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Copy number alterations (CNAs) at 58 different loci have been investigated in 95 bone marrow or peripheral blood samples from patients with chronic myeloid leukemia (CML) or pediatric acute lymphoblastic leukemia (pALL) using multiplex ligation-dependent probe amplification (MLPA). In all but one case, the CNA profile correctly distinguished patients with CML who were in chronic phase from those in lymphoblast crisis. Within the chronic phase group, we could not separate patients resistant to imatinib therapy from those who were good responders. In our investigation of patients with pALL, a panel of MLPA probes broader than ever before was applied. Paired diagnostic and relapse samples from patients with pALL demonstrated clonally related or independent dominant clones, suggesting the presence of a pre-leukemic cell group. Identification of the origin of cell populations dominating at relapse will have a great effect on future treatment strategies. In summary, we have demonstrated the versatility of MLPA by using this cost-effective technique for two new applications., (Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.)

The t(9;22) translocation, which results in a fusion protein with abnormal tyrosine-kinase activity, plays a central role in the pathogenesis of chronic myeloid leukemia. The selective inhibition of this chimeric protein with imatinib-mesylate is an efficient therapeutic option, haematologic and cytogenetic responses can be achieved in most of the patients. The primary goal of monitoring the disease is to assess the efficiency of the therapy, to highlight those patients, whose survival may be improved by modifying treatment. Three methods are widely used for the genetic monitoring of chronic myeloid leukemia. With karyotyping, the proliferating bone marrow cells can be evaluated. The use of fluorescent in situ hybridization makes the cytogenetic analysis of each cell within the sample possible. Real-time quantitative polymerase chain reaction is capable of quantifying residual leukemia far below the sensitivity of cytogenetics. The results of these three methods have different biological meanings, thus, for the interpretation of the results, the knowledge of the characteristics, the benefits and the draw-backs of the methods is required. The present study shows the most important characteristics of these methods based on the literature and data acquired from 1165 samples of 197 patients detected by the authors.

The interferon treatment of chronic myeloid leukaemia has been monitored by investigating the tumour burden as revealed by fluorescence in situ hybridization and the expression of BCR-ABL chimera determined by quantitative reverse transcription polymerase chain reaction. These parameters were obtained from the peripheral blood of 51 untreated and 104 follow-up patient samples. Poor correlation (r=0.31) was found between BCR-ABL expression and tumor load in all samples as well as in untreated patients, and this correlation was even less in all follow-up cases (r=0.28). Regarding chimera expression five order of magnitude difference existed in the untreated patients and this value dropped to two in those with complete cytogenetic response. Only the major and the complete cytogenetic response groups differed significantly (p<0.001) in the BCR-ABL expression from that of patients at diagnosis. Among the different cytogenetic response groups the only significant difference (p<0.01) in the BCRABL expression was obtained between the major and the minor responders. In the individual patients not only correlated changes of residual tumour mass and chimera expression, but mainly independent changes of these two parameters were observed. This indicates that the BCR-ABL expression and the tumor burden are largely independent variables.

The history of a forty year old patient is presented who was admitted with a clinical picture of chronic myeloid leukemia (CML). Laboratory findings, bone marrow morphology and molecular investigations supported this diagnosis, including b3/a2 as well as b2/a2 chimeric mRNA expression in support of a Philadelphia chromosome positive chronic myeloproliferation. In a fraction of the bone marrow content, however, an infiltrate different from that of CML could be seen. In addition, the morphology, cytochemistry, immunophenotyping and molecular analysis indicated that the coexisting neoplasia is hairy cell leukemia (HCL). Cell lineage specific interphase cytogenetic analysis proved a clonal relationship between the two neoplasias in a way that the HCL arose from one of the B-cells which, based on two cytogenetic markers, belonged to the original CML clone.

The authors have treated 38 patients with chronic phase chronic myeloid leukemia in their single center in the last five years. Conventional chemotherapy provided about 40-50% hematological response, interferon-alpha seems to be more effective, complete hematological remission occurred in 65%. Interphase cytogenetics and fluorescein in situ hybridisation technique was used to measure the cytogenetic response. They observed complete cytogenetic remission in two cases (8%), major response in 11 (39%), minor response in 4 (15%) and minimal response in 4 cases (15%). Interferon-alpha is an effective, well-tolerated medicine in the treatment of chronic myeloid leukemia.

In a prospective survey clinical haematological and molecular biological data of 31 patients with chronic myelogenous leukaemia (chronic phase, CML) observed in their haematological outpatient department were analyzed. During 1996 and 1999 a regular follow-up of the Philadelphia chromosome level in treated patients was performed with molecular biological techniques, i.e. with reverse transcription polymerase chain reaction (RT-PCR) and with fluorescence in situ hybridization (FISH) methods. During the follow-up period of 33 months from the 31 patients with CML (16 males, 15 females) 25 ones were treated with human recombinant interferon-alpha (IFN), however, six others were getting only hydroxyurea (HU). During this period in three patients allogen bone marrow transplantation was performed and seven ones expired (six out of them of blastic crisis). The quality of therapeutic response at cytogenetical level was determined by decrease of the bcr-abl level due to the treatment (non-responders, major, minor and complete cytogenetic remission groups). In nine patients (five from the IFN-group, four from the HU-group) achieved no cytogenetic therapeutic response (non-responders, 29%). However, in 13 patients a minor (bcr-abl range of 60-30%), and in nine patients a maior/complete (bcr-abl of 30-10%) cytogenetic response (42% and 29%, respectively) were detected. Moreover, the quality of cytogenetic response correlated with the haematological remission. The maior/complete cytogenetic response was durable in eigth patients. The improvement of the overall survival of patients with CML, the postpone of the fatal accelerated-blastic phase could be expected only from the early introduced, in individually adjusted and given in maximally tolerated dosage of interferon (3-5 million UI/m2/day). The qualitative (RT-PCR) and quantitative (FISH) detections of the Philadelphia chromosome are reliably reproducible up-to-date molecular biological methods getting relevant results, which could be very helpful in the planning, monitoring, in setting of optimal dosage of the interferon therapy of patients with CML, in addition in the judgement of the effectiveness of the therapy, in the reduction of adverse effects, as well as in forecasting of the cytogenetic progression.

The authors have monitored the treatment of chronic myeloid leukaemia by simultaneous investigation of the residual tumour mass as well as the expression of the bcr-abl chimera. The first parameter was obtained by calculating the bcr-abl rearrangement positive cells as determined by fluorescent in situ hybridisation (FISH). The other value was determined by a quantitative (competitive) reverse transcription polymerase chain reaction (Q-RT-PCR). To avoid any inaccuracy associated with the variable yield of RNA isolation and reverse transcription, respectively, the amount of chimera mRNA was related to that of abl 2-3 transcript as internal control. The threshold for the sensitivity of the Q-RT-PCR procedure was 16 bcr-abl mRNA molecule/microgram RNA. The lowest relative concentration was represented by detecting 1 bcr-abl mRNA molecule out of 12,600 abl 2-3 transcripts. The analysis of peripheral blood samples of 33 untreated patients indicated that the amount of chimera mRNA changes between 80 and 1,000,000 molecules per microgram RNA and this parameter correlated hardly (r = -44) with the tumour load. Data from blood samples of 48 treated patients indicated that this four order of magnitude difference in the expression persists in that patient population which exhibited on average major cytogenetic and also in those without any cytogenetic response. In the individual patients not only correlated changes of residual tumour mass and chimera expression, but mainly independent changes of these two parameters were observed.

In this paper, a patient is described who presented with peripheral blood and bone marrow features uncharacteristic of chronic granulocytic leukemia, which proved to be Philadelphia (Ph) chromosome-positive by metaphase and interphase cytogenetic analyses but lacked the p210 type of BCR/ABL fusion gene mRNA product by two different sensitive RT-PCR assays. In the course of the 32-month follow-up with a termination into a myeloblastic crisis, molecular investigations were performed four times. They indicated a constantly high rate of Ph positive cells and lack of BCR/ABL mRNA expression, except in the second investigation, when the patient showed reverse transcription polymerase chain reaction positivity with b3/a2 type of chimera, fusion gene mRNA expression, and a striking change in the bone marrow histology. Our findings might indicate that the dormant Ph chromosome state may exist not only at the primitive progenitor, but also at the entire peripheral blood cell compartment level.