Chromosomal characteristics of chronic and blastic phases of Ph-positive chronic myeloid leukemia

Prognostic significance of isochromosome 17q in hematologic malignancies

Isochromosome 17q [i(17q)] with its two identical long arms is formed by duplication of the q arm and loss of the short p arm. The breakpoint in chromosome 17 that allows the formation of this isochromosome is located at 17p11.2, and the ~240 kb region with its large, palindromic, low-copy repeat sequences are present here. The region is highly unstable and susceptible to a variety of genomic alterations which may be induced by or without toxic agents. One molecular consequence of i(17q) development is the obligatory loss of a single TP53 allele of the tumor suppressor P53 protein located at 17p13.1. Isochromosome 17q is involved in cancer development and progression. It occurs in combination with other chromosomal defects (complex cytogenetics), and rarely as a single mutation. The i(17q) rearrangement has been described as the most common chromosomal aberration in primitive neuroectodermal tumors and medulloblastomas. This isochromosome is also detected in different hematological disorders. In this article, we analyze literature data on the presence of i(17q) in proliferative disorders of the hematopoietic system in the context of its role as a prognostic factor of disease progression. The case reports are added to support the presented data. Currently, there are no indications for the use of specific treatment regimens in the subjects with a presence of the isochromosome 17q. Thus, it is of importance to continue studies on the prognostic role of this abnormality and even single cases should be reported as they may be used for further statistical analyses or meta-analyses.

High-risk additional chromosomal abnormalities at low blast counts herald death by CML

Blast crisis is one of the remaining challenges in chronic myeloid leukemia (CML). Whether additional chromosomal abnormalities (ACAs) enable an earlier recognition of imminent blastic proliferation and a timelier change of treatment is unknown. One thousand five hundred and ten imatinib-treated patients with Philadelphia-chromosome-positive (Ph+) CML randomized in CML-study IV were analyzed for ACA/Ph+ and blast increase. By impact on survival, ACAs were grouped into high risk (+8, +Ph, i(17q), +17, +19, +21, 3q26.2, 11q23, -7/7q abnormalities; complex) and low risk (all other). The presence of high- and low-risk ACAs was linked to six cohorts with different blast levels (1%, 5%, 10%, 15%, 20%, and 30%) in a Cox model. One hundred and twenty-three patients displayed ACA/Ph+ (8.1%), 91 were high risk. At low blast levels (1-15%), high-risk ACA showed an increased hazard to die compared to no ACA (ratios: 3.65 in blood; 6.12 in marrow) in contrast to low-risk ACA. No effect was observed at blast levels of 20-30%. Sixty-three patients with high-risk ACA (69%) died (n = 37) or were alive after progression or progression-related transplantation (n = 26). High-risk ACA at low blast counts identify end-phase CML earlier than current diagnostic systems. Mortality was lower with earlier treatment. Cytogenetic monitoring is indicated when signs of progression surface or response to therapy is unsatisfactory.

Guide to interpreting disease responses in chronic myeloid leukemia

With the introduction of tyrosine kinase inhibitor (TKI) therapy for chronic myeloid leukemia, the course of the disease has been altered from an acute, rapidly progressive terminal disorder to a serious condition with high remission rates when patients are compliant with long-term treatment. The goal of therapy is to prevent transformation to the accelerated or blast crisis phases, which are associated with poor survival. Knowledge of the appropriate monitoring tests and treatment milestones, as well as the ability to interpret responses, allows advanced practitioners (APs) to effectively communicate key aspects of management to their patients. Monitoring patient responses to TKIs and identifying suboptimal responses early on offer APs the opportunity to reevaluate and adjust therapeutic treatment options. One of the causes of treatment failure is noncompliance; thus, educating patients on the importance of adhering to treatment and identifying reasons for noncompliance are of major importance. Because intolerance to TKIs may lead to discontinuation, frequent monitoring of side effects and response to treatment, open communication, patient education, and careful management are all essential in helping patients remain compliant with therapy. This review discusses the AP's role in helping patients achieve their best response to TKI therapy and optimize their long-term outcomes.

Genomic instability in chronic myeloid leukemia: targets for therapy?

Philadelphia positive (Ph+) chronic myeloid leukemia (CML) is characterized by the occurrence of nonrandom genetic and cytogenetic abnormalities during disease progression. Many of these abnormalities are markers for genes which, when altered, can drive the blastic transformation process. Thus, such genetic alterations may be manifestations of an underlying genomic instability resulting from a compromised DNA damage and repair response, leading to advanced stages of CML and resistance to therapy. This article examines the molecular pathways that may lead to genomic instability in CML and the potential of these pathway constituents to be therapeutic targets.

Blast crisis of Ph-positive chronic myeloid leukemia with isochromosome 17q: report of 12 cases and review of the literature

Isochromosome 17q [i(17q)] is frequently observed in the blast crisis (BC) of chronic myelogenous leukemia (CML). It has been suggested that this chromosome abnormality is associated with special hematological characteristics of the BC, but the information on this subject is scarce. The clinical, hematological and cytogenetic features of patients with i(17q) were analyzed in a series of 121 patients with BC of Ph-positive CML. Twelve patients (10%) displayed an i(17q), representing the third commonest cytogenetic abnormality, after trisomy 8 and Ph chromosome duplication. In seven of the 12 patients the BC was preceded by an accelerated phase, and 10 had more than 10% blood basophils at BC diagnosis. The blast cells had a myeloid phenotype in the 12 patients. Five patients exhibited cytogenetic abnormalities in addition to i(17q), with trisomy 8 and duplication of the Ph chromosome being the alterations most frequently observed. Median survival of patients with i(17q) was 22 weeks, which was not significantly different from the survival of patients with myeloid BC in the overall series. These results are similar to the findings in 181 patients with i(17q) from 12 series of the literature, and confirm the special hematologic profile of BC of CML with this cytogenetic abnormality.

Fluorescence in situ hybridization (FISH) on peripheral blood smears for monitoring Philadelphia chromosome-positive chronic myeloid leukemia (CML) during interferon treatment: a new strategy for remission assessment

Interferon-alpha (IFN-alpha) alone or in combination with cytostatic drugs can induce major and durable cytogenetic responses in about 20 to 25% of chronic myeloid leukemia (CML) patients. Since these patients have a significant survival benefit, more frequent follow-up investigations have become clinically important but require bone marrow (BM) aspirates. The aim of our study was to evaluate interphase fluorescence in situ hybridization (IPF) on peripheral blood (PB) smears as a rapid and reliable method to quantify Ph-positive myeloid cells. IPF analysis was performed on 49 PB samples from 36 patients in the chronic phase of CML and at different stages of cytogenetic remission. IPF results of 30 PB samples were compared with those from BM aspirates simultaneously obtained from the same patients to evaluate the correlation of Ph-positive cells. Further, the hypermetaphase FISH (HMF) technique was performed on cultured BM preparations of 31 patients for comparison with IPF results on PB. An excellent correlation was observed between the IPF results obtained on PB and BM samples (r = 0.98, y = x - 0.6, p < 0.0001). The mean difference between HMF from BM, on the one hand, and IPF from PB, on the other hand, was 3.2% (SD = +/- 8.4%). Seventy percent of samples were identically classified in one of the four subgroups of cytogenetic response. Thirty percent were classified in neighbouring response groups. We conclude that FISH performed on PB is a rapid and reliable method for assessing the cytogenetic response of CML patients on IFN-alpha based therapies, allowing more frequent and less invasive follow-up investigations although it is not able entirely to replace routine analysis of BM.

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.

Clastogenic and aneuploidizing effects of antiblastic busulphan revealed by kinetochore immunofluorescence in CHO cells

We utilized, in CHO cells, the cytoplasm preservation technique to evaluate the micronucleus frequency at different busulphan concentrations, and the indirect immunofluorescence technique, using sera obtained from patients with scleroderma (CREST variant), to analyze if busulphan-induced micronuclei have kinetochores. Results show that this alkylating agent is capable of causing a significant increase of micronuclei in vitro, a great part (40%) of them having CREST-positive kinetochores. These findings confirm the clastogenic effect of busulphan and reveal a considerable capability of this agent to induce aneuploidy. These results are examined taking into account the high incidence of secondary neoplasias induced by chemotherapy with alkylating agents utilized against primary neoplasias.

Chromosomal characteristics of chronic and blastic phase of chronic myeloid leukemia. A study of 100 patients in India

We report the cytogenetic findings of 100 patients with chronic myeloid leukemia (CML) [72 patients in chronic phase (CP) and 28 patients in blastic phase (BP)]. Of the 95 Ph + patients, six had Ph variant translocations involving chromosomes 1, 6, 7, 10, and 12. The percentage frequency of patients with chromosomal changes other than Ph was 7.3%. The additional aberrations (e.g., + Ph, + 8, i(17q), and + 19 were observed in 66.6% of BP patients. Of these anomalies, the frequency of + Ph and + 19 was higher in our patients than the incidence reported in literature. The association of + Ph and + 19 in patients with extramedullary T-cell blast crisis is an unusual finding as compared with reports in the literature and could be explained by geographic heterogeneity. The extra chromosomal abnormalities were almost absent in lymphoid blast crisis patients with blast phenotype of common acute lymphoblastic leukemia (ALL) type. Discrepancies were noted in different tissues (bone marrow and lymph node) in patients with extramedullary blast crisis of both myeloid and lymphoid type. These findings indicate the cytogenetic correlation with clinical and morphological picture, which consequently implicates the diagnostic and prognostic significance of chromosomal aspects.

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

Among 77 unselected patients with chronic myelogenous leukaemia (CML), 70 had Philadelphia chromosome (Ph1) in blood cells. Extra chromosomal abnormalities were noted in 4%, 55% and 78% of Ph1-positive patients in chronic phase, accelerated phase and acute blast crisis, respectively. Rearrangement of the bcr was detected in 46 of 47 Ph1-positive patients studied and also in three of five Ph1-negative ones. The locations of the breakpoints were mapped to one of four zones of the bcr in 45 patients. The median duration from diagnosis of CML to onset of acute blast crisis was not significantly different between the two groups of patients with breakpoints in the 5' portion (34 months), and in the 3' portion (39 months) of the bcr. In addition, the locations of the breakpoints within the bcr did not change as the disease progressed in the six patients who had DNA analysed both in the chronic phase and subsequently in transformation. In one of them, an additional aberrant band which was not present in the beginning of the acute phase was detected in blood cells taken 2 months later. It is suggested from the studies that transformation of CML may not be related to alterations within the bcr.

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.

Translocation 3;21 in Philadelphia chromosome positive chronic myeloid leukemia at diagnosis

We describe a further case of Philadelphia chromosome-positive chronic myeloid leukemia with a t(3;21)(q26.2;q22) present in the chronic phase. Blastic transformation occurred 8 months after presentation. The presence of the t(3;21) may indicate a poor prognosis.

Chromosomal characteristics of Ph-positive chronic myelogenous leukemia in transformation. A study of 23 Chinese patients in Taiwan

Cytogenetic study was performed in the past 3 years on 23 Chinese patients with Philadelphia chromosome (Ph) positive chronic myelogenous leukemia (CML) in transformation; seven were in accelerated phase and 16 in acute blast crisis. Chromosomal abnormalities in addition to Ph were found in three (43%) of the patients at accelerated phase and 14 (88%) of the patients at blast crisis. The common nonrandom chromosomal aberrations were double Ph, trisomy 8, trisomy 19, and trisomy 21, which occurred in 47%, 41%, 35%, and 29%, respectively, of the total patients with extra chromosomal abnormalities. Isochromosome for the long arm of chromosome 17 was found in only one patient. In patients with blast crisis, the type of blast cell was characterized through morphologic, cytochemical, and immunocytochemical studies. Eleven cases were classified as myeloid and five as lymphoid transformation. Trisomy 8, 19, and 21 were detected only in patients with myeloid blast crisis. This study also revealed a high incidence of trisomy 21 and a low incidence of i(17q) in Chinese patients with transformation of CML.

Possible cytogenetic distinction between lymphoid and myeloid blast crisis in chronic granulocytic leukemia

This study consists of 25 patients with chronic granulocytic leukemia in blast crisis (BC) or with acute leukemia who had a Ph1 chromosome and one or more other chromosome abnormalities and who were investigated by cytochemistry and immunocytochemistry techniques to determine whether the predominant blasts were myeloid or lymphoid. The disorder was myeloid in 15 patients, lymphoid in 8, and mixed in 2. Among the 15 patients with myeloid disorders, 13 (86.6%) had an additional Ph1 chromosome, i(17q), +8, +19, or some combination of these abnormalities. None of the eight patients with a lymphoid disorder had +8, +19, or i(17q), but one had an additional Ph1 chromosome. Among the eight patients with lymphoid disorders, two had structural abnormalities of chromosome 7 and two were monosomy 7. None of the patients with myeloid disease had a structurally abnormal chromosome 7, but one was monosomy 7. Our findings suggest that the number of chromosomes in an abnormal clone may be unreliable for distinguishing between lymphoid and myeloid BC. Most patients with myeloid disease had only abnormal metaphases, whereas many patients with lymphoid disorders had both normal and abnormal metaphases. This finding may partially explain why many patients with lymphoid BC respond better to treatment than do those with myeloid BC.

Translocation (3;21) in Philadelphia chromosome-positive chronic myelogenous leukemia prior to the onset of blast crisis

Two female patients in the chronic phase of CML were found to have, in addition to t(9;22), a new karyotypic abnormality--t(3;21)(q26;q22)--present in bone marrow cells. At diagnosis, this abnormality was observed in a small number of marrow cells in both patients, and as the disease progressed in patient 1, the percentage of cells showing t(3;21) was increased, reaching 100% as the transformation to blast crisis occurred. These observations suggest that t(3;21) may represent a new and rare nonrandom rearrangement which may be identified prior to the onset of blast crisis.

Origin of near-haploidy in malignant hematopoietic cells

Hyperdiploidy is common in neoplastic diseases but severe hypodiploidy or near-haploidy is extremely rare. Acute lymphocytic leukemia (ALL) and blast phase of chronic myelocytic leukemia (BC/CML) are the two most common leukemias where metaphases with as low as 23 chromosomes have been reported. Recent studies have indicated that during the course of malignant development, cells undergo numerous changes, however, it is still not known whether malignant transformation proceeds or results from the near-haploid state. Retrospectively, we have examined 100 metaphases with chromosome counts of 23 to 35 in patients with CML who have not yet progressed to the blastic phase, to see whether such metaphases share any common characteristics with published cases. The unusual behavior of chromosomes 8, 17 and the presence of Ph-chromosomes in 85% of the cells are highly unique features in our study. These observations are compatible with those found in BC/CML patients reported earlier. Therefore, it is hypothesized that selective chromosome loss is a gradual phenomenon and one of these near-haploid clones may replace a diploid clone as the dominant component of the population during blast transformation. Several hypotheses are proposed as to the origin of such clones in malignant hematopoietic stem cells.

Ring chromosomes in chronic myelogenous leukemia: an ominous finding

Two cases of Philadelphia chromosome positive chronic myelogenous leukemia (CML) demonstrated ring chromosomes. The appearance of the ring coincided with evolution from the stable to the aggressive phase. A literature search yielded six other cases of ring chromosomes in CML; all were in or were entering the aggressive phase of the disease. Thus, as is the case with acute nonlymphocytic leukemia, in CML the finding of an acquired ring chromosome is associated with a poor prognosis.

Sequential karyotype study on Ph-positive chronic myelocytic leukemia. Significance of additional chromosomal abnormalities during disease evolution

Twenty-eight patients with Ph-positive chronic myelocytic leukemia (CML), who all died of the disease, had cytogenetic studies throughout the progression of the disease: at diagnosis, during chronic phase (CP), accelerated phase (AP), and blastic transformation (BT). The aim of this sequential study was to appreciate the frequency and the significance of additional chromosomal abnormalities (ACA) during CML evolution, especially in the CP. In our series ACA were rare (five of 28 patients) and simple (four of five) in CP. They were much more frequent and complex in AP (11 of 16) and in BT (22 of 24) with complex abnormalities (13 of 24). In CP, ACA predictive value for metamorphosis was poor: only three of 13 patients had ACA within 1 year before BT, and only two of 11 within 1 year before AP. ACA were mainly observed during the last period before BT: ten of 17 patients studied within 6 months prior BT had ACA, but by then two of three were in AP. ACA, especially when complex, appear to be a hallmark of CML metamorphosis.

Oncogene activation by chromosomal rearrangement in chronic myelocytic leukemia

A considerable number of human tumors, especially leukemias and lymphomas is associated with a consistent specific chromosome translocation. At a number of the breakpoint regions of these specific aberrations are c-oncogenes (c-onc) located. The structure and/or expression of some of these c-onc is altered as a result of the specific translocation. In the CML-specific (9;22) translocation the transposition of the c-abl oncogene to the chromosome 22 bcr sequences results in the production of a chimeric bcr/c-abl fusion protein. This result strongly suggests that tumor-specific chromosomal aberrations can lead to the activation of cellular oncogenes.

The karyotype of blastic crisis

The nonrandomness of chromosome clonal evolution in blastic crisis of chronic myeloid leukemia is well established, with three major changes [+8, +Ph, i(17q)] occurring alone or in combination in over 70% of the patients. The chromosome changes observed in different tissues may reveal the origin of the abnormal clones, as well as provide evidence for distinct or common evolution by different cell populations. The significance of the chromosome abnormalities and their relationship to blastic conversion are discussed. In general, chromosome evolution may be considered a rather reliable predictive or diagnostic parameter of blastic crisis but both the nature and the subsequent behavior of abnormal clones appear to be of critical value. As to the clinical/chromosome correlations, a few major points have emerged: the i(17q) aberration is mostly associated with signs of myeloid differentiation of blasts and a marked basophilia; it is mainly observed in the late stage of the disease, but overall median survival of patients with this marker is usually long; more atypical or complex changes usually are associated with a worse prognosis; patients with only a Ph in their blasts may have a longer survival, at least in some cytologic subgroups; and d) the loss of the Y chromosome seems to protect the cell against further clonal evolution. Finally, the relevance of the chromosome changes in the multistage process of blastic conversion is discussed, and the breakpoints of secondary changes recorded so far are reviewed and examined. It appears that certain chromosome regions are more often affected; these might contain genes of critical importance for the final malignant progression. Molecular biology may provide insight, in the future, on the nature and expression of involved genes.

Karyotype evolution in CML: high frequency of translocations other than the Ph

The karyotypes of 33 Philadelphia-positive chronic myelogenous leukemia patients during the blastic phase are reported. Only three patients (9%) had a Philadelphia clone without further chromosomal aberrations, whereas, all the others had karyotype evolution. Aside from some nonrandom abnormalities (+8, i(17q), +Ph, +19) we found a higher frequency of clones with random structural rearrangements (13 cases, 39.4%) than previously reported. From a clinical point of view, however, the additional chromosomal (structural) abnormalities do not significantly influence the patients' survival.

Isochromosome 17q in a case of myelofibrosis with myeloid metaplasia terminating in blastic transformation

A case of myelofibrosis with myeloid metaplasia in a 61-year-old female patient is reported. Cytogenetic studies were performed using short-term culture without phytohemagglutinin. A chromosomal aberration of an isochromosome 17q, [i(17q)], was revealed in 88% of the metaphases of peripheral blood cells in the blastic phase. However, all metaphases of bone marrow cells in the chronic phase showed a normal karyotype. Furthermore, i(17q) was also observed in 10% of the metaphases of spleen cells examined 8 months before blastic transformation. In this case, therefore, the cells with i(17q) were associated with an abnormal clone of blastic transformation, with the abnormal clone originating in the spleen with myeloid metaplasia.

Multiple recurrent genomic defects in follicular lymphoma. A possible model for cancer

Several steps in the clinical evolution of human neoplasia are associated with a variety of recurrent chromosomal defects that could prove essential to the understanding of cancer. We found 15 types of nonrandom chromosomal abnormalities in a study of 71 patients with follicular lymphoma; 10 of the types appeared to influence the histopathological findings, clinical course, or response to treatment. A translocation, t(14;18), observed in 85 percent of all patients appeared to be the main determinant of a follicular pattern. Ten patients with a t(14;18) as a single defect had the histologic features of follicular small cleaved-cell lymphoma. Most did not require treatment for one to four years, because their tumors had an initial indolent course. In contrast, patients with follicular small cleaved-cell lymphoma with t(14;18) and deletion 13q32 acquired the hematologic features of leukemia and had an acceleration of the disease. A deletion 6q together with a complete or partial trisomy 7 or trisomy 12 (or both) was associated with the clinically more aggressive follicular mixed small- and large-cell or large-cell histologic type, which often evolves from follicular small-cell lymphoma. A complete or partial trisomy 3, 18, or 21 correlated almost exclusively with follicular large-cell lymphoma. In all follicular stages, a trisomy 2 or duplication 2p often accompanied an accelerated clinical course and a poor response to treatment. This study suggests that several discrete genomic defects may govern the evolution of a patient's malignant disease.