Cytogenetic response to autografting in chronic myelogenous leukemia correlates with the amount of BCR-ABL positive cells in the graft

Molecular genetic analysis of haematological malignancies: I. Acute leukaemias and myeloproliferative disorders

Molecular genetic techniques are now routinely applied to haematological malignancies within a clinical laboratory setting. The detection of genetic rearrangements not only assists with diagnosis and treatment decisions, but also adds important prognostic information. In addition, genetic rearrangements associated with leukaemia can be used as molecular markers allowing the detection of low levels of residual disease. This review will concentrate on the application of molecular genetic techniques to the acute leukaemias and myeloprolferative disorders.

Specific killing of Ph+ chronic myeloid leukemia cells by a lentiviral vector-delivered anti-bcr/abl small hairpin RNA

Chronic myeloid leukemia (CML) is characterized by a reciprocal chromosomal translocation between chromosomes 9 and 22 t(9;22)(q34;q11) that causes fusion of the bcr and abl genes. Transcription and splicing of the fusion gene generate two major splice variants of the bcr/abl transcript that encode an oncoprotein with tyrosine kinase activity. We have taken advantage of lentiviral vectormediated delivery of anti-bcr/abl short hairpin RNAs (shRNA) to downregulate the bcr/abl transcript in Philadelphia chromosome-positive (Ph+) K562 leukemia cells. This downregulation caused complete inhibition of proliferation of these cells and was accompanied by >90% inhibition of the bcr/abl transcript and p210 protein. These results demonstrate the feasibility of using a lentiviral vector to stably transduce therapeutic shRNAs into leukemia cells for the potential ex vivo purging of Ph+ cells in an autologous hematopoietic cell transplant setting. Furthermore, the robust expression of the shRNAs from our lentiviral vector suggests that this system could be generally useful for the expression of other shRNAs.

Chronic myelogenous leukemia: elements of conventional chemotherapy and an overview of autografting in the treatment of the chronic phase

Chronic myelogenous leukemia (CML) consists of a clonal malignancy that arises from a pluripotent hematopoietic stem call. In most cases, neoplastic cells are characterized by the formation of a shortened chromosome 22 called the Philadelphia chromosome. It results from a reciprocal translocation between long arms of chromosomes 9 and 22. A rearranged gene (bcr-abl) is the consequence of this translocation, and it may be considered as the first step toward leukemic transformation. Conventional chemotherapy of CML in the chronic phase is unable to suppress the Ph+ leukemic clone. The treatment with the IFNalpha may induce an overall cytogenetic response rate of 40-50% of patients. Autografting for patients with CML in chronic phase may induce a 53% overall cytogenetic response rate with a duration of disease-free time and survival from the autograft ranging, respectively, from 4 to 24 mo and from 8 to 40 mo.

Enrichment of normal progenitors in counter-flow centrifugal elutriation (CCE) fractions of fresh chronic myeloid leukemia leukapheresis products

OBJECTIVES

The aim of this study was to assess the suitability of a technique based on counter-flow centrifugal elutriation (CCE), which should allow one to enrich chronic myeloid leukemia (CML) patients' unstimulated native leukapheresis product (nLP) in CD34+ HLADR- cells and BCR-ABL negative cells.

METHODS

Six newly diagnosed CML patients were subjected to leukapheresis, and the products were subfractionated with the use of CCE. nLP and all fractions were studied for the presence of CD34+ cells and a proportion of BCR-ABL fluorescence in situ hybridization (FISH)+ cells.

RESULTS

CCE fractions with a high flow rate contained the highest proportion of CD34+ cells [mean (SEM) 6.89% (3.88)]. However, CD34+ cells present in low-rate CCE fractions showed a higher proportion of HLADR-[49.6% (13.5 in 70 mL min-1) and 21.5% (11.6 in 110 mL min-1)] than those in 170 mL min-1[3.2% (2.5)] and "rotor off" [3.4% (1.9)]. This was associated with lower proportions of BCR-ABL FISH+[8.1% (4.8) and 1.9 (1.7)] and smaller BCR-ABL to ABL transcript ratios [0.58 (17) and 0.26 (0.08) in 70 and 110 mL min-1] fractions as compared to 140 and 170 mL min-1 fractions [21.6% (5.2) and 31.6% (15.3) for BCR-ABL FISH+ cells and 0.75 (0.16) and 0.90 (0.24) for BCR-ABL/ABL]. Fractions with the lowest proportions of BCR-ABL-positive cells and the lowest BCR-ABL/ABL transcript ratios (110 mL min-1) contained from 1.3 x 106 to 82.7 x 106 (median: 3.97 x 106) CD34+ cells.

CONCLUSIONS

In the present study we have shown that CCE may be used effectively to obtain nLP fractions enriched in normal hematopoietic progenitors.

Minimal residual disease in chronic myeloid leukaemia patients

In many ways, chronic myeloid leukaemia (CML) serves as a paradigm for the utility of molecular methods in the diagnosis of malignancy or for monitoring the response of the patient to therapy. The Philadelphia (Ph) translocation provides an elegant example of how cytogenetic findings provided the starting point for understanding the genetic mechanisms involved in leukaemogenesis. The degree of reduction in tumour load after therapy is an important prognostic factor for CML patients. Several approaches have been introduced that can specifically detect the Ph translocation or its products; these approaches include fluorescent in situ hybridization, Southern blotting, western blotting and reverse transcriptase polymerase chain reaction (RT-PCR). Because non-quantitative RT-PCR analysis after therapy gives only limited information, quantitative or semiquantitative RT-PCR assays have been developed that enable the kinetics of residual BCR-ABL transcripts to be monitored over time in patients after allogeneic stem cell transplantation, interferon-alpha, or STI571 therapy.