The clinical application of molecular techniques in Philadelphia-positive leukaemia

Value of fluorescence in situ hybridization for detecting the bcr/abl gene fusion in interphase cells of routine bone marrow specimens

Fluorescence in situ hybridization (FISH) is a new technique that allows demonstrating of the bcr/abl gene fusion in bone marrow cells of patients with Philadelphia translocation (Ph)-positive chronic myeloid leukemia (CML). In this study, bone marrow samples of 150 patients were investigated routinely by interphase FISH, cytogenetics, and bone marrow histopathology. In 20 patients with reactive hyperplasia of the granulopoiesis and normal karyotypes, FISH revealed nonspecific bcr/abl fusion signals at a mean frequency of 2.7% of the cells examined. The cutoff level for specific fusion signals was set at three times the standard deviation (9.0%). None of the 29 cytogenetically Ph-negative patients with myeloproliferative disease other than CML had fusion signals exceeding 9%. The mean frequency of specific fusion signals in nontreated patients with CML (n = 59) was 92.7%, and 49.3% in patients with CML who received therapy (n = 42). For diagnosing Ph-positive CML, interphase FISH has been faster, more reliable, and more sensitive than cytogenetics, which was successful in 54 of 59 patients investigated at first diagnosis but only in 27 of 42 patients receiving therapy, and it failed to detect Ph-positive cells in three patients with CML. However, small percentages of less than 9.0% of cells with bcr/abl fusion signals were below the threshold of interphase FISH, thereby limiting its use for detecting minimal residual disease.

Myelodysplasia and the leukemias

The armistice after World War II marked the beginning of an era that was to last to the end of the present century. It was an era in which many changes in medicine and nursing combined to alter the entire philosophy of managing malignant disease. More specifically, the fluid-phase tumors, which comprise myelodysplasia and the leukemias, were singled out for special attention. First there was the ease with which blood and bone marrow could be sampled, making serial investigations simple and practical. Second, cytotoxic drugs became available ranging from nitrogen mustard through cytosine arabinoside, the anthracycline antibiotics, and the epi-podophyllotoxins. Although cytomorphology of the hematopoietic tissue had been exquisitely defined with the use of Romanowsky stains coupled with electron microscopy, the diagnosis of leukemia was, before 1945, a death sentence for want of effective therapy. This changed dramatically with the introduction of the folate antagonists, and progress was unremitting as the range of new products expanded. Suddenly responses could be obtained with single agents, and fairly rapidly combinations were developed for cumulative antitumor effect. Many agents had undesirable toxicity among different organs. Although slightly different for myeloblastic or lymphoblastic variants, this approach produced apparent disease eradication. The concept of complete remission, both clinical and hematologic, was born. Some of our early enthusiasm has had to be tempered with the somber appreciation that not all patients can improve and many others experience relapses. Where then do we stand? Leukemic cells themselves seldom kill. It is the relentless and uncontrolled expansion of a neoplastic clone that leads to bone marrow failure, albeit at different rates in the various subtypes. In the acute forms, the common presentation remains symptomatic anemia, neutropenic sepsis, and thrombocytopenic bleeding. Differentiation from marrow aplasia may not be possible at first on clinical grounds, although bone tenderness, gingival hypertrophy, and skin infiltration are among the general useful differential signs. Findings in the circulation and the marrow are of cardinal importance in diagnosis; they provide the basis for classification. Improved accuracy has followed the introduction of cytochemical stains, and a widening range of monoclonal antibodies, and greater recourse to karyotyping, have enhanced diagnostic acumen. Treatment decisions rest on many variables or prognostic factors that include age, performance status, comorbidity, and disease category, with an ever increasing regard for the part played by cellular and molecular genetics. Despite skillful utilization of this wealth of information for optimal management, outcome often leaves much to be desired. Myelodysplasia encompasses a number of different syndromes in which the refractory anemias are indolent, whereas those with excess blasts progress toward overt leukemia. Considerable judgment is necessary in selecting patients for whom supportive therapy alone is appropriate and recognizing others, up to one third of patients for whom use growth factors that include erythropoietin, granulocyte or granulocyte monocyte-colony stimulating factors, and thrombopoietin can be justified. The often unfavorable result has been a stimulus to current investigations that examine the value of intensive chemotherapy or the more innovative bone marrow transplantation and its peripheral blood equivalent. Autografting is a newer alternative that does not have proved potential. Acute leukemia, whether myeloblastic or lymphoblastic, has been managed with mixed success. Remission rates have steadily increased and, notably among children, moved toward 100% in certain groupings. The downside of nonspecific drug regimens is that some patients simply may not respond, whereas others experience remissions and then relapses. (ABSTRACT TRUNCATED)

Southern technique and cytogenetics are complementary and must be used together in the evaluation of Ph1, M-BCR positive chronic myeloid leukemia (CML) patients treated with alpha interferon (IFN-alpha)

Cytogenetic analysis is the gold standard for the follow-up of CML patients. The sensitivity of cytogenetics is fairly similar to that of Southern detection of M-BCR rearrangement (5%); this last technique has the potential advantage of being independent of cell division and yield of metaphases. IFN alpha treatment can induce lack of growth of hemopoietic precursors and poor yield of metaphases has been observed. For this reason we decided to study the grade of concordance and complementarity between analysis of karyotype and detection of M-BCR rearrangement of Southern blot. We studied 43 Ph1 positive, M-BCR positive pre-BMT CML patients (48 samples) treated with IFN alpha 2a. Karyotype was done on bone marrow cells by direct method, culture, and banding. Southern technique was performed onto DNA from peripheral blood leukocytes treated with BgIII (and Xbal if necessary) and hybridized with the universal probe (Ph1/bcr-3, Transprobe 1) labelled with dCTP32. A highly significant association between both tests was obtained. Of 48 samples analyzed, 34 were evaluable by both methods and 28 gave the same result for both tests. The concordance between the tests was good (kappa index: 0.63). Of total samples 27.1% was not evaluable by cytogenetics; this figure was 31.2% in samples from patients who were previously in complete cytogenetic response. All of the specimens not evaluable by karyotyping were evaluable by Southern. One sample was not analyzable by Southern but it was evaluable by cytogenetic analysis. The information obtained by Southern technique was clinically relevant, and decisions were made according to its results. We conclude that both tests show a significant association and a good concordance, although they are not interchangeable. Cytogenetic and molecular studies are complementary and must be employed together in CML patients treated with alpha-interferon.

The role of natural killer cells in the treatment of chronic myeloid leukemia

The success of chemotherapy in patients with leukemia whose marrow appears to be replaced by leukemia cells must be due to the persistence of normal stem cells. In this normal population are the progenitors of the cells of the immune system. Natural killer (NK) cells originate in the bone marrow. On maturation and activation with interleukin 2 (IL-2) or other cytokines, NK cells develop cytotoxic activity against a variety of leukemic blasts, including those from patients with chronic myeloid leukemia (CML). In the past few years, bone marrow transplantation (BMT) and alpha-interferon (IFN-alpha) have proved to be the most promising therapies for the treatment of CML. In both these therapies, NK cells may play a prominent role. In this article, we discuss the antitumor/antileukemia activity of human NK cells, the presence of benign NK cell precursors in the different stages of CML, the role of NK cells in BMT and IFN-alpha treatment, and the potential therapeutic applications of NK cells in patients with hematologic malignancies.

Studies on hemopoietic chimerism following allogeneic bone marrow transplantation in the molecular biology era

Donor hematopoiesis or donor chimerism in the host following allogeneic bone marrow transplantation (BMT) has appeared crucial to the engraftment process. However, as molecular techniques exploiting neutral variation in human genetic material have been used in the study of chimerism, the detection of residual host cells or mixed hemopoietic chimerism has indicated that donor chimerism is not obligatory following BMT. This review focuses on the detection and significance of mixed chimerism (MC) in patients transplanted for both malignant and non-malignant hemopoietic disease and attempts to tease out the contribution of MC to engraftment, leukemia relapse, graft rejection and long-term disease-free survival.

Spontaneous loss of Ph chromosome with maintenance of clonal hemopoiesis in an untreated patient with myeloproliferative disease and a long survival

The unusual case of myeloproliferative disease described here is characterized by the following features: (1) a clinically completely silent course for 11 years without splenomegaly, marrow fibrosis, or cellular morphologic alterations; (2) the presence, at the onset, of a Philadelphia (Ph) chromosome without DNA breakpoints in the M-bcr region; (3) the spontaneous loss of detectable Ph-positive cells, 5 years after the first finding of leukocytosis, in the absence of any therapy; (4) the maintenance of the clonal nature of hematopoiesis, as revealed by the PGK X-linked inactivation pattern, in the absence of the Ph chromosome; and (5) a biphasic trend in the levels of leukocytes, red cells, and platelets during the years of observation.

Detection of minimal residual disease after sex-mismatch bone marrow transplantation in chronic myelogenous leukemia by fluorescence in situ hybridization

Detection of minimal residual disease is one of the major goals in bone marrow transplantation. We used a fluorescence in-situ hybridization technique to detect residual Philadelphia-chromosome positive cells in chronic myelogenous leukemia (CML) patients after sex-mismatch BMT. We analyzed the level of detection using probes for the BCR/ABL fusion product by comparison with results obtained with probes for the Y and X sex chromosomes. Detection of sex-mismatch chromosomes was significantly higher than that of the BCR/ABL translocation. In contrast, a higher specificity of residual tumor cell detection by the BCR/ABL probe was demonstrated because most of the sex-mismatch cells detected by FISH had a normal karyotype. Tumor-specific markers probes are thus superior and more accurate than sex-mismatch probes for detection of MRD in CML patients after BMT.

Clinical detection of BCR-abl fusion by in situ hybridization in chronic myelogenous leukemia

We describe the use of the fluorescence in situ hybridization (FISH) technique to detect residual Philadelphia chromosome-positive (Ph+) cells in a patient with blastic phase chronic myelogenous leukemia (CML) after aggressive cytoreductive treatment. The analysis was made in interphase nuclei because of the very small number of recognizable metaphases in leukemic patients. FISH was a reliable tool for the detection of chromosome translocations in interphase nuclei as compared with conventional cytogenetic and polymerase chain reaction (PCR) techniques.

Philadelphia chromosome-positive leukaemia: the translocated genes and their gene products

Overwhelming evidence indicates a role for the deregulated ABL protein tyrosine kinase in the aetiology of CML and Ph-positive acute leukaemia. These disorders are characterized by the generation of BCR/ABL fusion proteins with elevated tyrosine kinase activity. Although much is known concerning the transforming potential of ABL proteins in various systems, very little is understood of the normal function and mode of regulation of ABL activity. The mechanism of oncogenic activation is therefore also obscure. In spite of this, our understanding of the molecular details of these chromosomal translocations allows the design of therapies directed against their unique, leukaemia-specific proteins and RNA products.