Acute myeloblastic leukaemia without Philadelphia chromosome developing after interferon therapy for chronic myelocytic leukaemia with Philadelphia chromosome

Evolution of T-cell clonality in a patient with Ph-negative acute lymphocytic leukemia occurring after interferon and imatinib therapy for Ph-positive chronic myeloid leukemia

Introduction

The development of Philadelphia chromosome (Ph) negative acute leukemia/myelodysplastic syndrome (MDS) in patients with Ph-positive chronic myeloid leukemia (CML) is very rare. The features of restrictive usage and absence of partial T cell clones have been found in patients with CML. However, the T-cell clonal evolution of Ph-negative malignancies during treatment for CML is still unknown.

Objective

To investigate the dynamic change of clonal proliferation of T cell receptor (TCR) Vα and Vβ subfamilies in one CML patient who developed Ph-negative acute lymphoblastic leukemia (ALL) after interferon and imatinib therapy.

Methods

The peripheral blood mononuclear cells (PBMC) samples were collected at the 3 time points (diagnosis of Ph-positive chronic phase (CP) CML, developing Ph-negative ALL and post inductive chemotherapy (CT) for Ph-negative ALL, respectively). The CDR3 size of TCR Vα and Vβ repertoire were detected by RT-PCR. The PCR products were further analyzed by genescan to identify T cell clonality.

Results

The CML patient who achieved complete cytogenetic remission (CCR) after 5 years of IFN-α therapy suddenly developed Ph-negative ALL 6 months following switch to imatinib therapy. The expression pattern and clonality of TCR Vα/Vβ T cells changed in different disease stages. The restrictive expression of Vα/Vβ subfamilies could be found in all three stages, and partial subfamily of T cells showed clonal proliferation. Additionally, there have been obvious differences in Vα/Vβ subfamily of T cells between the stages of Ph-positive CML-CP and Ph-negative ALL. The Vα10 and Vβ3 T cells evolved from oligoclonality to polyclonality, the Vβ13 T cells changed from bioclonality to polyclonality, when Ph-negative ALL developed.

Conclusions

Restrictive usage and clonal proliferation of different Vα/Vβ subfamily T cells between the stages of Ph-positive CP and Ph-negative ALL were detected in one patient. These changes may play a role in Ph- negative leukemogenesis.

Philadelphia-negative clonal hematopoiesis following imatinib therapy in patients with chronic myeloid leukemia: a report of nine cases and analysis of predictive factors

There are increasing reports of Philadelphia-negative (Ph-negative) clonal hematopoiesis developing among patients with chronic myeloid leukemia (CML) treated with imatinib mesylate (IM). To establish the incidence and significance of these chromosomal abnormalities, we analyzed data on 141 consecutive patients with CML treated with IM at the British Columbia Cancer Agency and Vancouver General Hospital from 1999 to 2004. The cumulative incidence of developing a Ph-negative clone three years from the start of IM was 8.7% at a median of 13.3 months. The Ph-negative clonal abnormalities included monosomy 7 and/or trisomy 8 (seven patients), monosomy for chromosomes X and 22 (one patient), and a (12;16) translocation (one patient). Two of the patients presented with the same chromosomal abnormality in both Ph-negative and Ph-positive cells. None of the Ph-negative clonal abnormalities was associated with myelodysplasia. In a multivariate analysis, an interval from diagnosis to initiation of IM of 1 year or less was associated with an increased risk of developing a Ph-negative clone (relative risk = 20.2; P = 0.025). There was no difference, however, in event-free survival between patients who did and did not develop Ph-negative clones. Therefore, while the development of Ph-negative clonal hematopoiesis in patients with CML treated with IM is uncommon, it appears to be more frequent than that previously seen with IFN, but it does not seem to confer a worse prognosis.

Random aneuploidy in CML patients at diagnosis and under imatinib treatment

Chronic myeloid leukemia (CML) is characterized by the presence of a BCR-ABL fusion gene, which is the result of a reciprocal translocation between chromosomes 9 and 22, and is cytogenetically visible as a shortened chromosome 22 (Philadelphia). Research during the past two decades has established that BCR-ABL is probably the pathogenetic pathway leading to CML, and that constitutive tyrosine kinase activity is central to BCR-ABL capacity to transform hematopoietic cells in vitro and in vivo. The tyrosine kinase inhibitor imatinib mesylate was introduced into the treatment regimen for CML in 1998. During the last few years, reports on chromosomal changes during imatinib treatment have been described. In this study, we evaluated the random aneuploidy rate with chromosomes 9 and 18 in bone marrow from treated and untreated patients. We found higher aneuploidy rates in both treated and untreated patients compared to the control group. In three patients who were treated with imatinib mesylate for more than 1.5 years, triploidy also appeared in some nuclei. To our knowledge, this is the first report on new chromosomal changes such as random aneuploidy and triploidy under imatinib treatment, but more studies are needed to investigate the long-term effect of the imatinib treatment on genetic instability.

Myelodysplastic syndromes and acute leukemia developing after imatinib mesylate therapy for chronic myeloid leukemia

During therapy with imatinib, some patients with chronic myeloid leukemia (CML) develop chromosomal abnormalities in Philadelphia chromosome (Ph)-negative cells. These abnormalities are frequently transient and their clinical consequence is unclear. Although some reports have suggested that the abnormalities might be associated with secondary myelodysplastic syndrome (MDS), the diagnosis has not always been established using standard criteria. We report 3 cases of patients treated with imatinib for CML who were subsequently found to have chromosomal abnormalities in Ph-negative cells. One of them developed acute myelogenous leukemia (AML) and the other 2 developed high-risk MDS that rapidly transformed to AML. These cases were identified in a total study group of 1701 patients. Although these occurrences are rare, the findings highlight the need for close monitoring of patients with CML treated with imatinib.

Induction of centrosome and chromosome aberrations by imatinib in vitro

Imatinib (STI571, Gleevec/Glivec) is a potent selective tyrosine kinase inhibitor and is used successfully in the treatment of chronic myeloid leukemia (CML). While karyotype alterations, in addition to the Philadelphia chromosome, are a common phenomenon of progressing CML, the observation of BCR-ABL-negative leukemic clones with distinct aberrant karyotypes under an imatinib regimen is not yet understood. Here we test the hypothesis that such tumor clones may be induced de novo from normal cells by imatinib. In vitro experiments with varying drug concentrations (5-20 microM) were performed on normal human dermal fibroblasts (NHDF), Chinese hamster embryonal and Indian muntjak fibroblasts. After 3 weeks of treatment, analysis of cell cultures by centrosome immunostaining and conventional cytogenetics revealed that imatinib induced centrosome and chromosome aberrations in all cultures in a significant dose-dependent and species-independent manner. Moreover, the results of NHDF long-term culture experiments demonstrated that aberrant phenotypes, emerging under imatinib treatment for 12 weeks, were not reversible after prolonged propagation omitting the drug. These observations suggest a causative role of imatinib in the origin of centrosome and karyotype aberrations (genetic instability) and thus may explain the emergence of clonal chromosomal abnormalities in BCR-ABL-negative progenitor cells under imatinib therapy.

Clonal evolution in chronic myelogenous leukemia

Clonal evolution (CE) may be a marker of disease progression in chronic myelogenous leukemia (CML) and is thought to reflect the genetic instability of the highly proliferative CML progenitors. The frequency of CE increases with advancing stage, rising from 30%in accelerated phase and up to 80% in blast crisis. Given its association with disease progression, CE is considered a feature that defines accelerated-phase CML; however, not all studies have demonstrated a uniformly poor outcome for patients with CE. Chromosomal abnormalities in Ph chromosome negative metaphases increasingly have been recognized in patients treated with imatinib. The true incidence of this phenomenon is not clear but appears to occur in 2% to 17% of imatinib-treated patients. Regardless of the precise mechanism and the long-term clinical implications, the findings described in this article underscore the importance of routine cytogenetic analysis for patients treated with imatinib. The continued study of these phenomena will help us to understand better the pathogenesis of CML and improve the long-term treatment of patients with CML.

Report of 34 patients with clonal chromosomal abnormalities in Philadelphia-negative cells during imatinib treatment of Philadelphia-positive chronic myeloid leukemia

Imatinib mesylate (Gleevec), an inhibitor of the BCR-ABL tyrosine kinase, was introduced recently into the therapy of chronic myeloid leukemia (CML). Several cases of emergence of clonal chromosomal abnormalities after therapy with imatinib have been reported, but their incidence, etiology and prognosis remain to be clarified. We report here a large series of 34 CML patients treated with imatinib who developed Philadelphia (Ph)-negative clones. Among 1001 patients with Ph-positive CML treated with imatinib, 34 (3.4%) developed clonal chromosomal abnormalities in Ph-negative cells. Three patients were treated with imatinib up-front. The most common cytogenetic abnormalities were trisomy 8 and monosomy 7 in twelve and seven patients, respectively. In 15 patients, fluorescent in situ hybridization with specific probes was performed in materials archived before the initiation of imatinib. The Ph-negative clone was related to previous therapy in three patients, and represented a minor pre-existing clone that expanded after the eradication of Ph-positive cells with imatinib in two others. However, in 11 patients, the new clonal chromosomal abnormalities were not detected and imatinib may have had a direct effect. No myelodysplasia was found in our cohort. With a median follow-up of 24 months, one patient showed CML acceleration and two relapsed.

Acute lymphoblastic leukemia without the Philadelphia chromosome occurring in chronic myelogenous leukemia with the Philadelphia chromosome

The blast crisis in chronic myelogenous leukemia (CML) is related to the evolution of a Philadelphia chromosome (Ph)-positive clone. Secondary chromosomal abnormalities accompanied by t(9;22) are found in 70-80% of blast crises. Here we describe a patient with Ph-positive CML, who developed Ph-negative acute lymphoblastic leukemia (ALL). A 52-year-old man was diagnosed with CML with the Ph chromosome in the chronic phase. He achieved a partial cytogenetic response after 4 months of imatinib mesylate therapy. After 8 months, common ALL occurred. At that time his karyotype was normal and the Ph chromosome was not noted.

Cytogenetic studies in patients on imatinib

With the introduction of imatinib (Gleevec) (formerly STI571) for the treatment of chronic myeloid leukemia (CML), the various diagnostic methods used to monitor patients must be re-evaluated. Conventional cytogenetics has been the established method for follow-up of patients treated with interferon-alpha (IFN-alpha), and the prognostic value of major and complete cytogenetic remission was demonstrated in a number of studies. In patients on imatinib, these endpoints will likely remain valid, although longer observation is required. Cytogenetic remission as a time-dependent variable may aid risk stratification early on. Clonal evolution, ie, the presence of cytogenetic abnormalities in addition to the Philadelphia (Ph) chromosome, may provide important prognostic information as to the likely response to imatinib in all phases of CML but must be interpreted within the context of other disease characteristics. In some patients, clonal evolution is related to imatinib resistance. Information regarding the impact of specific types of additional cytogenetic abnormalities is still limited. Surprisingly, nonrandom karyotypic abnormalities have also been noted in the Ph-negative cells of some patients in cytogenetic remission. This is a novel phenomenon whose causality and prognostic implications require thorough and systematic evaluation.

Ph-negative acute lymphocytic leukemia occurring after interferon therapy for Ph-positive chronic myelocytic leukemia

We report a unique case of chronic myelocytic leukemia (CML) with the Philadelphia (Ph) chromosome. The patient obtained cytogenetic complete remission (CR) after treatment with interferon (IFN). When he transformed to acute lymphocytic leukemia (ALL), cytogenetic analysis showed that the karyotype was normal and fluorescence in situ hybridization (FISH) indicated that blast cells were Ph-negative. Immunophenotyping showed that the cells were CD34-positive and CD38-negative. Blast cells in his final stage were BCR/ABL rearrangement negative by reverse transcription polymerase chain reaction (RT-PCR).

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.