Chromosome and bcr rearrangement in chronic myelogenous leukaemia and their correlation with clinical states and prognosis of the disease

Differentiating juvenile myelomonocytic leukemia from chronic myeloid leukemia in childhood

Juvenile myelomonocytic leukemia (JMML) is a rare clonal myeloproliferative disease of early childhood. To determine the diagnostic features, appropriate treatment, and overall patient survival pertaining to JMML for children, the authors reviewed the clinical data of 16 children with JMML admitted to the National Taiwan University Hospital between 1978 and 2001. Median age at diagnosis was 2.5 years. Fever was the most common symptom at diagnosis. At initial presentation, the mean white blood count and absolute monocyte count were 30 x 10(9)/L and 4.5 x 10(9)/L, respectively. Cytogenetic analysis was performed in 14 patients, and 2 patients (14%) had monosomy 7. Another patient, with normal karyotype at diagnosis, had deletion of 7q22 at the follow-up chromosome study. Forty-seven chronic myeloid leukemia (CML) patients were also diagnosed and followed at the same hospital during the same interval period. The age, leukocyte counts, platelet counts, basophil counts, monocyte percentages on peripheral blood smears, and median survival rate showed significant differences between JMML and CML patients (P < 0.05). The median survival was 10 months and the probability of 10-month survival was 0.38 by Kaplan-Meier analysis for 12 of the 16 JMML patients who did not receive hematopoietic stem cell transplantation (HSCT). Among three patients receiving HSCT, one patient relapsed 9 months after the first HSCT and was treated successfully by a second HSCT from the same sibling donor.

Additional chromosomal abnormalities and variability of BCR breakpoints in Philadelphia chromosome/BCR-ABL-positive acute lymphoblastic leukemia in Taiwan

From 1986 to 1998, 26 (23%) of 114 adult acute lymphoblastic leukemia (ALL) patients and 11 (4%) of 328 pediatric patients were found to have Philadelphia (Ph) chromosome. In the 30 patients with available data at diagnosis, 18 (60%) had extra-chromosomal abnormalities. They included 1q duplication (5/18, 28%), supernumerary Ph chromosome (4/18, 22%), 9p abnormalities (3/18, 17%), 7q deletion/monosomy 7 (3/18, 17%), trisomy 19 (1/18, 6%), and trisomy 8 (1/18, 6%). Excluding those with specific cytogenetic changes, only one patient had hyperdiploid karyotype with more than 50 chromosomes. The incidence of 1q duplication was higher and that of hyperdiploidy was lower in this study than has been previously reported. There was no prognostic implication of these additional cytogenetic abnormalities. With fluorescence in situ hybridization (FISH) and reverse transcription-polymerase chain reaction (RT-PCR), 14 (27%) of 53 unselected adult ALL patients and 2 (5%) of 38 unselected pediatric patients were BCR-ABL-positive, including one adult and two children without Ph chromosome. The BCR-ABL fusion genes/transcripts were also present in all other 16 selected Ph-positive ALL patients. The BCR-ABL fusion subtypes were determined in all these 32 patients: 91% (11/12) childhood cases showed m-type fusion gene while 45% (9/20) adult ones did so (P = 0.0083). The clinical outcome was similar between the two groups of patients with m-type and M-type BCR-ABL. In conclusion, both cytogenetic and molecular studies are very helpful for identifying the subgroup of ALL patients with Ph/BCR-ABL. The additional cytogenetic abnormalities and subtypes of BCR-ABL fusion genes/transcripts had no significant implications in this group of patients.

BCR-ABL fusion peptides and cytotoxic T cells in chronic myeloid leukaemia

The BCR-ABL gene that arises in chronic myeloid leukaemia (CML) is a neoantigen. Peptides derived from the BCR-ABL fusion junction may therefore be immunogenic, if appropriately presented to the immune system. This article reviews data demonstrating that certain junctional peptides will bind to HLA molecules, and that these peptides will elicit specific T-lymphocyte responses in vitro, in both normal subjects and in CML patients. The clinical relevance of these observations is discussed.

[Tyrosine kinase: implications in tumor pathology and therapeutic perspectives]

The tyrosine kinase family includes growth factor receptor and cytoplasmic enzymes. It plays a key role in normal cell division and abnormal cell proliferation and differentiation. The most common tyrosine kinases are the epidermal-growth factor (EGFR) and platelet-derived growth factor (PDGF) receptors, and a chromosome Philadelphia product, the Bcr-abl oncogene. Many studies have attempted to correlate clinical evolution of tumors with tyrosine kinase expression. However, clinical application of these new prognostic factors has not yet been demonstrated. More recently, tyrosine-phosphorylation inhibitors (tryphostin) have been developed in phase I studies. Results that were obtained show some objective responses in patients with glioblastoma and polymetastatic cancer. Another approach to block tyrosine kinase expression is the use of monoclonal antibodies. Trials using such antibodies have shown interesting preliminary results.

Clinical relevance of the breakpoint sites within the M-BCR in 50 patients from Argentina with chronic myeloid leukemia

Fifty patients from Argentina with chronic myeloid leukemia (CML) were studied in order to characterize the breakpoint site within the major breakpoint cluster region (M-BCR) and its relationship with the duration of the chronic phase (CP). The DNA digestion with the restriction enzymes: Bgl II, BAM HI and Hind III and hybridization with the 1.2Kb Hind III-Bgl II bcr probe showed that 56% of cases had the breakpoint in 5'M-bcr region and the remaining 44% in 3'M-bcr region. The duration of chronic phase from diagnosis to the onset of the blast crisis (BC) was correlated with the location of the breakpoint within the M-bcr and no statistical differences were observed between the 5' and the 3' groups. These data indicate that the breakpoint site within the bcr gene is not a prognostic indicator of the duration of CP of the disease.

[Chronic myeloid leukemia, biological aspects]

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of a stem cell, involving myeloid, erythroid, megacaryocyte, lymphoid B-cells and "natural killer" cells. The hallmark of CML is the Philadelphia (Ph) chromosome which is a shortened chromosome 22 (22q-) resulting from a reciprocal translocation involving chromosome 9 and chromosome 22, designed t (9;22) (q34;q11). This translocation juxtaposes parts of two genes; ABL on chromosome 9 and BCR (breakpoint cluster region) on chromosome 22. Transcription of the BCR/ABL fusion gene results in an hybrid mRNA that is translated into a 210 kDa or 190 kDa protein, depending on the location of the breakpoint in the bcr region. This protein plays a key role in CML: its tyrosine-kinase activity, that differs from the normal ABL product, may be involved in leukemic cell growth. Nonetheless, the loss of the negative cell growth regulation by c-ABL, or BCR/ABL fusion protein interaction with other cellular genes (such as RAS or c-MYC) could also be involved in CML pathophysiology. A better understanding of the molecular mecanisms of CML could lead to specific treatment, such as tyrosine-kinase inhibitors, synthetic oligodeoxynucleotides, or site-specific DNA-binding proteins designed against BCR/ABL oncogenic fusion sequence.

Further evidence for the lack of correlation between the breakpoint site within M-BCR and CML prognosis and for the occasional involvement of p53 in transformation

The actual significance of the type of BCR-ABL rearrangement in chronic myeloid leukemia (CML) prognosis remains controversial. Also, the molecular events that lead to CML progression are largely unknown. We analyzed the M-BCR breakpoint position in 64 CML patients by Southern blot and correlated the molecular findings with the cytogenetic, hematologic, and clinical data. No statistically significant differences were found with respect to the clinical and hematologic data presented at diagnosis or in the median duration of chronic phase (CP) and survival between the groups of patients with 5' and 3' breakpoints. We also studied by PCR-SSCP and direct sequencing the p53 gene in patients with specimens available in both chronic phase and blast crisis. We identified p53 mutations in 17% of the blast crisis samples analyzed, whereas no abnormalities were found in CP. This finding suggests that only in a minor fraction of cases are lesions in the p53 gene involved in transformation. Given the present findings, along with previous reports, we believe that a novel mechanism to explain the heterogeneity of CML should be postulated and actively pursued, as should the identification of secondary molecular events more consistently involved in progression.

The breakpoint cluster region site in patients with Philadelphia chromosome-positive chronic myelogenous leukemia. Clinical, laboratory, and prognostic correlations

BACKGROUND

The breakpoint site of the breakpoint cluster region (bcr) has been correlated with patient characteristics, with the disease phase, and with the prognosis of patients with chronic myelogenous leukemia (CML), but the findings remain controversial.

METHODS

Appropriate restriction enzymes and the 3' and universal probes were used to map the breakpoint site by Southern blot analysis into 5' and 3' breakpoints and a breakpoint in zone 3 (or fragment 2) in 362 patients in different phases of CML (238 in early chronic phase, 69 in late chronic phase, 31 in accelerated phase, and 24 in blastic phase). Standard statistical methods were used to evaluate differences in characteristics and in prognosis by the breakpoint site.

RESULTS

No correlation was noted between CML phases and breakpoint site. Among patients in the early chronic phase, thrombocytosis was significantly associated with the 3' breakpoint site (P = 0.02), whereas peripheral basophilia occurred more frequently with the 5' breakpoint site (P = 0.05). Other patient and disease characteristics were similar in frequency among the breakpoint-site subgroups. There was no difference in response to alpha-interferon therapy (186 patients treated) by the breakpoint site. Survival, dated from either referral to the authors' institution or from diagnosis, was not significantly different among patients with early chronic phase CML by the breakpoint site. However, patients with a 3' deletion tended to have a shorter survival.

CONCLUSION

Determination of the breakpoint site by Southern blot analysis does not help to predict prognosis of patients with CML.

Analysis of molecular breakpoint and m-RNA transcripts in a prospective randomized trial of interferon in chronic myeloid leukaemia: no correlation with clinical features, cytogenetic response, duration of chronic phase, or survival

Two hundred and nineteen cases of Ph+ve CML and 15 Ph-ve, BCR+ve CML cases have been analysed to determine the breakpoint site and its relationship to clinical features, cytogenetic response, duration of chronic phase and survival. 119 cases have had RNA analysis performed to determine the type of BCR/ABL transcript and have also been analysed in a similar way. Presenting features at diagnosis including age, sex, white-cell count and platelet count showed no significant difference for those with 5' and 3' breakpoints and those with either b2a2 or b3a2 BCR/ABL transcripts. However, in a subgroup of patients whose presenting white-cell count was < 100 x 10(9)/l, those with b3a2 transcript did have a significantly higher platelet count. Analysis by Sokal risk grouping showed no difference for 5' or 3' breakpoints but a trend for lower stage among those with b2a2 transcripts. No correlation was found either for genomic breakpoint site or BCR/ABL RNA transcript in terms of duration of chronic phase or survival. When stratified by randomized therapy, either interferon-alpha or standard chemotherapy, no difference was noted in relation to genomic breakpoint site or BCR/ABL transcript. Cytogenetic response was not related to the molecular findings.

Does the type of BCR/ABL junction predict the survival of patients with Ph1-positive chronic myeloid leukemia?

The prognostic value of the site of DNA rearrangement within the M-BCR on chromosome 22 or of the type of transcript has been debated in the last years. The majority of the studies do not support the hypothesis of a predictive value of such molecular parameters. Results coming from a multicentric, prospective trial, based on alpha-IFN therapy, seem to indicate a better karyotypic response in 3' rearranged patients. The possibility of evoking a cytotoxic immune response directed towards peptides originating from each of the different BCR/ABL junctions constitute an important challenge for the future.

Comparison of clinical and biologic features between myeloid and lymphoid transformation of Philadelphia chromosome positive chronic myeloid leukemia

Analysis of clinical and biologic features of chronic myeloid leukemia (CML) in blast crisis (BC) was performed on 36 patients: 25 had myeloid and 11 had lymphoid transformation. The median duration from diagnosis to onset of BC was significantly shorter in patients with lymphoid BC (6 months) than in those with myeloid BC (41 months). Patients in lymphoid transformation showed better response to therapy and had a significantly longer median survival time after BC than patients with myeloid transformation (56% vs 0% and 10 months vs 4 months, respectively). The leukemic cells from all the patients with lymphoid BC showed B-cell immunophenotype, confirmed by the presence of immunoglobulin (Ig) heavy chain gene rearrangements in the five patients studied. Two of the eight patients with complete marker study expressed myeloid-associated antigens on the blasts. A high incidence of CD7 expression (7/17 or 41%) was found in patients with myeloid BC, but none of the patients who had DNA analysis showed rearrangement of T-cell receptor beta chain gene. Chromosomal abnormalities +8, +19, +21, and i(17q) were detected only in the patients with myeloid BC but not in those with lymphoid BC. Combined analysis of the patients in this series and those reported previously has revealed a statistically significant difference in the distribution of bcr breakpoints between myeloid and lymphoid BC: the bcr breakpoints in more than half of the patients with myeloid crisis were mapped to Zone 2 while those in patients with lymphoid crisis occurred most frequently in Zone 3.

Influence of M-BCR breakpoint sites on the duration of chronic phase in 100 patients with chronic myelocytic leukemia

Rearrangements of the bcr (M-BCR) gene were studied in 100 patients with chronic myelocytic leukemia (CML). To determine the significance of a chimeric gene expression in the progression of CML, we analyzed 43 patients for bcr-ABL chimeric mRNA expression. Both DNA and RNA analyses revealed a possible influence of breakpoint sites in the bcr region on the duration of the chronic phase. Patients with the breakpoint located at about the 1-kb region between BamHI and HindIII in bcr exon 3 (region C2) had a significantly shorter chronic phase (31 months) (p = 0.028) than patients in whom the breakpoint was located in other regions. When the bcr locus was divided into 5' and 3' regions as for the BamHI cleavage site located near the 5' region of bcr exon 3, the chronic phase duration in patients with the 5' site (HindIII-BamHI) and 3' site (BamHI-EcoRI site) was 75 and 38 months, respectively. However, the difference was not statistically significant (p = 0.128). These results suggest that only the breakpoint site at C2 on the bcr locus, rather than breakpoint sites in other regions, has an important role in the progression of CML.

The type of BCR/ABL junction does not predict the survival of patients with Ph1-positive chronic myeloid leukaemia

The prognostic value of the location of the breakpoint on chromosome 22 in patients with Ph1+ chronic myeloid leukaemia (CML) is still controversial. We analysed both DNA rearrangement and transcript type in a new continuous series of CML patients. By Southern blotting analysis, we found that, out of 72 patients, 43 had a 5' rearrangement and 29 a 3' one, of the 43 5'-rearranged patients, 35 carried an a2b2 transcript and eight an a2b3 one, while, of the 29 patients rearranged in the 3' part of the M-BCR area, 26 had an a2b3 transcript, one had an a2b2 transcript and two carried both types of transcript. Thus, mRNA studies allow to detect an a2b3 transcript in 17.7% of 5' rearranged patients. However, no correlation was observed between type of transcript and survival, as after DNA studies.

The relationship between the type of bcr-abl hybrid messenger RNA and thrombopoiesis in Philadelphia-positive chronic myelogenous leukemia

Formation of the Philadelphia (Ph1) chromosome, which contains the hybrid bcr-abl gene, is thought to be the initial event in chronic myelogenous leukemia (CML). The positions of the breakpoint within the breakpoint cluster region (bcr) on the bcr-abl gene in 22 chronic-phase cases of Ph1-positive CML were determined using conventional Southern blots, and the splicing pattern were also determined the species of the fused bcr-abl mRNA in 79 CML cases using the polymerase chain-reaction procedure (RT-PCR). The location of the breakpoint within the bcr locus was assigned to one of five zones. Breakpoints in zones 1 and 2 were grouped as 5', and those in zones 3, 4 and 5 as 3'. Nine patients had 5' breakpoints and 13 patients had 3' breakpoints. The platelet counts of 3' patients were significantly higher than those of 5' patients (1395 vs 274 x 10(9)/L; p < 0.03). The megakaryocyte counts from bone marrow histological sections in 3' patients (n = 12) and 5' patients (n = 7) were 63.4/mm2 and 19.5/mm2, with a significant difference at p < 0.006. The mean number of megakaryocyte progenitor cells assayed by in vitro cloning was 128.3/2 x 10(5) bone marrow cells for 3' patients (n = 7) compared with 46.3 for 5' patients (n = 4). Using the RT-PCR technique, the bcr exon 2/abl exon 2 fused mRNA (b2-a2) was detected in 18 patients, the bcr exon 3/abl exon 2 fused mRNA (b3-a2) was detected in 45 patients, and both types of mRNA were detected in 16 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Will molecular biology contribute to refine prognosis and to select treatment? The Molecular Biology Committee. Italian Cooperative Study Group on Chronic Myeloid Leukemia

The possible prognostic value of the position of the breakpoint within the M-BCR in patients with Ph1+ CML is still being debated. We analyzed the DNA rearrangements and the transcript types of 244 patients and tried to correlate the data obtained with prognostic features, defined according to Sokal's risk index, and with chronic phase and/or survival duration. The exact location of the breakpoint, either 5' or 3' to the Hind III restriction site within the M-BCR was identified. Moreover, the exact M-BCR subregion was also identified. As a whole, 150 pts were rearranged in the 5' part and 94 in the 3' part of the M-BCR. No correlation was observed between the site of rearrangement on the one hand and the Sokal's prognostic index and survival, on the other. Transcript analysis was performed in 130 patients; 59 carried an a2b2 and 69 an a2b3 pattern. Two patients carried both transcripts. Of the patients rearranged in the 5' area, according to Southern blotting, 29.2% showed an a2b3 transcript. Therefore, RT-PCR analysis allowed a better definition of the breakpoint. However, also the type of transcript did not show any correlation either with risk categories or survival. No difference in response to therapy, either chemotherapy or alpha interferon, was observed between 5' and 3' rearranged patients.

The relationship between the location of the breakpoint within the M-bcr and clinical parameters

The Philadelphia chromosome (t9;22)(q34;q11) is a characteristic abnormality in chronic myeloid leukemia. In greater than 95% of the cases, the breakpoint occurs with the M-bcr region of the BCR gene on chromosome 22. Several studies have attempted to correlate the location of the breakpoint within the M-bcr with a clinical parameter. The majority of studies have examined the relationship between the site of breakpoint and the median chronic phase duration (CPD). Some studies have reported a correlation, with 5' breakpoint patients who have a longer median CPD than patients with a 3' breakpoint. However, other groups have reported that no correlation exists. Furthermore, data from some of the latter groups have suggested that a correlation may exist with the lineage of blast crisis which developed and 3' breakpoint patients had a higher than expected number of lymphoid blast crisis. A correlation between high platelet counts at diagnosis and patients with a 3' breakpoint or those who expressed a b3-a2 BCR-ABL mRNA has also been described. No consistent conclusion from any of these studies can be drawn. This may due, in part, to some degree of patient and sample selection, although environmental, genetic or life-style factors may also contribute.

Confirmation and improvement of Sokal's prognostic classification of Ph+ chronic myeloid leukemia: the value of early evaluation of the course of the disease. The Italian Cooperative Study Group on Chronic Myeloid Leukemia

A simple prognostic classification of Ph+ chronic myeloid leukemia (CML) was proposed in 1984 by an international study Group and is now widely used for clinical purposes. That study was retrospective, and was based on disease features at diagnosis. To test prospectively and to check the value of the classification, and to investigate if additional information on the early course of leukemia can help in refining the prognosis, 505 Ph+, nonblastic and nontransplanted patients first registered between 1984 and 1986 were followed up to June 1990. It was found that the prognostic formulation predicted survival in that series exactly the same way as in the original series (median survival: greater than 60 months for low-risk patients, 46 months for intermediate-risk patients, and 32 months for high-risk ones). It was also found that several objective or subjective assessments of disease course during the first 8 months after diagnosis were significantly related to survival length within any risk group. This study provides full confirmation of Sokal's international prognostic classification, and shows that the definition of prognosis can be improved some months after diagnosis by taking into account the course of the disease and the response to therapy. These conclusions apply to patients receiving conventional treatment. The course of Ph+ chronic myeloid leukemia (CML) is rigidly programmed to progress to an acute phase, which is called blastic metamorphosis (BM) and which can develop either suddenly (blastic crisis) or by a slow progression (accelerated phase). In all recent series, 2-year survival ranged between 65% and 80%, median survival was slightly shorter than 4 years, and the proportion of patients who were still alive after 10 years was less than 10%. However, a number of prognostic variables were identified and a prognostic formulation that was elaborated by an international study was shown to provide a reliable estimate of survival length and is currently used for that purpose. The value of that formulation, and the formulation itself, require periodical controls and revisions. For that purpose, the Italian Cooperative Study Group on CML registered and followed up all CML patients who were first seen between 1984 and 1986. A very preliminary analysis of that cohort of patients has already been performed, but it was limited to the first 2 years after diagnosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Karyotype evolution of Ph positive chronic myelogenous leukemia patients relapsed in advanced phases of the disease after allogeneic bone marrow transplantation

Sixty-eight patients affected by Philadelphia chromosome (Ph) positive chronic myelogenous leukemia (CML) underwent allogeneic bone marrow transplantation (BMT) and were successfully studied from a cytogenetic point of view, before and after the BMT. Nineteen had evidence of cytogenetic and clinical relapse. Cytogenetic analyses of 14 patients who, after the relapse, showed progression to the accelerated or blastic phase of the disease, are presented. Five of these cases had only the Ph chromosome without karyotype evolution; in one case Ph duplication without other anomalies was detected, while in the remaining eight cases cytogenetic analysis showed apparently random clonal structural abnormalities (translocations, inversions, deletions, and marker formations). Therefore, the classical "non-random" abnormalities (+8, i(17q), +Ph, +19, +21) were not as common as in conventionally treated Ph+ CML. From our data, karyotype evolution during advanced phases in Ph+ CML patients after BMT differs from the evolution seen in conventionally treated patients, by the presence of numerous structural unusual abnormalities, possibly related to radiochemotherapy conditioning to BMT. Therefore, BMT treatment is not always able to eradicate the Ph+ clone but can reduce the incidence of the formation and/or expansion of Ph+ clones with additional non-random abnormalities.

Sequence-specific DNA-binding proteins within the Mbcr on the Ph1 chromosome

The Philadelphia1 (Ph1) chromosome results from a reciprocal translocation between chromosome 9 and chromosome 22, which fuses a portion of the ABL oncogene to the BCR gene, forming the BCR/ABL fusion gene. This produces a fusion protein with a greatly increased protein tyrosine kinase activity in comparison to that of the normal ABL protein. The BCR/ABL gene is transcribed from the promoter of the normal BCR gene, but little is known about the regulation of its expression. In this study, we asked whether there are sequence-specific DNA-binding proteins (DBP) that bind to the breakpoint cluster region (bcr, or Mbcr) within the BCR gene. Sequence-specific DBP located within the Mbcr could have a transcription-regulating effect, and they could participate in the recombination that generates BCR/ABL. Our data show that there are sequence-specific DBP that bind within the Mbcr.

The molecular genetic analysis of gene rearrangements in acute lymphoblastic leukaemia

In ALL the majority of cases possess clonal rearrangements of the Ig or TCR gene loci. Detection of these clonal markers by Southern blot analysis over a disease course has provided information on the fate and origin of leukaemic clones during treatment. Detection of these gene rearrangements has been used to detect residual disease during treatment. More recently, methods have been developed for the detection of Ig and TCR gene rearrangements using the polymerase chain reaction (PCR). This amplification technique allows for the rapid detection of gene rearrangements with a greater sensitivity than more conventional methods. The full impact and usefulness of this technique in residual disease detection has yet to be determined. The presence of the Philadelphia chromosome t(9;22) in ALL is associated with poor prognosis. Its detection by Southern blot is technically complicated due to the heterogeneity of chromosome breakpoints involved. The development of PCR-based methods for the detection of the bcr/abl mRNA associated with the Philadelphia chromosome has improved our understanding of the significance and incidence of this disease marker in ALL, emphasizing the importance of establishing Philadelphia status on all patients at diagnosis. Although longitudinal studies in CML have shown the presence of bcr/abl mRNA to be associated with residual disease, and its absence associated with long-term remission, these studies have yet to be reported for ALL. The usefulness of detection of residual disease using bcr/abl has yet to be determined.