extending up to 6 months for changes in the expression of p210bcr/abl, cell proliferation, inhibition by prostaglandin E1 (PGE1), forskolin, and cyclic adenosine monophosphate (cAMP) analogues, regulation of the cell cycle, and karyotype. Whereas the properties of control vector infected 32D C13(G)' cells remained stable over time, cells expressing p210bcr/abl were phenotypically unstable. In cells expressing p210bcr/abl, we observed selective modulation of p210bcr/abl mRNA and protein expression, evolution from partial to full abrogation of IL-3 dependence, reduced serum requirements, increased cell proliferation, decreased inhibition by PGE1 and cAMP analogues, and the appearance of new structural and numerical chromosomal abnormalities with successive cell passages. These results indicate that expression of p210bcr/abl can directly predispose 32D C13(G)' cells to genetic instability, promotes the emergence of clones with an increased proliferative advantage, and may represent an in vitro model suitable for the study of mechanisms underlying progression to the acute leukemic phase in CML.     

The coiled-coil domain and Tyr177 of bcr are required to induce a murine chronic myelogenous leukemia-like disease by bcr/abl

The bcr/abl fusion in chronic myelogenous leukemia (CML) creates a chimeric tyrosine kinase with dramatically different properties than intact c-abl. In P210 bcr/abl, the bcr portion includes a coiled-coil oligomerization domain (amino acids 1-63) and a grb2-binding site at tyrosine 177 (Tyr177) that are critical for fibroblast transformation, but give variable results in other cell lines. To investigate the role of the coiled-coil domain and Tyr177 in promoting CML, 4 P210 bcr/abl-derived mutants containing different bcr domains fused to abl were constructed. All 4 mutants, Delta(1-63) bcr/abl, (1-63) bcr/abl, Tyr177Phe bcr/abl, and (1-210) bcr/abl exhibited elevated tyrosine kinase activity and conferred factor-independent growth in cell lines. In contrast, differences in the transforming potential of the 4 mutants occurred in our mouse model, in which all mice receiving P210 bcr/abl-expressing bone marrow cells exclusively develop a myeloproliferative disease (MPD) resembling human CML. Of the 4 mutants assayed, only 1-210 bcr/abl, containing both the coiled-coil domain and Tyr177, induced MPD. Unlike full-length P210, this mutant also caused a simultaneous B-cell acute lymphocytic leukemia (ALL). The other 3 mutants, (1-63) bcr/abl, Tyr177Phe bcr/abl, and Delta(1-63) bcr/abl, failed to induce an MPD but instead caused T-cell ALL. These results show that both the bcr coiled-coil domain and Tyr177 are required for MPD induction by bcr/abl and provide the basis for investigating downstream signaling pathways that lead to CML.