Breakpoint characterization of der(9) deletions in chronic myeloid leukemia patients

Deletions adjacent to the 9/22 translocation breakpoint on the derivative chromosome 9 have recently been described in a substantial number of chronic myeloid leukemia (CML) cases, but their extension has not been characterized in detail. Using FISH with an appropriate set of BAC/PAC probes, we have characterized the deletion in 10 CML cases, identified by screening 71 patients at diagnosis. Five patients showed a complex chromosome rearrangement and 3 of them were deleted. The size of the deletion was variable, ranging from few hundreds kb to 8 Mb. A minimally deleted region on both chromosomes 9 and 22 was identified and was found to contain the ASS gene on chromosome 9 and IGLL1 on chromosome 22.     

Molecular cytogenetic characterization of deletions on der(9) in chronic myelocytic leukemia

The t(9;22)(q34;q11), generating the Philadelphia chromosome, is found in more than 90% of patients with chronic myelocytic leukemia (CML). Deletions adjacent to the translocation breakpoint on the derivative chromosome 9 have been described by several groups. These studies revealed two primary points: (1) genomic microdeletions were concomitant with the t(9;22) rearrangement; and (2) the location of the deleted sequence was centromeric to ABL and telomeric to BCR genes. We report on a detailed molecular cytogenetic characterization of chromosomal rearrangements in two CML patients bearing a complex variant t(9;22) and insertions of chromosome 22 sequences in 9q34. Our study shows that the location of the deleted sequences was downstream of the ABL gene and that genomic microdeletions were concomitant with the ins(9;22)(q34;q11q11) rearrangement.     

Clinical implications of der(9q) deletions detected through dual-fusion fluorescence in situ hybridization in patients with chronic myeloid leukemia

Poor outcomes of some chronic myeloid leukemia ((CML) patients have been associated with submicroscopic der(9q) deletions, particularly the 5'ABL region. Deletion profiles of 120 BCR/ABL+ CML patients were studied using the dual-fusion fluorescence in situ hybridization probe. Poor prognosis was associated with 5'ABL deletion but not with 3'BCR deletion. Overall survival (OS) and chronic phase duration (CPD) were significantly shorter for 5'ABL deletion than for those without deletions (OS time: 27 vs. 61 months, P = 0.02; CPD: 17 vs. 56 months, P = 0.02). In addition, when isolated 5'ABL deletion patients were compared to those without it, a greater impact on prognosis was detected (OS time: 18 vs. 59 months, P = 0.0008; CPD: 7 vs. 54 months, P = 0.0003). Isolated 5'ABL deletion seems to have a greater impact on survival than does concomitant 5'ABL and 3'BCR deletion, although the difference was not statistically significant in this aspect (OS time: 18 vs. 28 months, P = 0.08).     

Genomic deletions on other chromosomes involved in variant t(9;22) chronic myeloid leukemia cases

The Philadelphia (Ph) chromosome is the cytogenetic hallmark of chronic myeloid leukemia (CML) and is observed in more than 90% of CML cases. At diagnosis, in 5-10% of CML patients the Ph chromosome is derived from variant translocations other than the standard t(9;22). Deletions adjacent to the translocation junction on the derivative chromosome 9 were recently described by different groups. The deletions may identify a subgroup with a worse prognosis. The presence of similar deletions on the third derivative other than the 9 and 22 chromosomes in CML with variant translocation has never been investigated. We studied three cases of CML variants showing relatively large deletions on the third chromosome involved in the translocation. Known tumor-suppressor genes (TSGs) or genes involved in signal transduction and in the modulation of cell proliferation were found to be located inside these deleted regions. As an alternative to Knudson's two-hit model, the "haplo-insufficiency" hypothesis suggests that the deletion of a single allele of a TSG can play an important role in tumor progression. Our findings suggest that great attention should be paid to the molecular cytogenetic characterization of variant t(9;22) CML patients to unveil fully the biological heterogeneity of CML.     

Near-haploid cell line in megakaryoblastic transformation of Philadelphia-positive chronic myeloid leukemia

A case of near haploidy in a patient with an acute megakaryoblastic transformation of Philadelphia (Ph)-positive chronic myeloid leukemia (CML) was studied. Cytogenetic studies revealed persistence of a Ph-positive pseudodiploid cell line and the emergence of a Ph-positive near-haploid cell line, i.e., 46,XX,t(9;22)(q34;q11)/28,XX,t(9;22),+8,+14,+18,+29. The near-haploid cell line is a rare cytogenetic finding. The patient rapidly deteriorated and died.     

Cytogenetic follow-up after bone marrow transplantation for Philadelphia-positive chronic myeloid leukemia

Forty-eight consecutive patients affected by chronic myelogenous leukemia (CML) Philadelphia (Ph) chromosome positive during the chronic phase of the disease underwent allogeneic bone marrow transplantation (BMT). Thirty-five patients had a follow-up over 12 months and were included in a cytogenetic study in order to evaluate the Ph clone eradication. In 25 cases, the Ph chromosome disappeared in all cytogenetic studies, and their hematologic picture is at present apparently normal. Ten patients showed cytogenetic relapse. In one case, the cytogenetic relapse was transitory without any clinical sign of the disease; in three cases, after a transitory cytogenetic relapse, a persistent relapse with clinical picture of progression of the disease occurred; in six cases cytogenetic and a clinical relapse were coincident. Structural chromosomal abnormalities other than Ph were temporarily seen in three cases. The so-called "nonrandom" chromosomal changes typical of the blastic phase were never detected. The reappearing Ph-positive clone spontaneously disappeared in three patients, and their hematologic picture reverted to complete chimerism. The present study confirms that the eradication of the Ph clone is often defective with BMT, and cytogenetic analysis can detect the competition between donor and residual host marrow. Furthermore, the karyotype evolution is different from that found in CML patients treated with conventional chemotherapy.     

Derivative chromosome 9 deletions in chronic myeloid leukaemia: interpretation of atypical D-FISH pattern

BACKGROUND/AIMS: New molecular cytogenetic techniques are increasingly applied as a routine investigative tool in haematological malignancies, both at diagnosis and subsequent monitoring. This report describes the interpretation of atypical signal patterns encountered using BCR-ABL dual colour dual fusion fluorescence in situ hybridisation (D-FISH) translocation probes in chronic myeloid leukaemia (CML). METHODS: Interphase FISH experiments were carried out using BCR-ABL D-FISH probes in 46 patients with CML at diagnosis and during subsequent disease monitoring. Atypical hybridisation signal patterns were characterised by molecular cytogenetic techniques and correlated with conventional karyotyping. RESULTS: Two patients showed atypical interphase D-FISH patterns with one orange, one green, and one fusion (1O1G1F) signal. The presence of BCR-ABL gene fusion was documented by a dual colour single fusion (S-FISH) probe. The submicroscopic deletion of the ABL-BCR fusion gene on the derivative chromosome 9 in these cases was subsequently characterised by metaphase FISH on relocated G banded metaphases. CONCLUSIONS: Atypical interphase D-FISH patterns should not be interpreted in isolation and should be considered in conjunction with other cytogenetic or molecular genetic investigations.     

Translocation t(9;9)(p13;q34) in Philadelphia-negative chronic myeloid leukemia with breakpoint cluster region rearrangement

Chromosome analysis showed a t(9;9)(p13;q34) in a patient with chronic myeloid leukemia (CML) without a Philadelphia (Ph) chromosome in all examined cells. Southern blot analysis of leukocyte DNA revealed rearrangement of breakpoint cluster region (bcr) within the 5.8-kb bcr sequences as in Ph-positive CML patients. The findings confirm that the 9q34 and 22q11 bands are always involved in CML independent of the chromosomal evidence. It is suggested that Ph-negative bcr-positive CML may have variant translocations, as in the case of the t(9;9) reported here.     

Molecular cytogenetic characterization of a complex rearrangement involving chromosomes 9 and 22 in a case of Ph-negative chronic myeloid leukemia

The "golden path", produced by the Human Genome Project effort, is composed of a collection of overlapping and fully sequenced BAC/PAC clones covering almost completely the human genome. These clones can be advantageously exploited as fluorescence in situ hybridization (FISH) probes for the characterization of rearrangements frequently found in tumors. Breakpoint characterization can be further refined by generating additional smaller FISH probes through LONG-PCR amplification of specific DNA segments, 5-10 kb in size, using appropriate BAC/PAC probes as template. We report here an example of this approach that has been used to characterize a complex Ph-negative chronic myeloid leukemia (CML Ph-) case in which the BCR/ABL fusion gene was found located on chromosome 9.     

Prognosis in chronic myeloid leukemia]

The clinical course of patients with chronic myelogenous leukaemia (CML) is very heterogenous. Survival is determined by the timing of disease transformation. A patient's risk of transformation can be defined, but the time when it will occur can not be predicted. A number of features recorded at the time of diagnosis correlate significantly with survival and can serve as prognostic parameters. Conventional therapy has not achieved a substantial delay in the universally fatal outcome of the disease. Allogenic or syngenic bone marrow transplantation to individuals with CML is at present the only treatment with a curative potential.