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J Trka

Publications and source records attributed to J Trka.

At least 19 recordsLinked to original sources
PubMed2006

Wilms' tumor gene 1 (WT1) expression in childhood acute lymphoblastic leukemia: a wide range of WT1 expression levels, its impact on prognosis and minimal residual disease monitoring.

Wilms' tumor gene 1 (WT1) is overexpressed in the majority (70-90%) of acute leukemias and has been identified as an independent adverse prognostic factor, a convenient minimal residual disease (MRD) marker and potential therapeutic target in acute leukemia. We examined WT1 expression patterns in childhood acute lymphoblastic leukemia (ALL), where its clinical implication remains unclear. Using a real-time quantitative PCR designed according to Europe Against Cancer Program recommendations, we evaluated WT1 expression in 125 consecutively enrolled patients with childhood ALL (106 BCP-ALL, 19 T-ALL) and compared it with physiologic WT1 expression in normal and regenerating bone marrow (BM). In childhood B-cell precursor (BCP)-ALL, we detected a wide range of WT1 levels (5 logs) with a median WT1 expression close to that of normal BM. WT1 expression in childhood T-ALL was significantly higher than in BCP-ALL (P<0.001). Patients with MLL-AF4 translocation showed high WT1 overexpression (P<0.01) compared to patients with other or no chromosomal aberrations. Older children (> or =10 years) expressed higher WT1 levels than children under 10 years of age (P<0.001), while there was no difference in WT1 expression in patients with peripheral blood leukocyte count (WBC) > or =50 x 10(9)/l and lower. Analysis of relapsed cases (14/125) indicated that an abnormal increase or decrease in WT1 expression was associated with a significantly increased risk of relapse (P=0.0006), and this prognostic impact of WT1 was independent of other main risk factors (P=0.0012). In summary, our study suggests that WT1 expression in childhood ALL is very variable and much lower than in AML or adult ALL. WT1, thus, will not be a useful marker for MRD detection in childhood ALL, however, it does represent a potential independent risk factor in childhood ALL. Interestingly, a proportion of childhood ALL patients express WT1 at levels below the normal physiological BM WT1 expression, and this reduced WT1 expression appears to be associated with a higher risk of relapse.

Adolescent↗
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↗
PubMed2006

[Frequency view on genome changes testing].

Laboratories dealing with human genome, both inherited and acquired changes, dispose with similar methods and technology. The spectrum of genetic tests is relatively broad and the number of mutations or variants tested differs substantially. Also the number of examinations carried out in individual laboratories varies. Data presented in the tables come from the year 2004 and indicate the number of examinations requested and number of positive results. Many laboratories mentioned in the registry CZDDNAL (http://www.uhkt.cz/lab_a_vysetreni/nr lab_dna_diag/dna_lab_db) perform the same tests but there is also a great number of tests carried out by only one laboratory. Reasons of the request, cost-effectiveness and clinical utility of genetic testing is being discussed.

Gene Frequency↗
PubMed2004

Upregulation of asparagine synthetase fails to avert cell cycle arrest induced by L-asparaginase in TEL/AML1-positive leukaemic cells.

L-Asparaginase is a standard component in chemotherapy of childhood acute lymphoblastic leukaemia (ALL). Leukaemic cells carrying TEL/AML1 fusion gene are more sensitive to treatment with L-asparaginase compared to other subtypes of ALL. We demonstrate in vitro the prolonged growth suppression of TEL/AML1[+] cells compared to TEL/AML1[-] leukaemic cells after L-asparaginase treatment simulating treatment protocol. Cell cycle analysis revealed TEL/AML1[+] cells to accumulate in G1/G0 phase (81-98%) compared to TEL/AML1[-] cells (47-60%). Quantitative analysis of asparagine synthetase (AsnS) expression showed the ability of TEL/AML1[+] cells to increase AsnS mRNA levels after L-asparaginase treatment to the same extent as TEL/AML1[-] leukaemic and nonleukaemic lymphoid cells. We hypothesise that TEL/AML1[+] cells are unable to progress into the S phase of cell cycle under nutrition stress caused by L-asparaginase, despite the ability of AsnS upregulation. Significantly higher expression of AsnS was found in untreated leukaemic cells from children with TEL/AML1[+] ALL (n=20) in comparison with the group of age-matched children with ALL bearing no known fusion gene (n=25; P=0.0043). Interestingly, none of the TEL/AML1[+] patients with high AsnS level relapsed, whereas 10/15 patients with AsnS below median relapsed (P=0.00028). Therefore, high AsnS levels in TEL/AML1[+] patients correlate with better prognosis, possibly reflecting the stretched metabolic demand of the lymphoblast.

Asparaginase↗
PubMed2003

[Improved results in children with acute lymphoblastic leukemia treated with the ALL-BFM 90 protocol in the Czech Republic].

BACKGROUND: Prognosis of children with acute lymphoblastic leukaemia (ALL)--the most common cancer in childhood, has improved remarkably over the last 40 years. The authors report the treatment outcome in children with ALL cured according to ALL-BFM 90 Study protocol in the Czech Republic during the first half of nineties. METHODS AND RESULTS: Children aged 0-18 years were included into the study in 10 centers between 1990 to 1996. Patients were classified into standard-risk (SR), medium-risk (MR) and high-risk (HR) group according to initial leukaemic burden, early treatment response, and genotype of leukaemia. Duration of the chemotherapy was two years. Treatment results were evaluated in 352 children. With a median follow-up of 7.3 years, event-free-survival (EFS) was 71.3% and overall survival 76.4%. EFS was 80.3%, 74% and 28.2% in SR, MR and HR group, respectively. Relapse was diagnosed in 17.8% of the patients. CONCLUSIONS: The treatment outcome of children with ALL improved significantly (p = 0.0045) compared to the previous study ALL-BFM 83 (EFS 62%). These results are comparable to those achieved by leading leukaemia study groups in the world.

Adolescent↗
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↗
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↗