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At least 973 records · Page 54Linked to original sources
PubMed2003

[The effect of anti-bcr-abl hammerhead ribozyme on bone marrow purging].

To study effects of a hammerhead ribozyme on chronic myelogenous leukemia (CML) cells and bone marrow purging in vitro, a bcr-abl specific ribozyme gene was introduced into CML and normal bone marrow cells using retroviral transduction. The effects of the ribozyme on primary cells from CML patients were detected by hematopoietic progenitor cell assays, flow cytometry and immunocytochemical methods. Then a model of remission was built up, and the effects of ribozyme on bone marrow purging were detected by leukemia colony assay and nest-PCR after transduction of this model by using the ribozyme. The results showed that ribozyme significantly suppressed the clonogenic growth and the expression of p210 protein in primary cells from CML patients, but did not affect the growth of normal hematopoietic progenitor cells. In the model of remission, ribozyme eliminated the proliferation and the expression of bcr-abl mRNA in residual K562 cells, but did not affect the expression of abl mRNA. The results suggest that anti-bcr-abl ribozyme might be used for bone marrow puring of CML cells.

Bone Marrow Cells↗
PubMed1992

Amplification and sequencing of genomic breakpoints located within the M-bcr region by Vectorette-mediated polymerase chain reaction.

The polymerase chain reaction (PCR) cannot be used to amplify the breakpoint in the chimaeric BCR-ABL gene in CML and acute leukaemias due to the large variation in the sites of breakpoint in the BCR gene (within a 5.8 kb region) and in the ABL gene (within a 150 kb region). The disease state is usually monitored using RNA-PCR to monitor abnormal transcripts. We have used a new modification of the PCR to amplify breakpoints within zone 3 of the M-bcr. A synthetic oligonucleotide linker, the Vectorette, is ligated to restriction digested DNA, and amplification is carried out between primers for a known target sequence and the Vectorette linker. Three Philadelphia chromosome Ph1-positive CML patients with breakpoints within the ALU region of zone 3 have been amplified and the sequence immediately around the breakpoint determined. The breaks occurred within 70 bp and two were only 14 bp apart. The Vectorette-PCR technique has the potential to rapidly identify and sequence breakpoints, and will enable the design of patient-specific primers to monitor disease progression, particularly following bone marrow transplantation.

Base Sequence↗
PubMed2003

Bcr-Abl kinase modulates the translation regulators ribosomal protein S6 and 4E-BP1 in chronic myelogenous leukemia cells via the mammalian target of rapamycin.

Identification of signaling pathways downstream of Abl tyrosine kinase may increase our understanding of the pathogenesis of chronic myelogenous leukemia (CML) and suggest strategies to improve clinical treatment of the disease. By combining the use of a phosphospecific antibody recognizing a substrate motif of serine/threonine kinases with bioinformatics, we found that the translational regulators ribosomal protein S6 and 4E-BP1 are constitutively phosphorylated in CML cells. Experiments with specific inhibitors indicated the phosphorylation is downstream of Bcr-Abl kinase and the mammalian target of rapamycin (mTOR). These results suggest that Bcr-Abl may regulate translation of critical targets in CML cells via mTOR. They also provide a rationale for testing the combination of mTOR inhibitors with the Abl kinase inhibitor imatinib in patients with CML. The mTOR inhibitor rapamycin enhanced imatinib-mediated killing of CML cell lines in vitro, and it overcame imatinib resistance in cells with Bcr-Abl gene amplification.

Adaptor Proteins, Signal Transducing↗
PubMed1992

[i(17q) appearing in acute phase in Ph1-negative, BCR-negative CML].

A 36-year-old woman was referred to our hospital because of splenomegaly in February 1989. The leukocyte count was 55,500/microliter without hiatus leukemicus. The leukocyte alkaline phosphatase score was low (29). The bone marrow showed myeloid hyperplasia (24.8% myeloblasts) but no dysplastic change. The karyotype of the bone marrow cells was 46, XX and a diagnosis of Ph1 (-) CML was made. Treatment with VCR, 6MP and prednisolone made 7-month duration chronic phase, but the abnormal karyotype.[46, XX, i(17q)] gradually increased to 100% of bone marrow cells. The patient died in June 1990. The evidence that not only a BCR rearrangement but also messages of BCR/ABL fusion gene were negative made us able to differentiate this case from Ph1(-), BCR(+) CML. The addition of an i(17q) results in partial monosomy of 17q (17q13;p53 gene) and partial trisomy of 17q (17q11.2-12;G-CSF gene). We examined the rearrangement of p53 gene and G-CSF-dependent tumor cell growth in vitro, demonstrating one allelic loss of p53 gene and independent cell growth on G-CSF respectively. It is thought that in Ph1 (-), BCR (-) CML as well as in Ph1 (+) CML, an i(17q) is related to the progression but not to the initiation of these leukemias. However the precise mechanism, including p53 gene inactivation by point mutation, is still to be elucidated.

Adult↗
PubMed2006

Quantitative real-time RT-PCR monitoring of BCR-ABL in chronic myelogenous leukemia shows lack of agreement in blood and bone marrow samples.

Molecular monitoring of the BCR-ABL transcript in chronic myelogenous leukemia (CML) using quantitative RT-PCR provides clinicians with important diagnostic and prognostic information. To determine whether molecular detection and monitoring of CML is comparable using peripheral blood (PB) and bone marrow (BM) aspirate samples, we performed a prospective study using quantitative real-time RT-PCR (QRT-PCR) of paired PB and BM samples from 41 patients with CML entered onto a single Cancer and Leukemia Group B (CALGB) treatment study. QRT-PCR analysis of PB and BM samples was performed prior to initiation of, and during, treatment with homoharringtonine and cytarabine on a CALGB study for previously untreated CML. Statistical analyses demonstrated good agreement of PB and BM pre-treatment samples. However, using the Bland-Altman statistical method that measures true agreement between PB and BM values, we found that there was only modest agreement of BCR-ABL measurements in PB and BM for samples obtained during treatment. PB values obtained during treatment tended to be lower than the corresponding BM values [average difference = -0.37 (p<0.001) in 36 paired samples] and the 95% limits of agreement ranged from -1.23 to 0.48. Nevertheless, our study demonstrates that BM and PB QRT-PCR values followed a similar trend during treatment (Spearman correlation coefficient, 0.83; 95% CI, 0.70, 0.96). Our data suggest that, quantitatively, PB and BM measurements of BCR-ABL are frequently disparate. Since BM values tended to be higher than PB values, BM sampling provides the most accurate assessment of minimal residual disease (MRD). Based on these results, we caution against interchanging BM with PB sampling for MRD monitoring during treatment of CML since this may lead to misinterpretation of treatment results.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

[Atypical chronic myeloid leukemia with polymorphism of the BCR gene].

The region of greatest rupture of the gene BCR (M-bcr) was analysed with the restriction enzyme Bgl II plus a molecular probe containing the 5' end of M-bcr in a woman with atypical, Ph'-negative chronic myelogenous leukaemia. An abnormal DNA fragment of 5.0 kb and an extra band were found, suggesting rearrangement. Nevertheless, the use of several restriction enzymes and the addition of a different probe showed the existence of polymorphism with the enzyme Bgl II, which is an unusual finding. These findings stress the usefulness of using different restriction enzymes and molecular probes in the molecular study of chronic myelogenous leukaemia.

Female↗
PubMed1988

Absence of alternative splicing in bcr-abl mRNA in chronic myeloid leukemia cell lines.

The major consequence of the Philadelphia (Ph) translocation in chronic myeloid leukemia (CML) is the formation of a bcr-abl hybrid oncogene encoding a tumor cell-specific protein P210bcr-abl. In contrast to this, in Ph chromosome-positive acute lymphoblastic leukemia (Ph + ALL), a P190bcr-abl can be observed. This P190bcr-abl has been implicated in acute rather than chronic leukemogenesis. Therefore, it can be hypothesized that the transition from chronic to blast phase in CML is accompanied by an alternative splice in the bcr-abl mRNA, which results in a switch of the production of P210bcr-abl into P190bcr-abl. Initial S1 nuclease protection mapping supported this theory. However, this result appears to be based on an artifact in the S1 analysis. By using the polymerase chain reaction we provide evidence for the absence of alternative splicing in bcr-abl mRNA in two CML blast crisis cell lines.

Blast Crisis↗
PubMed1995

Late appearance of a Philadelphia translocation with minor-BCR/ABL transcript in a t(7;11)(p15;p15) acute myeloid leukemia.

We describe a patient with a t(7;11)(p15;p15) acute myeloid leukemia who was subsequently found to harbor the Philadelphia (Ph) translocation, in addition to the t(7;11), at the second relapse. A BCR/ABL transcript was detected at the second relapse by reverse transcription-polymerase chain reaction assay; the leukemic cells had a BCR/ABL fusion gene involving the minor breakpoint cluster region (minor-BCR; situated in intron 1 of the BCR gene). Although the Ph translocation is commonly detected in de novo acute leukemia and chronic myeloid leukemia as the primary leukemia-specific chromosomal translocation, our case suggests that this cytogenetic change might occur as an additional chromosomal change in neoplastic cells. Moreover, minor-BCR/ABL rearrangements may also occur as a late appearance of Ph translocation.

Base Sequence↗
PubMed1995

Are ABL and BCR imprinted? No definitive answers, but more questions.

The apparent nonrandom contribution of the paternally-derived chromosome 9 and the maternally-derived chromosome 22 to the leukemia-specific translocation t(9;22)(q34;q11) obtained by cytogenetic analysis suggested that the two genes affected by this rearrangement, namely ABL and BCR, are imprinted. The results of recent molecular genetic studies have challenged this notion, since it was shown that both the paternal as well as the maternal BCR- and ABL-alleles may be affected by the translocation event and that both genes may be expressed from both alleles. This paper offers possible explanations for the apparent contradictory results obtained through cytogenetic and molecular genetic means. Based on the few available data concerning their allelic methylation pattern, replication behavior and expression status, as well as by referring to similar problems encountered in other genes whose imprinting status had also remained elusive for a long time, I argue that it still remains likely that ABL and BCR are imprinted.

Alleles↗
PubMed1995

Standpoint on imprinting of BCR and ABL.

Cytogenetic studies of Ph-positive leukemic patients and their parents have indicated that chromosome 22 involved in the formation of the t(9;22) is of maternal origin, whereas chromosome 9 is preferentially of paternal origin. These data have suggested that the two genes BCR and ABL, which become fused through the translocation, might be imprinted, ie expressed in a parental-specific manner. Recent molecular genetic studies however, have shown that BCR and ABL are expressed on both alleles and that the maternal and paternal ABL genes contribute equally often to the BCR-ABL fusion messenger. The findings make imprinting of these genes unlikely as an explanatory model and necessitate a combined cytogenetic and molecular genetic study.

Alleles↗
PubMed1995

Polymerase chain reaction detection of the BCR-ABL fusion transcript after allogeneic marrow transplantation for chronic myeloid leukemia: results and implications in 346 patients.

We studied 346 patients after bone marrow transplantation (BMT) for chronic myeloid leukemia (CML) for the presence of the bcr-abl transcript detected by the polymerase chain reaction (PCR) to understand the frequency and implication of a positive test. A total of 634 samples of BM and/or peripheral blood were obtained for PCR analysis between 3 and 192 months after BMT. A positive PCR test at 3 months post-BMT was not statistically significantly associated with an increased risk of relapse compared with PCR-negative patients. However, a positive PCR assay at 6 months and beyond was highly associated with subsequent relapse. The Kaplan-Meier estimate of relapse for patients testing PCR-positive at 6 to 12 months was 42% versus 3% for PCR-negative patients (P < .0001). The Kaplan-Meier estimate of survival at 4 years for the PCR-positive patients was 74% compared with 83% for the PCR-negative group (P = .002). Multivariable analysis indicated that a PCR-positive result at 6 to 12 months post-BMT, the type of BMT donor (allogeneic matched donor v mismatched or unrelated), and the presence of acute GVHD were independent risk factors for subsequent relapse. The relative risk (RR) for relapse for patients PCR-positive at 6 to 12 months post-BMT was 26.1 (95% confidence interval, 8.9 to 76.1, P < .0001). The outcome of long-term patients (> 36 months post-BMT) who tested PCR-positive was much better, as 15 of 59 (25%) tested positive for bcr-abl, but only one patient relapsed. There was a 91% concordance between PCR tests of simultaneously obtained BM and peripheral blood. These analyses show that the PCR assay of the bcr-abl fusion transcript 6 to 12 months post-BMT is an independent predictor of subsequent relapse which provides an opportunity for early therapeutic intervention.

Adolescent↗
PubMed1995

Detection of BCR-ABL transcripts from the Philadelphia translocation by hybridization in microtiter wells and time-resolved immunofluorometry.

Two hybridization assays have been developed to detect BCR-ABL mRNA transcripts arising from the Philadelphia translocation. Both assays use time-resolved immunofluorometric detection of polymerase chain reaction-amplified BCR-ABL mRNA sequences hybridized to specific probes. In configuration I, biotinylated amplified target is immobilized onto streptavidin-coated wells and hybridized to a probe labeled with the hapten digoxigenin. Hybrids are detected via an alkaline phosphatase-labeled antibody and fluorosalicylylphosphate as substrate. The fluorosalicylate produced forms highly fluorescent complexes with Tb(3+)-EDTA. In configuration II, biotinylated probe is immobilized onto streptavidin-coated wells. PCR, performed in the presence of hapten-labeled deoxyribonucleotide, generates labeled product, which is hybridized to immobilized probe and quantified as above. BCR-ABL transcripts from one leukemic cell amidst mRNA from 500,000 normal granulocytes are detectable with signal/background ratios as high as 36.4 and 24.6 for configurations I and II, respectively. The respective CVs for the assays were 6.6-9.0% and 5.1-12.5%.

Base Sequence↗
PubMed1994

A novel transcriptional suppressor located within a downstream intron of the BCR gene.

A reciprocal translocation between chromosomes 9 and 22 creates the Philadelphia (Ph1) chromosome in chronic myelogenous leukemia. This translocation results in the fusion of the ABL and the BCR genes to form a BCR/ABL fusion gene, the product of which has a greatly increased protein tyrosine kinase activity in comparison with the normal ABL protein. The chromosome 22 translocation breakpoints are concentrated within a 5.8-kilobase region named the major break-point cluster region (Mbcr). Gel mobility shift and DNase I footprinting assays have defined binding sites for three proteins, BIF 1-3 (BCR intron factors 1-3), lying within a 427-base pair fragment of the Mbcr. This 427-base pair fragment functions as a transcriptional silencer with both the BCR as well as a heterologous promoter. The silencing is position- and orientation-independent. The transcriptional effects are greatest in chronic myelogenous leukemia cells, decreased in HeLa and B-cells, and absent in T-lymphocytes. Gel mobility shift assays show a corresponding difference in pattern when the T-lymphocyte nuclear extract is compared with other cell lines. The Mbcr appears to contain a novel group of transcriptional silencers that share a common binding motif with a recently described suppressor in the mouse Adh-1 gene.

Base Composition↗
PubMed1993

DNA sequence analysis of the major breakpoint cluster region of the BCR gene rearranged in Philadelphia-positive human leukemias.

We sought sequence characteristics that might explain the apparent high recombination frequency of the 5-kb BglII segment containing M-bcr exons 1, 2 and 3, and the intron to exon 4. An Alu sequence (subfamily Sx), in 5'-->3' orientation, lay in the middle of a 3-kb region that contains the great majority of Philadelphia chromosome breakpoint sites. The breakpoint of only one out of five chronic myeloid leukemia patients, for whom the BCR breakpoint site had been sequenced, was located within this Alu. Other features of interest for recombination were a 51-bp AT-rich region close to the 3' end, six hypervariable minisatellite consensus octamers, GC[A/T]GG[A/T]GG, six lymphoid recombinase heptamer signal sequences, one nonamer and a 16-bp inverted repeat. Dot matrix comparisons of the 5-kb M-bcr sequence with a 3-kb m-bcr2 segment showed significant homology only in corresponding Alu sequences.

Base Sequence↗
PubMed1995

5-Fluorouracil-resistant CD34+ cell population from peripheral blood of CML patients contains BCR-ABL-negative progenitor cells.

Despite the marked expansion of leukemic cells observed in the hematopoietic system of chronic myeloid leukemia (CML) patients, there is clinical and experimental evidence that normal nonclonal cells persist in the bone marrow (BM) and peripheral blood (PB) of patients in the early chronic phase. In this study, we attempt to select the benign progenitor-enriched population from the PB of CML patients. The CD34+ cells isolated from the PB of 12 CML patients in the chronic phase were treated with low doses (5 or 10 micrograms/mL) of 5-fluorouracil (5-FU). We expanded these cells for 7 days in liquid cytokine-mediated cultures. This expansion in the presence of interleukin-1 (IL-1) plus stem cell factor (SCF) plus IL-3 or leukemia inhibitory factor (LIF) plus SCF plus IL-3 seemed at least to preserve the initial clonogenic potential of CD34+ and 5-FU-resistant CD34+ cells. For the presence of BCR-ABL, mRNA from each of the 12 patients was studied by reverse-transcriptase-polymerase chain reaction (RT-PCR) on 10-15 pooled CFU-GM colonies plucked from methylcellulose cultures of starting and expanded populations. Although all PCR results were positive for colonies harvested before liquid culture, we were able to identify BCR-ABL-negative colonies from an expanded CD34+ population cultured in the presence of recombinant cytokines in 11 of 12 patients studied. 5-FU pretreatment of CML CD34+ cells markedly reduced their clonogenic potential and growth factor-mediated cell proliferation but favored higher frequency of BCR-ABL-free colonies. In conclusion, these data show that 5-FU-resistant CD34+ cells from the PB of CML patients contain normal progenitor cells, which can be selected and expanded in short-term cytokine-mediated cultures.

Antigens, CD34↗
PubMed1997

Improved sensitivity of BCR-ABL detection: a triple-probe three-color fluorescence in situ hybridization system.

Chronic myeloid leukemia is a clonal stem cell disorder associated with the Philadelphia (Ph) translocation [t(9;22) (q34;q11)]. As a result of the Ph translocation, parts of the ABL and BCR genes become fused. Cytogenetic quantification of Ph+ metaphases can be used to monitor patient response to treatment but is of limited sensitivity and applies only to cycling cells. Fluorescence in situ hybridization (FISH) with probes from the BCR and ABL regions can also identify the Ph translocation in interphase cells. Established systems for the detection of fusion genes by FISH rely on colocalization of two different probes but are associated with a high rate of false-positive results. We have introduced a third probe labeled with a different fluorochrome to create a triple-probe/three-color system that permits identification of both the Ph chromosome and the derivative 9 chromosome in Ph+ cells. This system was used to determine the frequency of interphase cells carrying the BCR-ABL fusion gene in bone marrow and peripheral blood granulocytes from patients showing variable cytogenetic responses to interferon. Our data show that the triple-probe/three-color approach allows highly sensitive detection of residual disease. Moreover, this method is readily applicable to the analysis of other chromosome translocations.

Adult↗
PubMed1997

Location of the BCR-ABL fusion gene on the 9q34 band in two cases of Ph-positive chronic myeloid leukemia.

Two new variant Philadelphia (Ph) chromosomes with an aberrant location of the BCR-ABL fusion gene on 9q34 of the derivative 9 are reported. One presented cytogenetically as a standard t(9;22)(q34;q11), whereas the other was classified as an ins(9;22)(q34;q11.1q11.2) using the combined interpretation of cytogenic, FISH, and molecular data. The mechanisms of the two rearrangements are presented. It is suggested that the insertion has occurred in a single event in the patient with ins(9;22). In the patient with t(9;22), both a translocation and an insertion, occurring either sequentially or simultaneously, can account for the location of the BCR-ABL fusion gene on the derivative 9. A possible poor prognostic impact of this aberrant location of the BCR-ABL is also suggested by the clinical data reported in such patients.

Aged↗
PubMed1993

rho family GTPase activating proteins p190, bcr and rhoGAP show distinct specificities in vitro and in vivo.

rho family GTPases link extracellular signals to changes in the organization of cytoskeletal actin. Serum stimulation of quiescent Swiss 3T3 fibroblasts leads to rho-dependent actin stress fibre formation and focal adhesions, whilst several growth factors initiate signalling pathways leading to rac-dependent actin polymerization at the plasma membrane, and membrane ruffling. The product of the breakpoint cluster region gene bcr, rho GTPase accelerating protein (rhoGAP) and rasGAP-associated p190 share structurally related rho GAP domains, and possess GAP activity for rho family members in vitro. We have directly compared the activities of the isolated GAP domains of these three proteins in regulating different rho family GTPases, both by in vitro assays and by microinjection, to address their possible physiologic functions. We show that bcr accelerates the GTPase activity of rac, but not rho in vitro, and inhibits rac-mediated membrane ruffling, but not rho-mediated stress fibre formation, after microinjection into Swiss 3T3 fibroblasts. In vitro, rhoGAP has a striking preference for G25K as a substrate, whilst p190GAP has marked preferential activity for rho. Furthermore, p190 preferentially inhibits rho-mediated stress fibre formation in vivo. Our data suggest that p190, rhoGAP and bcr play distinct roles in signalling pathways mediated through different rho family GTPases.

3T3 Cells↗