A three way complex translocation (4; 9; 22) in two patients with chronic myelocytic leukemia

Chronic myeloid leukemia (CML) is genetically characterized by the reciprocal translocation of chromosome 9 and 22, t(9;22)(q34;q11) which results in the fusion of BCR/ABL gene observed on the derivative chromosome 22 called Philadelphia (Ph') chromosome. About 5-8% of Philadelphia positive patients with CML show various complex translocations involving third chromosome in addition to chromosome 9 and 22. In present report we discuss two cases with CML referred at our centre. At the time of initial diagnosis and after 9 months of treatment, one of the patients showed 100% presence of Philadelphia positive in bone marrow culture. During follow-up in an accelerated state, his cytogenetic study revealed a complex translocation (4;9;22)(q25;q34;q11) along with an additional Philadelphia and marker chromosome. The second patient showed a complex (4;9;22)(q25;q34;q11) translocation at the time of diagnosis. He was on hydroxyurea and his follow-up cytogenetic study after the course of chemotherapy showed no changes. Further confirmation of complex translocation was done by FISH study using bcr/abl and whole chromosome 9 probes. Though the additional genes involved in complex variant Ph' rearrangements have not been characterized, both patients are healthy till 3 to 5 years of initial diagnosis. This could be attributed to the benign effect resulted from reciprocal translocation with no loss or gain of the genetic material.     

Insertion of the 3' ABL region into the long arm of chromosome 1 in a Philadelphia chromosome-negative chronic myeloid leukemia case

Chronic myeloid leukemia (CML) is a pluripotent hematopoietic stem cell disorder almost always characterized by the presence of the Philadelphia chromosome (Ph), usually due to t(9;22)(q34;q11). The presence of Ph results in the formation of the BCR/ABL fusion gene, which is a constitutively activated tyrosine kinase. Approximately 1% of CML patients appear to have a Ph-negative karyotype but carry a cryptic BCR/ABL fusion that can be located by fluorescence in situ hybridization (FISH) at chromosome 22q11, 9q34 or a third chromosome. This study investigated a rare Ph-negative CML case with insertion of the 3' ABL region into the long arm of derivative chromosome 1 but lacking the 5' BCR region on der(22).     

The finding of a reciprocal whole-arm translocation t(X;12)(p10;p10) in association with atypical chronic myeloid leukaemia

Atypical chronic myeloid leukaemia (aCML) belongs to the myeloproliferative/myelodysplastic category of haematological disease. Main characteristics are marked dysgranulopoiesis, bone marrow dysfunction and the failure to demonstrate the presence of the Philadelphia chromosome or BCR/ABL fusion gene normally associated with CML t(9;22)(q34;q11). It carries a poor prognosis with limited therapeutic options available. Most cases of aCML have one or more karyotypic abnormalities. We highlight a clinical presentation of aCML associated with an acquired reciprocal whole-arm translocation (WAT), t(X;12)(p10;p10), which to our knowledge has not yet been described. We also discuss how such a translocation might lead to tumorigenesis.     

A new complex variant Philadelphia chromosome, t(1;9;22)ins(17;22), characterized by fluorescence in situ hybridization in an adult ALL

A new complex variant Philadelphia chromosome was detected in a 65-year-old man with acute, pre-B, lymphoblastic leukemia (ALL). The classic cytogenetic analysis identified an apparently balanced three-way translocation t(1;9;22)(q25;q34;q11.2). Fluorescence in situ hybridization (FISH) studies confirmed the translocation and showed bcr/abl fusion on the der(22). However, these studies revealed that the distal part of the bcr gene was not translocated onto chromosome 1 at 1q25, but inserted into chromosome 17 at 17p12-13. This complex variant translocation was described as a t(1;9;22)(q25;q34;q11.2)ins(17;22)(p12-13;q11.2q11.2). Secondary changes including +8, an inversion of the derivative chromosome 9, a translocation t(14;20)(q11;q13), and an additional derivative 22 were also identified in most of the abnormal cells. The patient died from systemic fungemia and multiorgan failure 9 months after the diagnosis of ALL. The clinical significance of complex variant Philadelphia chromosomes in ALL is reviewed and discussed.     

BCR translocation to derivative chromosome 2: a new case of chronic myeloid leukemia with a complex variant translocation and Philadelphia chromosome

The well-known typical fusion gene BCR/ABL is observed in connection with a complex translocation event in 5-8% of cases of chronic myeloid leukemia (CML). The present study described an exceptional CML case with complex chromosomal aberrations not previously observed. Aberrations included a translocated BCR to the derivative chromosome 2 [der(2)] that also involved a four-chromosome translocation, implying chromosomal regions 1p32 and 2q21, besides 9q34 and 22q11.2, which were characterized by molecular cytogenetics.     

Non random distribution of genomic features in breakpoint regions involved in chronic myeloid leukemia cases with variant t(9;22) or additional chromosomal rearrangements

Background  

The t(9;22)(q34;q11), generating the Philadelphia (Ph) chromosome, is found in more than 90% of patients with chronic myeloid leukemia (CML). As a result of the translocation, the 3' portion of the ABL1 oncogene is transposed from 9q34 to the 5' portion of the BCR gene on chromosome 22 to form the BCR/ABL1 fusion gene. At diagnosis, in 5-10% of CML patients the Ph chromosome is derived from variant translocations other than the standard t(9;22).     

A rare case of Philadelphia chromosome-positive chronic myelogenous leukemia with inversion in chromosome 9 and t(10;17)

The reciprocal translocation t(9;22)(q34;q11), leading to the formation of two fusion genes, BCR/ABL and ABL/BCR, is found in 90-95% of cases with chronic myeloid leukemia (CML). ABL-BCR expression does not correlate with prognosis, as assessed by cytogenetic response, since the ABL/BCR gene is expressed in only a proportion of CML patients. This study examined an exceptional BCR/ABL-positive CML case with inversion in 9q22q34 leading to the absence of ABL/BCR. Moreover, an unbalanced translocation between chromosomes 10 and 17 which caused deletion of the TP53 gene was identified. The TP53 gene plays a potential role in CML progression, and loss of TP53 may be regarded as a poor prognostic factor.     

Philadelphia chromosome-positive chronic myelogenous leukemia with deleted fusion of BCR and ABL genes

In the great majority of patients with chronic myelogenous leukemia (CML) the reciprocal translocation between chromosomes 9 and 22, t(9;22)(q34;q11), resulting in the Philadelphia (Ph) chromosome produces fusion DNA sequences consisting of the 5' part of the major breakpoint cluster region-1 (M-BCR-1) and the ABL protooncogene which encodes for the P210BCR-ABL phosphoprotein with tyrosine kinase activity implicated in the pathogenesis of CML. Molecular analysis was performed on 25 patients with Ph-positive CML using 2 breakpoint cluster region (bcr) probes within the M-BCR-1 DNA sequences, and two of them did not contain either detectable rearranged DNA homologous to the 5' side bcr probe or ABL-related fusion mRNA. The chromosomal in situ hybridization technique revealed that these two Ph-positive CML cases did not carry DNAs homologous to the 5' bcr or ABL probes on the Ph chromosome. Furthermore, one of the two Ph-positive CML cases did not show either rearranged DNA or regions homologous to the 3' bcr probe on a 9q+ chromosome, while the other CML case showed a rearrangement detected by the 3' bcr probe and transposition of the 3' bcr homologous to the 9q+ chromosome. Thus, the possibility is raised that the BCR/ABL fusion DNA has been deleted in rare CML cases, and that the deletion possibly occurred in a stepwise manner following the formation of the Ph chromosome at any stage of the disease.     

Derivative chromosome 9 deletions are a significant feature of childhood Philadelphia chromosome positive acute lymphoblastic leukaemia.

Deletions from the derivative chromosome 9, der(9), of the translocation, t(9;22)(q34;q11), at the site of the ABL/BCR fusion gene, have been demonstrated by fluorescence in situ hybridisation (FISH), in both Philadelphia chromosome (Ph)-positive chronic myeloid leukaemia (CML) and acute lymphoblastic leukaemia (ALL). In CML they occur in 10-15% of cases and appear to indicate a worse prognosis, whereas in ALL, the situation is unclear. This study presents the findings of dual fusion FISH used to detect such deletions in a series of 27 BCR/ ABL-positive childhood ALL patients. Metaphase FISH was essential for the accurate interpretation of interphase FISH signal patterns. Three cases (11%) had a single fusion signal, resulting from deletions of the der(9). Three other patients with variant translocations and one with an insertion, also had a single fusion, but with no evidence of deletions. Gain of a fusion in approximately one-third of patients indicated a second Ph, which appears to be a diagnostic marker of Ph-positive ALL. This study shows that the incidence of deletions from the der(9) in childhood ALL is at least as high as that reported for CML.     

Atypical BCR and ABL D-FISH patterns in chronic myeloid leukemia and their possible role in therapy.

D-FISH uses DNA probes with fluorescence in situ hybridization to detect two fusion signals in cells with a t(9;22)(q34;q11.2) from patients with chronic myeloid leukemia (CML). Using D-FISH, 147 patients with CML were studied and considerable macro genetic variation was observed among their Ph-chromosomes. Typical D-FISH signal patterns were observed for 81% of patients, but three different atypical patterns were seen in 19% of patients. Atypical patterns among Ph-chromosomes were consistent with loss of the 3' portion of BCR that is usually translocated to chromosome 9, or loss of the 5' segment of ABL that usually remains on chromosome 9, or loss of both the 3' translocated BCR and 5' residual ABL hybridization sites. Atypical patterns were associated with all forms of Ph-chromosomes including t(9;22)(q34;q1.2), complex translocations and masked. The normal range for 500 interphase nuclei for patients with typical patterns is < 1%. By comparison, the normal range for patients with either of two atypical patterns was < or = 1.8% and for patients with the other atypical pattern was < or = 23%. Thus, special scoring criteria are needed to detect and quantify nuclei with atypical patterns using D-FISH. The proportion of patients that responded to therapy with interferon alpha-2b or interferon alpha-2b and ara-C for 36 patients with typical patterns was similar to 7 patients with atypical patterns.     

Ph-Negative Chronic Myeloid Leukemia: The Nature of the Breakpoint Junctions and Mechanism of ABL Transposition

CML is a well-defined hematological and clinical entity which sooner or later progresses to blast crisis and death of the patient. Leukemic cells of about 95% of patients show the Ph chromosome which is evidence of the t(9;22)(q34;q11), the cytogenetic rearrangement whereby the BCR gene on chromosome 22 and the ABL gene on chromosome 9 are joined together. The juxtaposition of these genes deregulates the usual function of ABL and causes leukemia. Leukemic cells of the remaining 5% (approximate) of CML patients show complex translocations or have a normal karyotype. Complex translocations achieve the same juxtaposition of BCR and ABL as the standard t(9;22). The Ph chromosome is usually present but may be masked. The final result of a complex translocation can be an apparently normal karyotype and, although BCR and ABL are juxtaposed, there is no Ph chromosome. This is the origin of some cases of Ph-negative CML, in others, part of chromosome 9 including ABL is inserted within the BCR gene. We believe that simple and complex recombinations and insertions are each caused by a single concerted event which breaks a number of adjacent DNA strands at the same time, followed by their mismatched joining and consequent recombination.

The association of BCR-ABL is the essential etiological feature of CML and can be explained, in all cases investigated, by chromosomal rearrangement which takes the form of simple or complex translocations or chromosome insertion. Events that initiate chromosome rearrangement are therefore important in the etiology of CML. Chromosome rearrangement is the result of abnormal DNA recombination which may be caused by an error in normal recombination processes or by endogenous and exogenous mutagens such as chemicals or radiation. These can be regarded as the prime causes of CML.     

Detection of BCR/ABL Fusion Gene by Hematological and Cytogenetical Analysis in Chronic Myeloid Leukemia Patients in Quetta,Pakistan

Background: Chronic myeloid leukemia (CML) is a myeloproliferative disorder of pluripotent stem cells,caused by reciprocal translocation between the long arms of chromosomes 9 and 22, t(9;22)(q34;q11), known asthe Philadelphia chromosome. Materials and Methods: A total of 51 CML patients were recruited in this study.Complete blood counts of all CML patients were performed to find out their total leukocytes, hemoglobin andplatelets. FISH was performed for the detection of BCR-ABL fusion and cryptogenic tests using bone marrowsamples were performed for the conformation of Ph (9;22)(q34;q11) and variant translocation mechanisms.Results: In cytogenetic analysis we observed that out of 51 CML patients 40 (88.9%) were Ph positive and 4(8.88%) had Ph negative chromosomes. Mean values of WBC 134.5 103/μl, hemoglobin 10.44 mg/dl, and platelets288.6 103/μl were observed in this study. Conclusions: In this study, Ph positive translocation between chromosome(9:22)(q34;q11) were observed in 40 (88.9%) CML patients.     

Philadelphia Chromosome-positive Chronic Myelogenous Leukemia with Deleted Fusion of BCR and ABL Genes

In the great majority of patients with chronic myelogenous leukemia (CML) the reciprocal translocation between chromosomes 9 and 22, t(9;22)(q34;q11), resulting in the Philadelphia (Ph) chromosome produces fusion DNA sequences consisting of the 5′ part of the major breakpoint cluster region-1 (M-BCR-1) and the ABL protooncogene which encodes for the P210^BCR-ABL phosphoprotein with tyrosine kinase activity implicated in the pathogenesis of CML. Molecular analysis was performed on 25 patients with Ph-positive CML using 2 breakpoint cluster region (bcr) probes within the M-BCR-1 DNA sequences, and two of them did not contain either detectable rearranged DNA homologous to the 5′ side bcr probe or ABL-related fusion mRNA. The chromosomal in situ hybridization technique revealed that these two Ph-positive CML cases did not carry DNAs homologous to the 5′bcr or ABL probes on the Ph chromosome. Furthermore, one of the two Ph-positive CML cases did not show either rearranged DNA or regions homologous to the 3′bcr probe on a 9q+ chromosome, while the other CML case showed a rearrangement detected by the 3′bcr probe and transposition of the 3′bcr homologous to the 9q+ chromosome. Thus, the possibility is raised that the BCR/ABL fusion DNA has been deleted in rare CML cases, and that the deletion possibly occurred in a stepwise manner following the formation of the Ph chromosome at any stage of the disease.     

t(9;22)(q34;q11.2) is a recurrent constitutional non-Robertsonian translocation and a rare cytogenetic mimic of chronic myeloid leukemia

The diagnosis of hematologic malignancy can be greatly aided by the detection of a cytogenetic abnormality. However, care must be taken to ensure that constitutional chromosomal abnormalities are not misattributed to a putative population of malignant cells. Here we present an unusual case in which a constitutional balanced t(9;22)(q34;q11.2) cytogenetically mimicked the acquired, t(9;22)(q34;q11.2), that is characteristic of chronic myeloid leukemia. Of special note, fluorescence in situ hybridization (FISH) analysis for this constitutional translocation (9;22)(q34;q11.2) using standard probes for BCR and ABL1 resulted in an abnormal pattern that was potentially misinterpretable as a BCR-ABL1 fusion. This is the first reported FISH analysis of a constitutional t(9;22)(q34;q11.2), and overall only the second report of such an abnormality. In light of the isolated prior report, our case also suggests that the constitutional t(9;22)(q34;q11.2) is one of the very few?recurrent constitutional non-Robertsonian translocations described in humans. Our case underscores the necessity of complete clinical and laboratory correlation to avoid misdiagnosis of myeloid malignancy in the setting of rare constitutional cytogenetic abnormalities.     

Adult precursor B-ALL with BCR/ABL gene rearrangements displays a unique immunophenotype based on the pattern of CD10, CD34, CD13 and CD38 expresssion.

The Philadelphia chromosome (Ph+) reflects a balanced reciprocal translocation between the long arms of chromosomes 9 and 22 [t(9;22)(q34;q11.2] involving the BCR and ABL genes. At present, detection of BCR/ABL gene rearrangements is mandatory in precursor-B-ALL patients at diagnosis for prognostic stratification and treatment decision. In spite of the clinical impact, no screening method, displaying a high sensitive and specificity, is available for the identification of BCR/ABL+ precursor-B-ALL cases. The aim of the present study was to explore the immunophenotypic characteristics of precursor B-ALL cases displaying BCR/ABL gene rearrangements using multiple stainings analyzed by quantitative flow cytometry in order to rapidly (<1 h) identify unique phenotypes associated with this translocation. From the 82 precursor-B-ALL cases included in the study 12 displayed BCR/ABL gene rearragements, all corresponding to adult patients, four of which also displayed DNA aneuploidy. Our results show that BCR/ABL+ precursor B-ALL cases constantly displayed a homogeneous expression of CD10 and CD34 but low and relatively heterogeneous CD38 expression, together with an aberrant reactivity for CD13. In contrast, this unique phenotype was only detected in three out of 70 BCR/ABL cases. Therefore, the combined use of staining patterns for CD34, CD38 and CD13 expression within CD10-positive blast cells is highly suggestive of BCR/ABL gene rearrangements in adults with precursor B-ALL.