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[Analysis of sequence-tagged site in bcr and abl genes by DNA pooling and dHPLC].

To investigate the relationship between the single nucleotide polymorphism (SNPs) of the bcr and abl gene and chronic myelogeous leukemia (CML), the 9 sequence-tagged sites (STS) in bcr and abl gene were screened by DNA pooling and denaturing high performance liquid chromatography (dHPLC), and the results were varified by sequencing. The results showed that the polymorphism sites were detected in 4 out of the 9 STS fragments and there were 3 bases different from the reference sequence found in 3 fragments. In conclusion, the novel SNP in U07000 fragment shows significantly different frequencies between CML and controled people.

Chromatography, High Pressure Liquid↗

A novel mutation within the kinase domain of v-abl gene responsible for temperature-sensitive colony-forming ability in soft agar.

Mutation sites of unique temperature-sensitive (ts) mutants of Abelson murine leukemia virus(A-MuLV) that exhibited the ts phenotype in colony-forming ability in soft agar, but not in morphological transformation, were determined. Cloning and sequencing analysis of the full viral genomes of five independent ts mutants revealed a total of 10 mutation sites: 3 mutations (bp714, 742, and 817) located in the 5' untranslated region between LTR and gag gene; 4 mutations (bp1227, 1229, 1512, and 1634) in the gag gene; 3 mutations (point mutations at bp2764 and 3265, and 2-base deletion of bp3448 and 3449) in the abl gene. To determine the mutation sites critical for the ts phenotype in colony-forming ability in soft agar, hybrid viruses were constructed by exchanging the corresponding restriction fragments between wild-type and ts A-MuLV. The hybrid virus containing only the point mutation (T-->G) at bp2764 that exchanged leucine with arginine exhibited the ts phenotype in colony-forming ability in soft agar. Thus, a novel mutation within the kinase domain of the abl gene critical for the ts phenotype in colony-forming ability in soft agar was determined here.

3T3 Cells↗

[Rearrangement and expression of bcr-abl genes in CML and ALL].

We have carried out the molecular and cell-biological analysis on Ph1-positive leukemias in this study. Five out of nine Ph1-positive ALL cases showed molecular rearrangement within the classical bcr sequence (or M-bcr), similar as those in 47 CML cases. We examined 4 cases of Ph1-positive ALL presenting no rearrangement of M-bcr and found that, in 2 of 4 cases, one showed the breakpoint in a 5 kb segment of the bcr gene first intron (bcr-2) and the other in bcr-1, 16 kb upstream of bcr-2. Ph1-positive ALL frequently showed biphenotypical or biclonal phenotypes of myeloid and lymphoid lineages. Furthermore, we demonstrated the ability of two Ph1-positive ALL cell lines to differentiate into monocytic lineage in vitro, thus suggesting the possibility that these Ph1-positive ALL cells might reside on the stage of multipotent stem cell along the hematopoietic cell differentiation. Two out of 31 CML cases showed the mutations of the ras genes by the polymerase chain reaction; one case in the crisis phase and the other in the chronic phase. However, no mutations of the fms genes was detected. Two cases in the crisis phase of 24 CML patients (11 cases in the chronic phase and 13 cases in the crisis phase) contained rearrangements of the p53 gene by Southern analysis. Furthermore, the transcriptional alteration was found in 2 CML-BC and 2 CML-BC derived cell lines' samples, suggesting a important role of the p53 gene in the transformation of CML into the crisis phase.

Chromosome Fragility↗

[Inhibitory effect of siRNA on bcr-abl gene expression in K562 cell line].

To explore a new way to treat CML, inhibitory effect of small interfering RNA (SiRNA) on bcr-abl fusion gene expression of K562 cell line was studied. SiRNA for bcr-abl gene was designed and transfected into K562 cells, bcr-abl gene expression was tested by RT-PCR. The results showed that bcr-abl gene expression was inhibited by using siRNA in dose-dependent manner and reduced to 19.9% and 26.6% of the control at 24 and 48 hours after transfection with 0.2 micro g siRNA respectively. K562 cells proliferation was suppressed finally, but bcr-abl gene expression restored at 72 hours. In conclusion, anti-bcr-abl siRNA can effectively inhibit bcr-abl gene expression of K562 cell line.

Dose-Response Relationship, Drug↗

In vitro drug resistance to imatinib and mutation of ABL gene in childhood Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia.

Imatinib, the ABL kinase inhibitor, is used not only for Philadelphia chromosome-positive (Ph + ) chronic myelogenous leukemia, but also for Ph + acute lymphoblastic leukemia (ALL), although resistance to the drug tends to develop in an early stage of the clinical course. We describe a childhood refractory Ph + ALL patient in whom progressive resistance to imatinib was correlated with the appearance of a mutation in the BCR-ABL kinase domain and in vitro drug resistance to imatinib as determined by the methyl-thiazol-tetrazolium (MTT) assay. A missense mutation of T to C (Y253H) of the ABL gene was identified in the resistant clone, suggesting that this mutation may play an etiological role in the rapid loss of drug sensitivity.

Benzamides↗

Immunocytochemical evaluation of abl-gene products in leukemic cell lines.

We raised monoclonal antibody (MAb) against a synthetic oligopeptide corresponding to a portion of the predicted v-abl protein sequence (379-390). This MAb reacted with all of the abl-gene products (p145c-abl, p150c-abl and p210bcr-abl fused protein) and was not specific for any one of them. Immunocytochemically, we investigated the expression and localization of the abl-gene products in various leukemic cell lines. Positive immunoreactions were observed in Ph1 positive leukemic cell lines (K562 and KU-812) and erythro-leukemic cell lines (HEL and K3D) and were located on the cell membrane. Electron microscopically, a different distribution pattern was observed among the cell lines: linear and almost even in Ph1 positive leukemic cell lines, whereas spotted or budding-like in erythroleukemic cell lines. Ph1 translocation produces p210bcr-abl fused protein with not only altered autophosphorylation activities but also altered subcellular distribution patterns.

Animals↗

Establishment and characterization of A novel Philadelphia-chromosome positive chronic myeloid leukemia cell line, TCC-S, expressing P210 and P190 BCR/ABL transcripts but missing normal ABL gene.

A novel Philadelphia-chromosome positive (Ph+) cell line, TCC-S, has been established from a patient with Ph+ chronic myeloid leukemia (CML) in the blastic crisis. TCC-S cells were shown to express both P210 and P190 BCR/ABL transcripts by reverse transcriptase-polymerase chain reaction (PCR), although quantitative-PCR revealed that TCC-S cells mainly expressed P210 BCR/ABL transcript. Karyotype analysis revealed several triploid clones which constantly harbored two der(9)del(9) (p12)t(9;22) (q34;qll)s and two del(9) (q21)s. The der(9)del(9) (p12)t(9;22) (q34;q11) is rarely found in other CML cell lines. Moreover, to the best of our knowledge, del(9) (q21) resulting in missing of a restrict region including normal ABL gene has not been found among CML cell lines previously described. Thus, TCC-S cells with only BCR/ABL gene and no normal ABL gene may be a useful tool for functional study of ABL in Ph+ CML.

Blast Crisis↗

A 76-kb duplicon maps close to the BCR gene on chromosome 22 and the ABL gene on chromosome 9: possible involvement in the genesis of the Philadelphia chromosome translocation.

A patient with a typical form of chronic myeloid leukemia was found to carry a large deletion on the derivative chromosome 9q+ and an unusual BCR-ABL transcript characterized by the insertion, between BCR exon 14 and ABL exon 2, of 126 bp derived from a region located on chromosome 9, 1.4 Mb 5' to ABL. This sequence was contained in the bacterial artificial chromosome RP11-65J3, which in fluorescence in situ hybridization experiments on normal metaphases was found to detect, in addition to the predicted clear signal at 9q34, a faint but distinct signal at 22q11.2, where the BCR gene is located, suggesting the presence of a large region of homology between the two chromosomal regions. Indeed, blast analysis of the RP11-65J3 sequence against the entire human genome revealed the presence of a stretch of homology, about 76 kb long, located approximately 150 kb 3' to the BCR gene, and containing the 126-bp insertion sequence. Evolutionary studies using fluorescence in situ hybridization identified the region as a duplicon, which transposed from the region orthologous to human 9q34 to chromosome 22 after the divergence of orangutan from the human-chimpanzee-gorilla common ancestor about 14 million years ago. Recent sequence analyses have disclosed an unpredicted extensive segmental duplication of our genome, and the impact of duplicons in triggering genomic disorders is becoming more and more apparent. The discovery of a large duplicon relatively close to the ABL and BCR genes and the finding that the 126-bp insertion is very close to the duplicon at 9q34 open the question of the possible involvement of the duplicon in the formation of the Philadelphia chromosome translocation.

Animals↗

bcr rearrangement and C-abl gene expression in Ph1-positive hybrid acute leukemia with simultaneous proliferation of lymphoid and myeloid blasts.

bcr gene rearrangement and c-abl gene expression were analyzed in a patient with Philadelphia chromosome (Ph1)-positive hybrid acute leukemia with simultaneous proliferation of lymphoid and myeloid blasts. These data were compared with those from a patient with chronic myelogenous leukemia (CML) in mixed crisis. The leukemic cells of both patients showed immuno-phenotypic profiles such as non-T, non-B common ALL with some MPO-positive leukemic cells and rearranged JH genes. On analysis of molecular events associated with the Ph1 chromosome, the leukemic cells of a patient with CML in mixed crisis showed bcr rearrangement and an 8.5-kb bcr-abl chimeric mRNA, but those of a patient with Ph1-positive hybrid acute leukemia showed no 8.5-kb bcr-abl mRNA, as previously reported in a number of Ph1-positive acute lymphoblastic leukemia (ALL) cases. These results revealed that the molecular event found in Ph1-positive ALL is not only restricted to lymphoid lineage but may play an important role in the proliferation of the myeloid lineage.

Adult↗

Chromosomal breakpoints within the first intron of the ABL gene are nonrandom in patients with chronic myelogenous leukemia.

Bone marrow cells from 37 patients with chronic myelogenous leukemia (CML), who had the characteristic Philadelphia chromosome in their leukemic cells, were examined for ABL gene rearrangement by pulsed-field gel electrophoresis. By using several probes from the ABL gene, we found that in 33 of 37 (89%) patients studied, the translocation breakpoints in ABL fell within the 175-kilobase (kb) intron between exons 1b and 1a. Furthermore, breakpoints in this intron clustered in three regions, approximately 30 +/- 5, 100 +/- 13, and 135 +/- 8 kb downstream from exon 1b. These findings suggest that there may be specific sequences in this intron that facilitate the processes of chromosomal translocation.

Blotting, Southern↗

Ribozyme-mediated inhibition of bcr-abl gene expression in a Philadelphia chromosome-positive cell line.

The bcr-abl fusion gene is the molecular counterpart of the Philadelphia chromosome (Ph1) and is directly involved in the pathogenesis of Ph1+ leukemia. Inhibition of bcr-abl gene expression may have profound effects on the cell biology of Ph1+ cells, as recent experiments with antisense oligonucleotides have shown. In this study we have designed and synthesized a unique ribozyme that is directed against bcr-abl mRNA. The ribozyme cleaved bcr-abl mRNA in a cell-free in vitro system. A DNA-RNA hybrid ribozyme was then incorporated into a liposome vector and transfected into EM-2 cells, a cell line derived from a patient with blast crisis of chronic myelogenous leukemia. The ribozyme decreased levels of detectable bcr-abl mRNA in these cells, inhibited expression of the bcr-abl gene product, p210bcr-abl, and inhibited cell growth. This anti-bcr-abl ribozyme may be a useful tool to study the cell biology of Ph1+ leukemia and may ultimately have therapeutic potential in treating patients with Ph1 leukemias.

Base Sequence↗

A study on the incidence of ABL gene deletion on derivative chromosome 9 in chronic myelogenous leukemia by interphase fluorescence in situ hybridization and its association with disease progression.

Fluorescence in situ hybridization for the BCR/ABL rearrangement in 138 bone marrow specimens from 59 Philadelphia(+) (Ph(+)) chronic myelogenous leukemia (CML) patients, 35 Ph(+) acute lymphoblastic leukemia (ALL) patients, and 57 Ph(-) ALL patients was used. Sixteen (27.1%) of the 59 CML patients had deletions of the residual ABL gene on the derivative chromosome 9. During the study period, 32 of the 59 CML patients progressed to blast crisis or accelerated phase. Of these, nine patients had residual ABL gene deletions on the derivative chromosomes 9 and 23 patients had no deletions. The mean duration from first diagnosis to blast crisis or accelerated phase for the nine patients with ABL deletions was 32.8 months, and for the 23 patients without ABL deletions, it was 62.4 months (P = 0.017). The overall survival time for the 16 patients with deletions was 32.8 months, and for the 43 patients without deletions, it was 60.1 months (P = 0.164). ABL deletions were not detected among the 35 ALL patients (17 with major BCR/ABL, 18 with minor BCR/ABL), and it appears that this deletion occurs rarely or not at all in Ph(+) ALL patients, which is in contrast to the CML patients (27.1%). However, we detected two ALL cases with ABL deletion but without BCR/ABL rearrangement among 49 Ph(-) ALL and 66 Ph(-) AML patients. In conclusion, patients with ABL deletions progress to blast crisis or accelerated phase in a significantly shorter time than do those without such deletions. It is therefore suggested that the ABL deletion is an indicator of a poor prognosis in CML.

Acute Disease↗

[Second hematologic response and disappearance of the ABL gene mutant clone by cessation of imatinib in a CML patient with resistance to imatinib].

A seventy-six year old female patient with chronic myelogenous leukemia (CML), (chronic phase), was treated with imatinib and obtained a major cytogenetic response after 6 months of treatment. However, resistance to imatinib appeared 9 months later due to an ABL gene point mutation, and the patient's platelet count and BCR/ABL positive rate had remarkably increased. We discontinued imatinib and used IFNalpha or hydroxyurea, resulting in the disappearance of the ABL gene mutation clone. After that, we obtained a secondary hematologic response with the administration of imatinib.

Aged↗