Chronic granulocytic leukemia: correlation of blastic transformation type with karyotypic evolution

Double Philadelphia masquerading as chromosome 20q deletion - a new recurrent abnormality in chronic myeloid leukaemia blast crisis

The most common abnormality of chromosome 20 in haematological malignancy is deletion of the long arm [del(20q)]. These interstitial deletions are variable in size and are seen in both premalignant haematological conditions and acute myeloid neoplasia. A commonly deleted region (CDR), mapped within the 20q11.2/q13.1 segment with an estimated size of 1.7 Mbp, is considered to present a primary genetic lesion marking a gene(s), the loss of which is responsible for the pathogenesis of these haematological disorders. While a small number of recurrent translocations involving chromosome 20 have also been reported, no recurrent aberration of this chromosome has been associated with myeloid disease progression. We present nine cases of Philadelphia (Ph)-positive chronic myeloid leukaemia (CML) in which deletions of chromosome 20 were also detected by conventional karyotyping. In six cases, fluorescent in situ hybridization (FISH) mapping confirmed a del(20q) which corresponded to the myeloid CDR. In the remaining three cases however, the presumed del(20q) marker was shown to be the result of an unbalanced translocation between band 20p11 and a second copy of the Ph chromosome. This new abnormality, termed dic(20;Ph) for short, was identical to a del(20)q by G-banding, and combined duplication of the breakpoint cluster region and Abelson murine leukaemia viral oncogene homologue (BCR-ABL) fusion with loss of the 20p11-pter segment. In all three cases, the dic(20;Ph) was associated with disease progression and therefore represents a new recurrent abnormality in CML blast crisis.

Chronic myelogenous leukemia as a paradigm of early cancer and possible curative strategies

The chronological history of the important discoveries leading to our present understanding of the essential clinical, biological, biochemical, and molecular features of chronic myelogenous leukemia (CML) are first reviewed, focusing in particular on abnormalities that are responsible for the massive myeloid expansion. CML is an excellent target for the development of selective treatment because of its highly consistent genetic abnormality and qualitatively different fusion gene product, p210(bcr-abl). It is likely that the multiple signaling pathways dysregulated by p210(bcr-abl) are sufficient to explain all the initial manifestations of the chronic phase of the disease, although understanding of the circuitry is still very incomplete. Evidence is presented that the signaling pathways that are constitutively activated in CML stem cells and primitive progenitors cooperate with cytokines to increase the proportion of stem cells that are activated and thereby increase recruitment into the committed progenitor cell pool, and that this increased activation is probably the primary cause of the massive myeloid expansion in CML. The cooperative interactions between Bcr-Abl and cytokine-activated pathways interfere with the synergistic interactions between multiple cytokines that are normally required for the activation of stem cells, while at the same time causing numerous subtle biochemical and functional abnormalities in the later progenitors and precursor cells. The committed CML progenitors have discordant maturation and reduced proliferative capacity compared to normal committed progenitors, and like them, are destined to die after a limited number of divisions. Thus, the primary goal of any curative strategy must be to eliminate all Philadelphia positive (Ph+) primitive cells that are capable of symmetric division and thereby able to expand the Ph+ stem cell pool and recreate the disease. Several highly potent and moderately selective inhibitors of Bcr-Abl kinase have recently been discovered that are capable of killing the majority of actively proliferating early CML progenitors with minimal effects on normal progenitors. However, like their normal counterparts, most of the CML primitive stem cells are quiescent at any given time and are relatively invulnerable to the Bcr-Abl kinase inhibitors as well as other drugs. We propose that survival of dormant Ph+ stem cells may be the most important reason for the inability to cure the disease during initial treatment, while resistance to the inhibitors and other drugs becomes increasingly important later. An outline of a possible curative strategy is presented that attempts to take advantage of the subtle differences in the proliferative behavior of normal and Ph+ stem cells and the newly discovered selective inhibitors of Bcr-Abl. Leukemia (2003) 17, 1211-1262. doi:10.1038/sj.leu.2402912

BCR/ABL amplification in chronic myelocytic leukemia blast crisis following imatinib mesylate administration

The onset of accelerated phase or blast crisis of chronic myelocytic leukemia (CML) is usually associated with the acquisition of new chromosome abnormalities in addition to the t(9;22)(q34;q11) that is characteristic of the chronic phase CML. We describe the cytogenetic and molecular genetic findings in two cases of myelocytic blast crisis of CML, one occurring 6 months after commencing treatment with the ABL-specific tyrosine kinase inhibitor imatinib mesylate (STI571, Glivec, or Gleevec) and the second treated with imatinib mesylate for established blast crisis. In both cases, multiple secondary cytogenetic abnormalities were observed at transformation, with homogeneously staining regions that were shown to contain BCR/ABL amplification by fluorescence in situ hybridization appearing after imatinib mesylate administration. BCR/ABL amplification is emerging as an important mechanism of acquired resistance to imatinib mesylate.

Factors affecting duration of survival after onset of blastic transformation of chronic myeloid leukemia

We analyzed factors having an impact on response to treatment and survival in 78 consecutive patients with chronic myeloid leukemia (CML) in blastic transformation (BT) referred to the Hammersmith Hospital from January 1995 to December 2000. BT was defined as the presence of at least 30% blasts in blood or marrow or extramedullary blastic deposits. Immunophenotyping of blasts showed 57 myeloid, 19 lymphoid, and 2 biphenotypic. The median age of the patients was 39.1 years (range, 11.3-73.4 years), with 55 males and 23 females. The median survival for all patients after onset of BT was 8.2 months (95% CI, 6.4-10). Patients in lymphoid BT survived longer than those in myeloid BT (median, 11.2 months versus 6.9 months, P =.052). Initial treatment varied; 41 patients received cytotoxic drugs, 8 underwent allogeneic or autologous transplantation procedures, 21 received STI571 (imatinib mesylate, Gleevec), 1 received radiotherapy, and 7 received no therapy. Of the 25 (32%) patients who achieved a "second chronic phase" with first therapy, 6 of 21 (29%) were treated with STI571 and 19 of 50 (38%) were treated with chemotherapy, transplantation, or radiotherapy. Patients who achieved a second chronic phase survived longer than those who did not (median time from onset of BT 12.0 months versus 6.3 months, P =.0004). In multivariate analysis the finding of more than 50% blast cells in the blood and the presence of cytogenetic progression were independent adverse prognostic variables for survival. We conclude that survival after onset of BT has improved in recent years but is still unsatisfactory. We speculate that the combined use of STI571 with cytotoxic drugs may offer additional benefit.

Cytogenetics of chronic myeloid leukaemia

The standard Philadelphia (Ph) translocation t(9;22), its variants and a proportion of Ph-negative cases are positive for the BCR-ABL fusion gene, as determined by molecular analysis. Extensive deletions of chromosome 9 and 22 derived sequences around the translocation breakpoints on the derivative 9 are seen in 10-30% of patients at diagnosis and may confer a worse prognosis. Additional cytogenetic changes can occur in the few months before or during disease progression and are often specific for blast morphology; however, the molecular basis of the most common additional cytogenetic abnormalities is largely unknown. Cytogenetics is important for monitoring patient response to treatment but is increasingly being replaced by the more sensitive and less invasive techniques of RT-PCR and FISH.

Cytogenetic divergence of the same blastic clone in transformed chronic granulocytic leukemia: no effect on morphologic and immunologic features

A 19-year-old man with Ph-positive chronic granulocytic leukemia developed lymphoblastic transformation. Cytogenetic evolution was observed, with an abnormal clone showing i(17q) together with the t(9;22). Chronic phase of the chronic granulocytic leukemia were re-established with systemic chemotherapy, which also led to disappearance of the clone with i(17q). However, the acute lymphoblastic leukemia relapsed after 6 weeks, with the emergence of a phenotypically and genetically identical but cytogenetically distinctive clone. Our findings suggest that cytogenetic evolution in transformed chronic granulocytic leukemia reflects only the instability of the blastic clones, and may not determine its phenotypic differentiation.

Cytogenetics of chronic myelogenous leukaemia

The Philadelphia (Ph) chromosome is present in the leukaemic cells of most patients with chronic myelogenous leukaemia. Variant translocations occur in 10% of patients but breakpoints on chromosomes 9 and 22 remain the same, so prognosis of these patients is unchanged. Clonal evolution is infrequent in chronic phase and its significance depends on the specific chromosome involved, the number of metaphases affected and the timing in the chronic phase. The majority of patients in blastic phase demonstrate clonal evolution; three specific abnormalities (+Ph, +8 and isochromosome 17q) are present in 70% of patients. Loss of the Ph chromosome on therapy is associated with prolonged survival. For monitoring these events conventional G-band cytogenetics (CG) is essential at presentation to characterize the Disease cytogenetically, while fluorescence in situ hybridization (FISH) on hypermetaphase preparations (hypermetaphase FISH (HMF)) is important for establishing the specific frequency of Ph+ cells. During treatment FISH on interphase cells (I-FISH) can monitor the level of Ph+ cells in circulation, while CG may be used to identify any suspected clonal evolution. Where I-FISH is negative, HMF is essential to evaluate minimal residual disease.

Primary vs. secondary neoplasia-associated chromosomal abnormalities--balanced rearrangements vs. genomic imbalances?

Two quite distinct neoplasia-associated karyotypic patterns are emerging. One is characterized by simple and disease-specific abnormalities, and the other is characterized by multiple and nonspecific aberrations. The former pattern is typical of most leukemias and lymphomas and of some mesenchymal tumors, but it is rare in epithelial neoplasms. The latter pattern is found in most epithelial tumor types, in several mesenchymal neoplasms, but in only a few hematologic malignancies. Primary chromosome aberrations, which are believed to be essential in establishing the neoplasm, and secondary changes, which are considered to be important in tumor progression, may be distinguished in the tumors characterized by simple and disease-specific abnormalities. Here, we propose that these aberrations are genetically and hence, most likely, functionally distinct. Primary abnormalities lead to specific gene rearrangements, whereas secondary chromosomal changes result in large-scale genomic imbalances. According to this hypothesis, there are no unbalanced primary aberrations, only secondary imbalances masquerading as primary. This proposition has a number of conceptual ramifications. First, the genetic mechanisms underlying tumor initiation and progression would seem to be totally different. Second, the elucidation of the molecular consequences of the secondary aberrations will be an arduous task, even if one were to adhere to the view that cytogenetically identified genomic imbalances may be reduced to simple gains or losses of single oncogenes or tumor suppressor genes. Third, the cytogenetic diagnosis of neoplasms will have to take into account that an unbalanced "primary" abnormality is secondary to a submicroscopic, truly primary change of major diagnostic and prognostic importance.

Karyotypic findings as an independent prognostic marker in chronic myeloid leukaemia blast crisis

Fifty-three patients with Ph positive chronic myeloid leukaemia in blastic phase were studied. Additional abnormalities were found in 29 (55%) patients and were more common in myeloid (64%) than lymphoid (45%) blast crisis. The most frequent were +Ph (32%), +8 (28%), +19 (19%), +20 (9%) and +21 (9%). i(17q) (9%) was associated with thrombocytopenia (5/5) and basophilia (2/5). The incidence of additional abnormalities was higher in patients treated with busulphan (70%) than hydroxyurea (44%). No significant differences were noted in the mean values of the clinical and haematological findings recorded at blast crisis between patients with only Ph positive (PP) cells and those with additional abnormalities (AP + AA). Univariate analysis identified karyotypic findings as an independent prognostic marker indicating its significance in assessing the response to therapy and survival after the onset of transformation.

Trisomy 19 as the sole chromosomal anomaly in hematologic neoplasms

Trisomy 19 was found as the sole chromosomal aberration in three hematologic malignancies: one chronic myelomonocytic leukemia and two cases of of immunophenotypically immature acute myeloid leukemia (AML). A compilation of previously published hematologic neoplasms with +19 as the only change reveals that this anomaly is strongly associated with myeloid malignancies; 25 of 31 cases have been myelodysplastic syndromes (MDS) or AML. Eight of the 11 MDS cases have been either refractory anemia (RA) or RA with excess of blasts, and four of the 14 AML cases have had preleukemic myelodysplastic cases phase, with the +19 accruing during the time of leukemic transformation. The AML cases have, in general, been either or early maturation arrest, i.e. undifferentiated or AML-M1/M2, or of myelomonocytic-monoblastic origin, i.e., AML-M4/M5. None of the MDS or AML cases with +19 had had a previous history of radio- or chemotherapy. We conclude that trisomy 19, as the sole anomaly, is a characteristic abnormality in de novo myeloid malignancies. No clinical features seem to characterize patients with +19 AML and MDS and the prognostic impact of the aberration remains to be elucidated.

Chromosome abnormalities in non-small cell lung cancer pleural effusions: cytogenetic indicators of disease subgroups

A cytogenetic study of pleural effusions (PE) containing metastatic or invasive tumor cells from 11 patients with non-small cell lung cancer (NSCLC) (3 squamous cell carcinomas [SQC] and 8 adenocarcinomas [ADC] including 1 giant cell variant) was performed to identify non-random chromosome abnormalities. Numerical abnormalities seen in > or = 30% of cases included gain of chromosomes 7 and 20, and loss of chromosomes 4, 9, 10, 13, 15, 16, 18, 19, 21, and 22. The most frequent structural abnormality involved rearrangement in 1p with breakpoints clustering at 1p10-p13. Other recurrent breakpoint regions, seen in > or = 30% of cases, occurred in chromosome region 3p10-p21, 3q11-q25, 6p11-p25, 6q13-q23, 7q11-q36, 9q32-q34, 11p11-p13, 11q13-q24, 13p/14p and/or 15p, 17p and 19p, with, in particular, apparent loss of 6q21-q27, 3p21-p26, 7q21-q22, 9p22-p24 (shortest regions of common overlap) and 17p. There was also recurrent gain of 1q23-q44, 8q13-q24, and 11q13-q23. These abnormalities were not restricted to a particular histological subtype, with the exception of +8 and a breakpoint in 9q32-q34, which were seen only in ADC. The 9q32-q34 breakpoint observed in 4 ADC PE (including 1 giant cell variant) represents a new observation in NSCLC. These findings, when compared to those reported for primary NSCLC indicate cytogenetic differences between the two which may be associated with pleural invasion of NSCLC.

Karyotype at relapse following allogeneic bone marrow transplantation for chronic myelogenous leukemia

Eighty-four patients underwent allogeneic or syngeneic bone marrow transplantation as therapy for chronic myelogenous leukemia (CML) during a 5-year period at The Johns Hopkins Oncology Center. We describe the karyotype at relapse in 19 patients who were Ph chromosome positive (Ph+) at diagnosis. Eighty-four percent of patients demonstrated clonal and/or nonclonal chromosome abnormalities in addition to the t(9;22)(q34;q11) at first detection of relapse or later during relapse. These abnormalities included: Ph plus additional clonal abnormalities (three patients), Ph plus nonclonal abnormalities (five patients), Ph plus additional clonal and nonclonal abnormalities (eight patients). Three patients had only the original Ph+ clone. The additional chromosome abnormalities were primarily structural, and entirely different from those most frequently observed during karyotypic evolution in conventionally treated CML. Chromosome 1 was most frequently involved, with 1q32 being the location of three clonal and two nonclonal abnormalities. Other sites included 6p21-22 (the site of two clonal abnormalities), 7p21-22, and 10q21 (the site of two clonal and one nonclonal abnormality each). Chromosomes 5 and 7q, regions of frequent involvement in acute nonlymphocytic leukemia that follows chemotherapy for other malignancies, were infrequently involved. The clinical significance of these additional abnormalities remains undetermined at this time.

Ph-positive chronic myeloid leukemia with t(8;21)(q22;q22) in blastic crisis

A patient diagnosed with chronic myeloid leukemia was studied periodically during his illness. The result showed the presence of a Philadelphia (Ph) chromosome by a 9;22 translocation as a single abnormality to the time of blastic crisis. At that time, the chromosome studies showed a clonal evolution. Furthermore, a second derivated line was added to the Ph line. This new anomaly consisted of a 8;21 translocation, considered as specific of M2 type acute nonlymphoblastic leukemia of French-American-British classification.

T-lymphoid blast crisis in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is considered to be a pleuripotential stem cell disorder with the capacity to differentiate into myeloid, erythroid, megakaryocytic, and lymphoid cell lines. Consequently, blast crisis (BC) involving each of the above lineages has been well described. Among lymphoblastic crises, differentiation frequently occurs along B-cell lineage. We report four patients of CML who terminated in T-cell extramedullary BC in lymph nodes after a variable duration of chronic phase. The T-lineage was established by characteristic cytochemical staining and reactivity with a panel of anti-T-cell monoclonal antibodies. All four cases were Philadelphia (Ph) chromosome positive and demonstrated the Ph chromosome and associated anomalies (extra Ph, +19) in the lymph nodes. Our data adds to the growing evidence that CML is a disorder of the common stem cell from which T, B, and myeloid precursors originate.

Cytogenetic peculiarities in chronic myelogenous leukemia

Cytogenetic investigations were performed in 185 patients with chronic myelogenous leukemia (CML) at all stages of the disease; 166 patients were Ph positive-159 (95.8%) of these showing the standard Ph translocation, and 7 (4.2%) variant translocations-17 patients were Ph negative. In 2 patients the cytogenetic analysis was unsuccessful. Additional aberrations were found in 40 (24.1%) of the Ph-positive patients. Nine (52.9%) of the Ph-negative patients showed chromosome anomalies. Besides the well known nonrandom abnormalities (-7, +8, i(17q), +19, +Ph) we found a high frequency of clones with rare or not yet described structural rearrangements--in 14 cases (34.2%) of the Ph-positive patients and in 2 cases (20%) of the Ph-negative patients with other chromosome abnormalities. The clinical significance of these findings is discussed.

Prognostic significance of secondary cytogenetic changes and nonspecific cross-reacting antigen (NCA) in patients with Ph-positive chronic myeloid leukemia

Cytogenetic analyses were carried out on peripheral blood and bone marrow cells of 31 chronic myeloid leukemia (CML) patients who presented with blastic, accelerated, or chronic phases. The percentage of cytoplasmic nonspecific cross-reacting antigen (cNCA, a marker of myelocytic differentiation)-containing cells was determined in the same blood or bone marrow samples. The patients were divided in two groups according to cytogenetic results: those with aberrations in addition to the Philadelphia chromosome (Ph1) and those with Ph1 only. Among the additional aberrations such changes, not typical of CML, were found: del(2)(p21), t(6;11)(q25;q23), and t(12;?)(p13;?). The survival time and the percentage of cNCA-positive cells of patients in blastic and accelerated phases were compared between the above-mentioned two groups of patients using the Student t test and the Kaplan-Meier estimator. The percentage of cNCA-positive cells was significantly lower and the survival time significantly shorter in the group of patients with additional aberrations. The probability of survival according to the Kaplan-Meier estimator was also lower for this group. These data suggest that the immunologically determined lower degree of maturity, that characterized cells bearing additional aberrations, coincides with and/or results in more rapid progression of the disease.

Seven variants including four new Philadelphia translocations

This paper reports on seven atypical Philadelphia chromosome translocations in chronic myelocytic leukemia. Three of them, a t(16;22), t(17;22), and t(9;14;22) have already been observed before, while the t(X;9;11;22), t(X;22), t(3;22) and t(3;4;9;22) are newly reported.

Characterisation of blast cells during blastic phase of chronic myeloid leukaemia by immunophenotyping--experience in 60 patients

The blast cell population of 60 patients with chronic myeloid leukaemia in blast crisis (CML-BC) were analyzed with a panel of monoclonal antibodies to determine the cell surface antigen phenotypes. In addition, cytochemical stains periodic acid Schiff (PAS), myeloperoxidase (MP), Sudan black B (SBB) and terminal deoxynucleotidyl transferase (TdT) were also utilized for subtyping. Nineteen cases (31.6%) expressed lymphoid phenotypes characteristic of common ALL cells and one case with extramedullary lymph node crisis expressed T-cell surface phenotypes. Thirty cases (50%) expressed solely myelomonocytic surface antigens with significant TdT activity in three. Cytochemical stains contributed to recognize only 57% of these myeloid blasts. Seven cases (11.7%) were with a mixture of heterogenous group of cells expressing phenotypic characteristics for various haemopoietic cells of different lineage--five of them from the cells of non-lymphoid series (myelomono-erythromegakaryocytic series) and the other two with cells from both lymphoid and myeloid series. Additionally, in two cases (3.3%), the precursor cells reacted only with the erythroid monoclonals. Finally, in one case, the blast cells remained unclassified due to nonreactivity with any of the monoclonals used but expressed significant TdT positivity. The response to uniform vincristine and prednisolone (V + P) therapy has shown that lymphoid blast crisis cases were highly responsive in contrast to the cases with non-lymphoid blast crisis (complete remission rate 86 vs 21.4%). The results confirm the evidence of multilineage blast crisis involving either single or mixed haemopoietic differentiation pathway and the utility of having phenotypic characterisation for designing protocols for chemotherapy in the CML patients at the time of blast crisis.

Silver bands in chronic granulocytic leukemia. II. The Philadelphia chromosome

To test if rRNA gene activity in the Philadelphia (Ph) chromosome nucleolar organizing regions (NOR) differs from other NOR we scored silver banding patterns in leukemic cells of 32 patients (one patient was sampled twice) in the chronic phase of chronic granulocytic leukemia. The average number of bands per NOR in banded cells of these patients was 0.40 +/- 0.06 for the Ph NOR, not significantly different from the 0.41 +/- 0.02 per D chromosome NOR or the 0.41 +/- 0.04 per G. Across the 33 cases, the number of different Ph NOR banded in at least one cell (23 of 33, 70%) was also closely similar to the cumulative maximum number of chromosome D NOR banded per cell (137 of 198 banded, 69%) and G NOR banded (67 of 99, 67%). We conclude that the activity of rRNA genes in Ph NOR is closely similar to that of the other nine NOR in each CGL cell. In situ hybridization of 3H-labeled complementary rRNA to NOR of two patients revealed that the mean number of Ph NOR grains fell within the range of the other NOR. Also, grain distributions across the NOR of leukemic cells closely matched those of stimulated lymphocytes. Thus, a limited sampling has shown no evidence for consistent differences or changes in the rRNA gene number of Ph NOR.

Genomic diversity of Philadelphia-positive chronic myelogenous leukemia

The incidence of breakpoints in CML patients with variant translocations was investigated. There was no relationship between the length of various chromosomes with breakpoint frequency. However, a significantly higher (p less than 0.05) incidence of breaks were seen on the long arms as compared to the short arms due mainly to the involvement of 9q and 22q in these translocations. Chromosome 17 showed a significantly (p less than 0.005) higher involvement in these translocations, however only when 9q34-qter was not cytogenetically involved. A total of 683 breaks were found in 225 cases. 362 of these were located at c-abl and c-sis, while 110 were at other oncogenetic sites. The prognostic and hematologic features of patients with variant translocations are not significantly different from those of CML cases with the typical 9q;22q translocation. Some of these complex translocation, where the breakpoints are correlated with oncogenetic sites, are further discussed in molecular terms.

Complex chromosomal abnormalities in a patient with lymphoid blast crisis of chronic myelogenous leukemia

A 46-year-old Chinese man underwent lymphoid blast crisis (Ia+, CALLA+, TdT+) after 5 years of chronic phase, Philadelphia-chromosome positive chronic myelogenous leukemia. Chromosome analysis revealed a hyperdiploid karyotype, including two Philadelphia chromosomes--55,XY,t(9;22) (q34;q11), +2, +5, +5, +6, +10, +18, +19, +21, +del(22)(qll----qter)--in the majority of the leukemic blasts. The constellation of a lymphoid blast crisis and complex chromosomal abnormalities usually associated with myeloid blast crisis as well as the clinical data are discussed.

Chronic granulocytic leukemia: the devastating consequences of genetic instability

Recent advances in the pathogenesis and treatment of chronic granulocytic leukemia (CGL) are reviewed. Three major phases of CGL are recognizable: the presymptomatic phase, the chronic phase, and the metamorphosis. The molecular dissection of the Philadelphia chromosome has revealed that this translocation activates the c-abl oncogene by fusion with another gene called bcr whose function is as yet unknown. Although almost all patients with CGL still succumb within 10 years of diagnosis, alpha-interferon and allogeneic bone marrow transplantation represent promising newer therapeutic developments. In particular, marrow transplantation appears to have curative potential in CGL.