Leukemias harboring the ETV6-ABL1 fusion represent a rare subset of hematological malignancies with unfavorable outcomes. The constitutively active chimeric Etv6-Abl1 tyrosine kinase can be specifically inhibited by tyrosine kinase inhibitors (TKIs). Although TKIs represent an important therapeutic tool, so far, the mechanism underlying the potential TKI resistance in ETV6-ABL1-positive malignancies has not been studied in detail. To address this issue, we established a TKI-resistant ETV6-ABL1-positive leukemic cell line through long-term exposure to imatinib. ETV6-ABL1-dependent mechanisms (including fusion gene/protein mutation, amplification, enhanced expression or phosphorylation) and increased TKI efflux were excluded as potential causes of resistance. We showed that TKI effectively inhibited the Etv6-Abl1 kinase activity in resistant cells, and using short hairpin RNA (shRNA)-mediated silencing, we confirmed that the resistant cells became independent from the ETV6-ABL1 oncogene. Through analysis of the genomic and proteomic profiles of resistant cells, we identified an acquired mutation in the GNB1 gene, K89M, as the most likely cause of the resistance. We showed that cells harboring mutated GNB1 were capable of restoring signaling through the phosphoinositide-3-kinase (PI3K)/Akt/mTOR and mitogen-activated protein kinase (MAPK) pathways, whose activation is inhibited by TKI. This alternative GNB1K89M-mediated pro-survival signaling rendered ETV6-ABL1-positive leukemic cells resistant to TKI therapy. The mechanism of TKI resistance is independent of the targeted chimeric kinase and thus is potentially relevant not only to ETV6-ABL1-positive leukemias but also to a wider spectrum of malignancies treated by kinase inhibitors.

• MeSH
• chemorezistence účinky léků   MeSH
• fúzní onkogenní proteiny genetika   MeSH
• imatinib mesylát aplikace a dávkování   MeSH
• inhibitory proteinkinas aplikace a dávkování   MeSH
• leukemie farmakoterapie   genetika   patologie   MeSH
• lidé MeSH
• malá interferující RNA genetika   MeSH
• mutace MeSH
• nádorové buněčné linie MeSH
• proteiny vázající GTP - beta-podjednotky genetika   MeSH
• signální transdukce účinky léků   MeSH
• tyrosinkinasy genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fúzní onkogenní proteiny MeSH
• GNB1 protein, human MeSH Prohlížeč
• imatinib mesylát MeSH
• inhibitory proteinkinas MeSH
• malá interferující RNA MeSH
• proteiny vázající GTP - beta-podjednotky MeSH
• TEL-ABL fusion protein, human MeSH Prohlížeč
• tyrosinkinasy MeSH

Deletions in IKZF1 are found in ~15% of children with B-cell precursor acute lymphoblastic leukemia (BCP-ALL). There is strong evidence for the poor prognosis of IKZF1 deletions affecting exons 4-7 and exons 1-8, but evidence for the remaining 33% of cases harboring other variants of IKZF1 deletions is lacking. In an international multicenter study we analyzed the prognostic value of these rare variants in a case-control design. Each IKZF1-deleted case was matched to three IKZF1 wild-type controls based on cytogenetic subtype, treatment protocol, risk stratification arm, white blood cell count and age. Hazard ratios for the prognostic impact of rare IKZF1 deletions on event-free survival were calculated by matched pair Cox regression. Matched pair analysis for all 134 cases with rare IKZF1 deletions together revealed a poor prognosis (P<0.001) that was evident in each risk stratification arm. Rare variant types with the most unfavorable event-free survival were DEL 2-7 (P=0.03), DEL 2-8 (P=0.002) and DEL-Other (P<0.001). The prognosis of each type of rare variant was equal or worse compared with the well-known major DEL 4-7 and DEL 1-8 IKZF1 deletion variants. We therefore conclude that all variants of rare IKZF1 deletions are associated with an unfavorable prognosis in pediatric BCP-ALL.

• MeSH
• delece genu * MeSH
• dítě MeSH
• dospělí MeSH
• fúzní onkogenní proteiny analýza   MeSH
• kojenec MeSH
• lidé MeSH
• mezinárodní spolupráce MeSH
• mladiství MeSH
• pre-B-buněčná leukemie genetika   mortalita   MeSH
• předškolní dítě MeSH
• prognóza MeSH
• proporcionální rizikové modely MeSH
• protein PEBP2A2 analýza   MeSH
• transkripční faktor Ikaros genetika   MeSH
• Check Tag
• dítě MeSH
• dospělí MeSH
• kojenec MeSH
• lidé MeSH
• mladiství MeSH
• předškolní dítě MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fúzní onkogenní proteiny MeSH
• IKZF1 protein, human MeSH Prohlížeč
• protein PEBP2A2 MeSH
• TEL-AML1 fusion protein MeSH Prohlížeč
• transkripční faktor Ikaros MeSH

l-asparaginase (ASNase), a key component in the treatment of childhood acute lymphoblastic leukemia (ALL), hydrolyzes plasma asparagine and glutamine and thereby disturbs metabolic homeostasis of leukemic cells. The efficacy of such therapeutic strategy will depend on the capacity of cancer cells to adapt to the metabolic challenge, which could relate to the activation of compensatory metabolic routes. Therefore, we studied the impact of ASNase on the main metabolic pathways in leukemic cells. Treating leukemic cells with ASNase increased fatty-acid oxidation (FAO) and cell respiration and inhibited glycolysis. FAO, together with the decrease in protein translation and pyrimidine synthesis, was positively regulated through inhibition of the RagB-mTORC1 pathway, whereas the effect on glycolysis was RagB-mTORC1 independent. As FAO has been suggested to have a pro-survival function in leukemic cells, we tested its contribution to cell survival following ASNase treatment. Pharmacological inhibition of FAO significantly increased the sensitivity of ALL cells to ASNase. Moreover, constitutive activation of the mammalian target of rapamycin pathway increased apoptosis in leukemic cells treated with ASNase, but did not increase FAO. Our study uncovers a novel therapeutic option based on the combination of ASNase and FAO inhibitors.

• MeSH
• akutní lymfatická leukemie farmakoterapie   metabolismus   patologie   MeSH
• asparaginasa terapeutické užití   MeSH
• autofagie účinky léků   MeSH
• lidé MeSH
• mastné kyseliny metabolismus   MeSH
• mechanistické cílové místo rapamycinového komplexu 1 MeSH
• monomerní proteiny vázající GTP fyziologie   MeSH
• multiproteinové komplexy fyziologie   MeSH
• nádorové buněčné linie MeSH
• oxidace-redukce MeSH
• pyrimidiny biosyntéza   MeSH
• TOR serin-threoninkinasy fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• asparaginasa MeSH
• mastné kyseliny MeSH
• mechanistické cílové místo rapamycinového komplexu 1 MeSH
• monomerní proteiny vázající GTP MeSH
• multiproteinové komplexy MeSH
• pyrimidiny MeSH
• TOR serin-threoninkinasy MeSH

• MeSH
• akutní lymfatická leukemie genetika   patologie   MeSH
• delece genu * MeSH
• dítě MeSH
• filadelfský chromozom * MeSH
• jednonukleotidový polymorfismus genetika   MeSH
• kohortové studie MeSH
• lidé MeSH
• mutace genetika   MeSH
• nádorové biomarkery genetika   MeSH
• prognóza MeSH
• sekvenční analýza DNA MeSH
• transkripční faktor Ikaros genetika   MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• Publikační typ
• dopisy MeSH
• multicentrická studie MeSH
• práce podpořená grantem MeSH
• Názvy látek
• IKZF1 protein, human MeSH Prohlížeč
• nádorové biomarkery MeSH
• transkripční faktor Ikaros MeSH

Switches from the lymphoid to myeloid lineage during B-cell precursor acute lymphoblastic leukemia (BCP-ALL) treatment are considered rare and thus far have been detected in MLL-rearranged leukemia. Here, we describe a novel BCP-ALL subset, switching BCP-ALL or swALL, which demonstrated monocytosis early during treatment. Despite their monocytic phenotype, 'monocytoids' share immunoreceptor gene rearrangements with leukemic B lymphoblasts. All swALLs demonstrated BCP-ALL with CD2 positivity and no MLL alterations, and the proportion of swALLs cases among BCP-ALLs was unexpectedly high (4%). The upregulation of CEBPα and demethylation of the CEBPA gene were significant in blasts at diagnosis, prior to the time when most of the switching occurs. Intermediate stages between CD14(neg)CD19(pos)CD34(pos) B lymphoblasts and CD14(pos)CD19(neg)CD34(neg) 'monocytoids' were detected, and changes in the expression of PAX5, PU1, M-CSFR, GM-CSFR and other genes accompanied the switch. Alterations in the Ikaros and ERG genes were more frequent in swALL patients; however, both were altered in only a minority of swALLs. Moreover, switching could be recapitulated in vitro and in mouse xenografts. Although children with swALL respond slowly to initial therapy, risk-based ALL therapy appears the treatment of choice for swALL. SwALL shows that transdifferentiating into monocytic lineage is specifically associated with CEBPα changes and CD2 expression.

• MeSH
• antigeny CD2 imunologie   MeSH
• buněčný rodokmen MeSH
• dítě MeSH
• imunofenotypizace MeSH
• kohortové studie MeSH
• lidé MeSH
• mladiství MeSH
• monocyty patologie   MeSH
• multiplexová polymerázová řetězová reakce MeSH
• pre-B-buněčná leukemie imunologie   patologie   MeSH
• předškolní dítě MeSH
• prognóza MeSH
• reziduální nádor MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• předškolní dítě MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• validační studie MeSH
• Názvy látek
• antigeny CD2 MeSH

• MeSH
• akutní lymfatická leukemie genetika   MeSH
• antigeny CD2 metabolismus   MeSH
• dítě MeSH
• kojenec MeSH
• lidé MeSH
• předškolní dítě MeSH
• trans-aktivátory genetika   metabolismus   MeSH
• transkripční faktor Ikaros genetika   MeSH
• transkripční regulátor ERG MeSH
• Check Tag
• dítě MeSH
• kojenec MeSH
• lidé MeSH
• mužské pohlaví MeSH
• předškolní dítě MeSH
• ženské pohlaví MeSH
• Publikační typ
• dopisy MeSH
• Názvy látek
• antigeny CD2 MeSH
• ERG protein, human MeSH Prohlížeč
• IKZF1 protein, human MeSH Prohlížeč
• trans-aktivátory MeSH
• transkripční faktor Ikaros MeSH
• transkripční regulátor ERG MeSH

Translocation (12;21), the most frequent chromosomal aberration in childhood acute lymphoblastic leukemia, creates TEL/AML1 fusion gene. Resulting hybrid protein was shown to have a role in pre-leukemia establishment. To address its role for leukemic cell survival, we applied RNA interference to silence TEL/AML1 in leukemic cells. We designed and tested 11 different oligonucleotides targeting the TEL/AML1 fusion site. Using most efficient siRNAs, we achieved an average of 74-86% TEL/AML1 protein knockdown in REH and UOC-B6 leukemic cells, respectively. TEL/AML1 silencing neither decreased cell viability, nor induced apoptosis. On the contrary, it resulted in the modest but significant increase in the S phase fraction and in higher proliferation rate. Opposite effects on cell cycle distribution and proliferation were induced by AML1 silencing, thus, supporting our hypothesis that TEL/AML1 may block AML1-mediated promotion of G1/S progression through the cell cycle. In line with the lack of major effect on phenotype, we found no significant changes in clonogenic potential and global gene expression pattern upon TEL/AML1 depletion. Our data suggest that though TEL/AML1 is important for the (pre)leukemic clone development, it may be dispensable for leukemic cell survival and would not be a suitable target for gene-specific therapy.

• MeSH
• buněčné klony MeSH
• buněčný cyklus MeSH
• fúzní onkogenní proteiny genetika   fyziologie   MeSH
• leukemie patologie   MeSH
• lidé MeSH
• malá interferující RNA farmakologie   MeSH
• nádorové buněčné linie MeSH
• protein PEBP2A2 genetika   fyziologie   MeSH
• RNA interference * MeSH
• viabilita buněk * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fúzní onkogenní proteiny MeSH
• malá interferující RNA MeSH
• protein PEBP2A2 MeSH
• TEL-AML1 fusion protein MeSH Prohlížeč

Minimal residual disease (MRD) monitoring is an essential tool for risk group stratification in current treatment protocols for childhood acute lymphoblastic leukaemia (ALL). Although quantitative detection of clonal immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements is currently considered to be the standard method, leukaemia fusion genes provide other possible targets for MRD follow-up, as already demonstrated in TEL/AML1-positive ALLs. We analysed and compared MRD levels quantified by BCR/ABL transcript detection and by the standard Ig/TCR-based method in 218 bone marrow specimens from 17 children with BCR/ABL-positive ALL. We found only a limited overall correlation of MRD levels as assessed by the two methods (correlation coefficient R(2)=0.64). The correlation varied among patients from excellent (R(2)=0.99) to very poor (R(2)=0.17). Despite identical sensitivity of the approaches, 20% of the samples were negative by the Ig/TCR approach whereas positive by the BCR/ABL method. We show that multilineage involvement is at least partly responsible for the discrepancy. Moreover, our data demonstrate that BCR/ABL monitoring enables better and earlier prediction of relapse compared to the standard Ig/TCR methodology. We conclude that BCR/ABL-based MRD monitoring of childhood ALL is a clinically relevant tool and should be performed in parallel with the standard Ig/TCR follow-up.

• MeSH
• akutní lymfatická leukemie klasifikace   genetika   MeSH
• bcr-abl fúzové proteiny genetika   MeSH
• dítě MeSH
• genová přestavba T-lymfocytů genetika   MeSH
• geny pro imunoglobuliny genetika   MeSH
• indukce remise MeSH
• kultivované buňky MeSH
• lidé MeSH
• lokální recidiva nádoru genetika   MeSH
• messenger RNA genetika   metabolismus   MeSH
• mladiství MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• předškolní dítě MeSH
• prekurzorové B-lymfoidní buňky metabolismus   patologie   MeSH
• prognóza MeSH
• retrospektivní studie MeSH
• reziduální nádor genetika   MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• předškolní dítě MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bcr-abl fúzové proteiny MeSH
• messenger RNA MeSH