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J Zuna

Publications and source records attributed to J Zuna.

18 recordsLinked to original sources
PubMed2006

The MLL recombinome of acute leukemias.

Chromosomal rearrangements of the human MLL gene are a hallmark for aggressive (high-risk) pediatric, adult and therapy-associated acute leukemias. These patients need to be identified in order to subject these patients to appropriate therapy regimen. A recently developed long-distance inverse PCR method was applied to genomic DNA isolated from individual acute leukemia patients in order to identify chromosomal rearrangements of the human MLL gene. We present data of the molecular characterization of 414 samples obtained from 272 pediatric and 142 adult leukemia patients. The precise localization of genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) was determined and several new TPGs were identified. The combined data of our study and published data revealed a total of 87 different MLL rearrangements of which 51 TPGs are now characterized at the molecular level. Interestingly, the four most frequently found TPGs (AF4, AF9, ENL and AF10) encode nuclear proteins that are part of a protein network involved in histone H3K79 methylation. Thus, translocations of the MLL gene, by itself coding for a histone H3K4 methyltransferase, are presumably not randomly chosen, rather functionally selected.

Acute Disease↗
PubMed2002

Acute lymphoblastic leukemia incidence during socioeconomic transition: selective increase in children from 1 to 4 years.

Pre-school acute lymphoblastic leukemia (ALL) peak is consistent in developed but not in developing countries and its magnitude apparently correlates with the socioeconomic status. A population-based study describing ALL incidence during socioeconomic transition has been lacking. Central European post-communist countries (with very low foreign migration and centralized statistics) offer reliable data for the period before and during major socioeconomic changes. Population-based data on Czech ALL patients younger than 18 years were taken from two independent Czech national registries partially overlapping in time (1980-1998, n = 1236 and 1991-1999, n = 570). During the 1980s and 1990s, ALL incidence among children 1-4 years increased 1.5 times (P = 0.01). This increase was more prominent in females than in males (slopes 0.13 and 0.09, P values 0.03 and >0.05, respectively). No significant change was observed in other age groups (0, 5-9, 10-14, 15-17 years or all others combined). We discuss possible underlying socioeconomic factors including infant care and breast-feeding, hygiene, birth order, industry and pollution. Moreover, we try to pinpoint the immunophenotypic/molecular-genetic subsets of ALL that might be socioeconomically affected. Selective increase of ALL in children 1-4 years old provides epidemiological evidence that etiology and/or trigger mechanisms are different for a considerable proportion of these children and that these mechanisms are exogenous.

Age of Onset↗
PubMed2002

Real-time quantitative PCR detection of WT1 gene expression in children with AML: prognostic significance, correlation with disease status and residual disease detection by flow cytometry.

The clinical significance of WT1 gene expression at diagnosis and during therapy of AML has not yet been resolved. We analysed WT1 expression at presentation in an unselected group of 47 childhood AML patients using real-time quantitative reverse-transcription PCR. We also showed that within the first 30 h following aspiration RQ-RT-PCR results were not influenced by transportation time. We observed lower levels of WT1 transcript in AML M5 (P = 0.0015); no association was found between expression levels and sex, initial leukocyte count and karyotype-based prognostic groups. There was significant correlation between very low WT1 expression at presentation and excellent outcome (EFS P = 0.0014). Combined analysis of WT1 levels, three-colour flow cytometry residual disease detection and the course of the disease in 222 samples from 28 children with AML showed remarkable correlation. Fourteen patients expressed high WT1 levels at presentation. In eight of them, who suffered relapse or did not reach complete remission, dynamics of WT1 levels clearly correlated with the disease status and residual disease by flow cytometry. We conclude that very low WT1 levels at presentation represent a good prognostic factor and that RQ-RT-PCR-based analysis of WT1 expression is a promising and rapid approach for monitoring of MRD in approximately half of paediatric AML patients.

Acute Disease↗
PubMed2001

[Fluorescent in situ hybridization (FISH) in the diagnosis of acute childhood lymphatic leukemia (ALL)].

Classical cytogenetic analysis plays an important role in the diagnosis, classification, therapy monitoring and prognosis of patients with leukemia. Many recurrent cytogenetic abnormalities with major prognostic values have been described in childhood ALL. Hyperdiploidy and/or t(12;21) are associated with good prognosis, whereas t(9;22) and/or rearrangements of MLL gene correlate with poor outcome and therefore early detection of these abnormalities is very important. FISH can overcome some limitations of conventional cytogenetic and molecular-genetic analyses and due to high sensitivity specific chromosomal aberrations in mitoses and/or interphase nuclei can be detected. In the Center of Oncocytogenetics of the 3rd Medical Department for assessment of hyperdiploidy and structural rearrangements we use double-color FISH with centromeric and/or locus-specific probes and complex aberrations are ascertained by whole chromosome painting probes and multicolor FISH. Among 275 children with ALL examined during the last 8 years by different FISH methods we found seven patients with translocation t(9;22) and 14 patients with MLL rearrangements in bone marrow cells. Since 1988 we focus on detection of hyperdiploidy and/or t(12;21). High hyperdiploidy was found in 35 children, 10 of them had further complex rearrangements. Translocation t(12;21) was proved in 37 patients and complex rearrangements were found in 22 of them. FISH, cytogenetic and molecular-genetic analyses become obligatory for the first diagnostic examination as well as for monitoring of treatment effect in children with ALL.

Child↗
PubMed2001

[The role of TEL and AML1 genes in the pathogenesis of hematologic malignancies].

TEL and AML1 genes occur in a markedly high number of different aberrations in haematological malignancies. Besides the AML1, TEL is often fused to genes, which encod thyrosin-kinases. AML1 gene is a part of CBF transcription factor. AML1 can be altered in childhood acute lymphoblastic leukaemia (ALL) and also in a substantial number of acute myeloid leukaemias (most frequently as an AML1/ETO fusion). TEL/AML1 fusion gene (derived from t(12;21)(p13;q22) translocation) became recently one of the most important genetic aberrations in children with ALL. TEL/AML1 act presumably as dominant inhibitors of the second AML1 allele and thus they block transcription of genes dependent on CBF factor. Childhood ALL with TEL/AML1 hybrid gene is very frequent (approximately 22% of overall childhood ALL in the Czech Republic) and patients with this fusion form relatively homogenous group. These children are diagnosed mostly in pre-school age as a B cell precursor leukaemias and they have very good treatment results.

Animals↗
PubMed2000

Importance of using comparative genomic hybridization to improve detection of chromosomal changes in childhood acute lymphoblastic leukemia.

We used comparative genomic hybridization (CGH) and conventional cytogenetics (CC) to define chromosomal changes and to evaluate the usefulness of CGH in 65 patients having childhood acute lymphoblastic leukemia (ALL). Subsequently, fluorescence in situ hybridization (FISH) was used to evaluate the CGH and cytogenetic results. Comparative genomic hybridization revealed DNA copy number changes in 49 (75%) patients (including 7 patients with unsuccessful cytogenetics and 2 patients with normal karyotype). A total of 85 losses and 195 gains were detected. The most commonly gained chromosomes were 21 (35%), X (31%), 18 (27%), 10 (26%), 6 (25%), 17 (25%), 4 (23%), and 14 (22%). Losses were most frequently observed on chromosomes 9p (18%) and 12p (11%). Other losses were detected on chromosomes 13q (9%), 6q (9%), 7p (8%), and chromosome X (6%). Conventional cytogenetics revealed chromosomal changes in 53 (82%) patients. The employment of CGH and FISH together with CC analysis revealed chromosomal changes in 62 (95%) of the childhood ALL patients investigated. The CGH completed CC results in 36 patients; in 9 patients, the changes escaped detection without using CGH. The results of our study were compared to 6 other CGH studies previously reported. Our observations underline the benefits of supplementing routine cytogenetic investigation in childhood ALL by FISH and CGH, because small unbalanced changes may escape detection when conventional cytogenetics is the only diagnostic method used.

Adolescent↗
PubMed2000

[Monitoring minimal residual disease in pediatric patients with acute lymphoblastic leukemia].

The level of minimal residual disease is an important prognostic factor in childhood acute lymphoblastic leukaemia. The end of induction therapy is the most significant time-point for prediction of treatment outcome. Within a pilot study covered by the Paediatric Haematology Working Group in the Czech Republic 51 childhood patients were analysed at diagnosis of acute lymphoblastic leukaemia and at the end of induction using method based on detection of clonal rearrangements of immuno-receptor genes. The majority of tested patients (32/51, 63%) had a low or non-detectable levels of residual disease, a group of patients with the highest levels and thus the highest risk of relapse included 10% of patients (5/51). Within each of three risk groups one patient has relapsed so far. Therefore, the relapse rate in particular subgroups is 3% (1/32), 7% (1/14) and 20% (1/5) to date, respectively. The results are compared with these published by the BFM group (van Dongen et al., Lancet 1998). The pilot phase of a new BFM treatment protocols includes examination of residual disease for stratification of patients into the different risk groups.

Child↗
PubMed1999

[Detection of BCR/ABL, MLL/AF4 and TEL/AML1 hybrid genes and monitoring of minimal residual disease in pediatric patients with acute lymphoblastic leukemia].

BACKGROUND: The BCR/ABL and MLL/AF4 fusion genes--resulting from t(9;22)(q34;q11) and t(4;11)(q21;q23) translocations, respectively--are considered as a high risk prognostic factors in children with acute lymphoblastic leukaemia (ALL). Their presence in malignant cells indicates patient for the most intensive antileukaemic therapy regardless of the other criteria. In contrast, the most common non-random chromosomal aberration in paediatric ALL--translocation t(12;21)(q12;q22)--is associated with a favourable prognosis. The examination of these rearrangements is important for the stratification of patients to the risk groups and also provides the most sensitive and specific tool for minimal residual disease (MRD) follow-up. METHODS AND RESULTS: This study comprises 241 patients with ALL from Czech and Slovak Republics younger than 18 years at diagnosis. They were examined for presence of m-RNA of fusion genes BCR/ABL, MLL/AF4 and TEL/AML1 by reverse transcriptase-polymerase chain reaction (RT-PCR) method. Seven out of 197 (3.6%) carried MLL/AF4 fusion gene, but among infants it was 56% (5 out of 9). BCR/ABL positivity was found in 2.5% (7 out of 240) and TEL/AML1 in 21.7% (41 out of 189) cases. Event free survival (EFS) curves demonstrate the clinical impact of these hybrid genes on patients' prognosis. Moreover, we present the possibility of the monitoring of MRD levels in follow-up samples of these patients. CONCLUSIONS: All particular rearrangements were found only in a cohort of patients with B-precursor ALL (or hybrid leukaemia), which constitutes 85% of our group. Presence of BCR/ABL or MLL/AF4 fusion gene is associated with poor prognosis and is indispensable condition for correct stratification of patients to the risk groups according to treatment protocols. Hybrid gene TEL/AML1 defines subgroup of children with better prognosis and due to its high frequency provides us with a very useful tool for MRD detection.

Biomarkers, Tumor↗
PubMed1999

TEL/AML1 positivity in childhood ALL: average or better prognosis? Czech Paediatric Haematology Working Group.

The presence of TEL/AML1 fusion gene in childhood acute lymphoblastic leukaemia (ALL) defines a subgroup of patients with better than average outcome. However, the prognostic significance of this aberration has recently been disputed by the Berlin-Frankfurt-Münster (BFM) study group due to its relatively high incidence found in relapsed patients (19.6% and 21.9%, in two cohorts). In contrast, only four out of 45 (8.9%) unselected relapsed patients (all of whom had been treated according to BFM protocols) in the Czech Republic carry this fusion. From March 1995 to June 1998, 41 out of 190 (21.6%) newly diagnosed children with ALL were TEL/AML1-positive. There is a statistically significant difference between the incidence of TEL/AML1 fusion at diagnosis and at relapse within our group (P = 0.035). Interim analysis of the minimal residual disease (MRD) detection shows heterogeneity within the group of newly diagnosed TEL/AML1-positive leukaemias--10 out of 24 patients tested at the end of induction therapy had detectable levels of MRD. However, only one of these patients reached relapse-predictive level (10(-3)) of MRD. In conclusion, we corroborate low frequency of TEL/AML1 positivity among relapsed patients with ALL among Czech children who are treated by the BFM protocols. Moreover, we demonstrate different patterns of bone marrow clean-up in TEL/AML1-positive patients.

Adolescent↗
PubMed1998

Aberrant expression of KOR-SA3544 antigen in childhood acute lymphoblastic leukemia predicts TEL-AML1 negativity. The Pediatric Hematology Working Group in the Czech Republic.

The antigen KOR-SA3544 is physiologically expressed exclusively on granulocytes. Aberrant expression of KOR-SA3544 has been invariably found in BCR/ABL-positive acute lymphoblastic leukemia (ALL) and in some BCR/ABL-negative ALL. In an interim analysis of a prospective clinical and cytometric study data of 73 children with newly diagnosed or relapsed ALL with and without TEL/AML1 fusion are presented. KOR-SA3544 expression over 3% was detected in the majority of TEL/AML1-negative patients with newly diagnosed common or preB ALL (19 of 31) and not in TEL/AML1-positive patients (0 of 18, P < 0.0001). The level of expression of KOR-SA3544 was 0.02-90% (median 6.0%) and 0.03-2.4% (median 0.23%) in TEL/AML1-negative and TEL/AML1-positive patients, respectively. All five newly diagnosed patients with DNA index > or =1.16 and <1.6 exhibited high levels of KOR-SA3544 expression. Membrane expression of CD79a was found to correlate with TEL/AML1 negativity, although less significantly than KOR-SA3544 (P = 0.03). Furthermore, our data confirm that TEL/AML1 positivity correlates with non-hyperdiploidy and low presenting age. In conclusion, KOR-SA3544 correlated strongly with TEL/AML1 negativity, it was a better predictor of TEL/AML1 status than other factors tested and was found at high levels in hyperdiploidy. In combination with age, KOR-SA3544 predicted TEL/AML1 status in 86% newly diagnosed preB/cALL patients.

Age Factors↗
PubMed1998

[Detection of monoclonality in childhood lymphoma with the polymerase chain reaction].

We studied monoclonality of tumour cells by polymerase chain reaction (PCR) in paediatric lymphomas. In B-lymphomas we detected monoclonal rearrangement of the immunoglobulin of the T-cell receptor delta and gamma chain (TCR, TCR-delta, TCR-gamma) by an analogous way. We examined a group of 37 paediatric patients with lymphomas (26 with B-lymphomas and 11 with T-lymphomas). Monoclonal gene rearrangement was found in 34 cases, i.e. the method used in this study proved to be successful in 92% of cases. We confirmed our results by correlation with histologic and immunohistologic diagnoses. The method may be used as a complementary diagnostic tool in differential diagnosis of lymphoma versus non-neoplastic proliferation of lymphatic tissue, in distinction between B- and T-lymphomas, and to separate lymphomas and other malignancies. Beside the pure diagnostic usage we perceive the main importance of the method in monitoring minimal residual disease (MRD), because amplified products of PCR may be sequenced and used for preparing tumour specific primers and probes.

Child↗