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PubMed2001

Relapse of TEL-AML1--positive acute lymphoblastic leukemia in childhood: a matched-pair analysis.

PURPOSE: The aim of this study was to investigate whether, in relapsed childhood acute lymphoblastic leukemia (ALL), the frequent genetic feature of TEL-AML1 fusion resulting from the cryptic chromosomal translocation t(12;21)(p13;q22) is an independent risk factor. PATIENTS AND METHODS: A matched-pair analysis was performed within a homogeneous group of children with first relapse of BCR-ABL-negative B-cell precursor (BPC) ALL treated according to relapse trials ALL-Rezidiv (REZ) of the Berlin-Frankfurt-Münster Study Group. A total of 249 patients were eligible for this study: 53 (21%) were positive for TEL-AML1, and 196 (79%) were negative. Positive patients were matched for established most-significant prognostic determinants at relapse, time point, and site of relapse, as well as age and peripheral blast cell count at relapse. RESULTS: Fifty pairs matching the aforementioned criteria could be determined. The probabilities with SE of event-free survival and survival at 5 years for matched TEL-AML1 positives and negatives are 0.63 +/- 0.10 versus 0.38 +/- 0.10 (P =.09) and 0.82 +/- 0.09 versus 0.42 +/- 0.19 (P =.10), respectively. These results were confirmed by multivariate analysis, revealing an independent prognostic significance of time point and site of relapse (both P <.001) but not of TEL-AML1 expression (P =.09). CONCLUSION: TEL-AML1 expression does not constitute an independent risk factor in relapsed childhood BCP-ALL after matching for relevant prognostic parameters. It undoubtedly characterizes genetically an ALL entity associated with established favorable prognostic parameters. High-risk therapeutic procedures such as allogeneic SCT should be considered restrictively.

Adolescent↗
PubMed2001

The expression of ETV6/CBFA2 (TEL/AML1) is not sufficient for the transformation of hematopoietic cell lines in vitro or the induction of hematologic disease in vivo.

ETV6/CBFA2 (TEL/AML1) is the most frequent genetic abnormality associated with acute lymphoblastic leukemias in children, and is associated with a favorable prognosis. To investigate the influence of ETV6/CBFA2 on cellular transformation, the fusion gene was cloned into a murine ecotropic retroviral vector and transduced into IL-3-dependent Ba/F3 and 32Dcl.3 and IL-7-dependent IxN/2b murine hematopoietic cell lines. Different variants of ETV6/CBFA2, corresponding to CBFA2 alternatively spliced variants, and the reciprocal product CBFA2/ETV6, were stably expressed in each of these cell lines. However, although Western blot analysis demonstrated expression of each variant, none of the stable cell lines expressing CBFA2/ETV6 or the variants conferred factor-independent growth. We further investigated the effect of ETV6/CBFA2 expression in vivo by generating transgenic mice in which expression of the fusion was directed to lymphoid cells using the immunoglobulin heavy chain enhancer/promoter. Four founder mice were identified showing transmission and expression of the chimeric product. The mice were bred for five generations and followed for more than 24 months. The mice did not develop a malignant hematologic disorder, nor did they display histopathologic, morphologic, or immunophenotypic abnormalities, although ETV6/CBFA2 expression was confirmed in each line. We conclude that the expression of ETV6/CBFA2 alone is not sufficient for induction of growth factor independence in hematopoietic cell lines or hematologic disease in transgenic mice.

Animals↗
PubMed1999

TEL-AML1 fusion identifies a subset of children with standard risk acute lymphoblastic leukemia who have an excellent prognosis when treated with therapy that includes a single delayed intensification.

The Children's Cancer Group (CCG) found that children with moderate risk acute lymphoblastic leukemia (ALL) had an improved 5-year event-free survival (EFS) rate when treated with therapy that included a doubled delayed intensification (DDI) vs a single DI (SDI) phase. Because of increased toxicity with DDI, it is important to determine whether subgroups of children with ALL can be identified who have excellent outcomes with SDI therapy. TEL-AML1 fusion and hyperdiploid DNA content are present in the leukemic blasts of significant proportions of children with ALL and have been associated with an excellent prognosis. In this study, we retrospectively examined the impact of TEL-AML1 status and ploidy on treatment outcome in a cohort of 75 children with standard risk ALL treated at our institution between 1983 and 1993 with SDI therapy. TEL-AML1 fusion was present in 19/43 (44%) evaluable cases. Fifteen of 56 (27%) evaluable cases were classified as hyperdiploid based on a modal chromosome number of >/=51 and/or a DNA index of >/=1.16. The 7-year EFS was 81% for the 19 TEL-AML1-positive patients vs 54% for the 24 TEL-AML1-negative patients (P = 0.0264). In multivariate analyses, TEL-AML1-positive status was associated with a superior EFS (P = 0.02) even when the intial white blood count was included in the model. Overall survival (OS) at 7 years for TEL-AML1-positive patients was 100% vs 83% for TEL-AML1-negative patients (P = 0.0677). There were no differences in 7-year EFS or OS based on ploidy comparisons. These results underscore the need to examine closely the effects of treatment intensification on specific biologically defined subgroups of children with ALL.

Antineoplastic Agents↗
PubMed2004

TCRB gene rearrangements in childhood and adult precursor-B-ALL: frequency, applicability as MRD-PCR target, and stability between diagnosis and relapse.

Using the multiplex PCR tubes of the BIOMED-2 Concerted Action, TCRB gene rearrangements were detected in 35% of childhood (n=161) and adult (n=172) precursor-B-ALL patients (Vbeta-(Dbeta)-Jbeta in 25%; Dbeta-Jbeta in 15%). The presence of TCRB rearrangements showed a significant relation with age (highest frequency of 46% between 5 and 10 years of age) and the presence of TEL-AML1 transcripts, and was associated with relatively high frequencies of IGK-Kde, TCRG, and Vdelta2-Jalpha rearrangements. In 62 out of 65 patients with Southern blot-detected Vbeta-(Dbeta)-Jbeta and/or Dbeta-Jbeta rearrangements, at least one TCRB gene rearrangement was detected by PCR. Based on combined Southern blot and PCR analysis, oligoclonal TCRB gene rearrangements were observed in only 12% of patients. Analysis of paired diagnosis and relapse samples (n=26) showed that 20 out of 24 (83%) Vbeta-(Dbeta)-Jbeta rearrangements and eight out of 14 (57%) Dbeta-Jbeta rearrangements remained stable. Using real-time quantitative PCR, a quantitative range < or =10(-4) was obtained in 64% of TCRB gene rearrangements and in 86% of cases a sensitivity < or =10(-4) was obtained. In conclusion, TCRB gene rearrangements occur in 35% of precursor-B-ALL patients and are relatively stable and sensitive PCR targets for detection of minimal residual disease, particularly if this concerns complete Vbeta-(Dbeta)-Jbeta rearrangements.

Adult↗
PubMed2001

Interphase fluorescence in situ hybridization and spectral karyotyping reveals hidden genetic aberrations in children with acute lymphoblastic leukaemia and a normal banded karyotype.

Twenty-two cases of childhood acute lymphoblastic leukaemia (ALL) with normal G- or Q-banded karyotypes were studied by interphase fluorescence in situ hybridization (FISH) and spectral karyotyping. Probes detecting MLL, BCR/ABL and TEL/AML1 rearrangements were used for the interphase studies, along with centromere-specific probes from chromosomes 17 and X. In 10 patients (45%), previously undetected aberrations were demonstrable. Specific gene rearrangements and structural changes were found in six cases and numerical changes in five. Five of these aberrations have previously been reported to have an impact on prognosis. Three cases were massively hyperdiploid and, in one, the prognostically important BCR/ABL fusion was detected. In addition, a near-haploid karyotype with 27 chromosomes was found in one patient and TEL/AML1 rearrangements were detected in two cases. This study indicates that about half of childhood ALL cases with apparently normal karyotypes harbour genetic aberrations that may be detected using interphase FISH and spectral karyotyping.

Adolescent↗
PubMed2002

The TEL-AML1 real-time quantitative polymerase chain reaction (PCR) might replace the antigen receptor-based genomic PCR in clinical minimal residual disease studies in children with acute lymphoblastic leukaemia.

Prospective studies in children with B-precursor acute lymphoblastic leukaemia (ALL) have shown that polymerase chain reaction (PCR)-based detection of minimal residual disease (MRD) using immunoglobin (Ig) and T-cell receptor (TCR) gene rearrangements as targets can be used to identify patients with a high relapse risk. The disadvantage of this approach is that for each patient preferably two different targets have to be identified. The t(12;21)(p13;q22) with the TEL-AML1 fusion gene is present in approximately 25% of children with B-precursor ALL. In these patients, sensitive reverse transcription (RT)-PCR analysis of the TEL-AML1 fusion transcript might be a more simple and less laborious alternative approach. However, it is unknown how stable the mRNA is and whether the number of transcripts per leukaemic cell remains constant during follow-up. We investigated whether the MRD results obtained using RT-PCR of TEL-AML1 transcripts correlated with the clinically validated genomic PCR for Ig and TCR gene rearrangements. Therefore, we used real-time quantitative (RQ)-PCR analysis for both types of targets and assessed the MRD levels in 36 follow-up bone marrow samples (obtained during the first 1.5 years after diagnosis) from 13 patients with B-precursor ALL. In 34/36 bone marrow samples the Ig/TCR RQ-PCR and TEL-AML1 RQ-PCR revealed equal levels of MRD and these results had a strong correlation (P < 0.0001, R2 = 0.84). Therefore, we conclude that the TEL-AML1 RQ-PCR can, in principle, replace Ig/TCR RQ-PCR in B-precursor ALL with t(12;21).

Child↗
PubMed2003

Persistence of TEL-AML1 transcript in acute lymphoblastic leukemia in long-term remission.

BACKGROUND: It has recently been shown that t (12;21) (p13;q 22) is the most common molecular genetic abnormality in childhood acute lymphoblastic leukemia (ALL). We have analyzed this translocation in an attempt to evaluate its incidence and to monitor minimal residual disease (MRD) with t (12; 21) rearrangement by detection of TEL-AML1 transcript in patients with childhood ALL. PROCEDURE: All cryopreserved bone marrow samples were analyzed using a nested reverse transcription-polymerase chain reaction (RT-PCR) method. TEL-AML1 transcripts were searched for in 34 ALL patients, including six in relapse consecutively diagnosed at our institution between 1991 and 1997. RESULTS: TEL-AML1 transcripts were found in five (19%) of 27 patients with B precursor ALL. The patients with BCR-ABL, chromosome 11q23 rearrangement and T-ALL patients did not express TEL-AML1 transcripts. Moreover, MRD in five patients with TEL-AML1 transcripts were analyzed in serial samples. Although TEL-AML1 transcripts disappeared soon after the beginning of chemotherapy in three of the five patients, one patient continued to express them for up to 21 months without recurrence and remained in continuous complete remission for seven years after the cessation of chemotherapy. The remaining patient was admitted to our hospital after the second relapse but died following a failure to induce complete remission. CONCLUSION: For most patients, the presence of TEL-AML1 transcripts suggests excellent chemosensitivity and a favorable prognosis, but some patients with these transcripts have a different outcome. The present study suggests the possibility that a persistence of MRD is not necessarily related to a relapse of ALL with TEL-AML1 fusion. The prognostic significance of TEL-AML1 transcript remains controversial. Further studies are needed to evaluate the relation between the TEL-AML1 transcript and prognosis.

Child↗
PubMedDate not supplied

Prognostic significance of TEL/AML1 fusion transcript in childhood B-precursor acute lymphoblastic leukemia.

PURPOSE: A retrospective study was conducted to investigate the prognostic significance of TEL/AML1 fusion resulting from a cryptic t(12;21) in Japanese patients with childhood B-precursor acute lymphoblastic leukemia (ALL). MATERIALS AND METHODS: Leukemic samples from 144 children with newly diagnosed ALL (104 with CD10-positive B-precursor ALL, 11 with CD10-negative B-precursor ALL, 5 with B-ALL, and 24 with T-ALL) were analyzed by reverse-transcription polymerase chain reaction. RESULTS: The frequency of patients with TEL/AML1 was 16% (23 of 144) and all patients with TEL/AML1 also had CD10-positive B-precursor ALL. TEL/AML1 was not found in any samples from the patients with T-ALL, B-ALL, or CD10-negative B-precursor ALL. Among patients with CD10-positive B-precursor ALL, age, initial white blood cell count, and immunophenotype did not differ with TEL/AML1 positivity, although the patients were predominantly male (p < 0.01). Clinical outcomes of 94 patients treated with recent protocols were analyzed. Five of the 21 (23.8%) patients with TEL/AML1 relapsed and 4 of these relapsed > 24 months after diagnosis. Although the overall 5-year survival rate was better among patients with TEL/AML1 fusion transcript than among those without it (87.3 +/- 8.7% versus 75.9 +/- 5.8%, respectively), the 5-year disease-free survival (DFS) rates of patients with TEL/AML1 fusion transcript and those without it were similar (64.0 +/- 13.5% versus 69.1 +/- 6.3%, respectively). However, for 57 patients treated with the latest intensive protocol, the 4-year DFS rate was much higher for the patients with TEL/AML1 fusion transcript than for those without it (100.0% v.s. 69.6 +/- 8.4%, respectively, p = 0.1472). CONCLUSIONS: This study confirmed that TEL/AML1 gene fusion is the most common genetic event in pediatric ALL in Japan and is restricted to CD10-positive B-precursor ALL. Moreover, it was associated with an improved survival rate among patients treated with intensive therapy. Therefore, these data suggest that the patients with TEL/AML1 may not necessarily be candidates for less aggressive treatment.

Adolescent↗
PubMed2001

Breakage and fusion of the TEL (ETV6) gene in immature B lymphocytes induced by apoptogenic signals.

TEL-AML1 fusion resulting from the t(12;21)(p13;q22) is one of the most common genetic abnormalities in childhood acute lymphoblastic leukemia. Recent findings that site-specific cleavage of the MLL gene can be induced by chemotherapeutic agents such as topoisomerase-II inhibitors suggest that apoptogenic agents can cause chromosomal translocations in hematopoietic cells. This study demonstrates a possible relationship between exposure to apoptogenic stimuli, TEL breaks, and the formation of TEL-AML1 fusion in immature B lymphocytes. Short-term culture of immature B cell lines in the presence of apoptogenic stimuli such as serum starvation, etoposide, or salicylic acid induced double-strand breaks (DSBs) in intron 5 of the TEL gene and intron 1 of the AML1 gene. TEL-AML1 fusion transcripts were also identified by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis in cell lines treated by serum starvation or aminophylline. DSBs within the TEL gene were also associated with fusion to other unknown genes, presumably as a result of chromosomal translocation. We also examined 67 cord blood and 147 normal peripheral blood samples for the existence of in-frame TEL-AML1 fusion transcripts. One cord blood sample (1.5%) and 13 normal peripheral blood samples (8.8%) were positive as detected by nested RT-PCR. These data suggest that breakage and fusion of TEL and AML1 may be relatively common events and that sublethal apoptotic signals could play a role in initiating leukemogenesis via the promotion of DNA damage.

Aminophylline↗
PubMed1999

Precise developmental regulation of Ets family transcription factors during specification and commitment to the T cell lineage.

Ets family transcription factors control the expression of a large number of genes in hematopoietic cells. Here we show strikingly precise differential expression of a subset of these genes marking critical, early stages of mouse lymphocyte cell-type specification. Initially, the Ets family member factor Erg was identified during an arrayed cDNA library screen for genes encoding transcription factors expressed specifically during T cell lineage commitment. Multiparameter fluorescence-activated cell sorting for over a dozen cell surface markers was used to isolate 18 distinct primary-cell populations representing discrete T cell and B cell developmental stages, pluripotent lymphoid precursors, immature NK-like cells and myeloid hematopoietic cells. These populations were monitored for mRNA expression of the Erg, Ets-1, Ets-2, Fli-1, Tel, Elf-1, GABPalpha, PU.1 and Spi-B genes. The earliest stages in T cell differentiation show particularly dynamic Ets family gene regulation, with sharp transitions in expression correlating with specification and commitment events. Ets, Spi-B and PU.1 are expressed in these stages but not by later T-lineage cells. Erg is induced during T-lineage specification and then silenced permanently, after commitment, at the beta-selection checkpoint. Spi-B is transiently upregulated during commitment and then silenced at the same stage as Erg. T-lineage commitment itself is marked by repression of PU.1, a factor that regulates B-cell and myeloid genes. These results show that the set of Ets factors mobilized during T-lineage specification and commitment is different from the set that maintains T cell gene expression during thymocyte repertoire selection and in all classes of mature T cells.

Animals↗
PubMed2002

Preclinical validation of a monochrome real-time multiplex assay for translocations in childhood acute lymphoblastic leukemia.

PURPOSE: The purpose is to develop a real-time multiplex reverse transcription-PCR assay for detection and quantification of leukemia-specific chimeric transcripts that identify the genetic subgroups of acute lymphoblastic leukemias (ALLs) proposed by the WHO classification. EXPERIMENTAL DESIGN: Real-time multiplex assay for t(12;21), t(4;11), and t(1;19) with hypoxanthine phosphoribosyltransferase as internal standard used in tandem with a new real time quantitative-RT-PCR assay for the t(9;22). This new strategy was designed to yield an amplicon from each translocation with a distinct melting peak allowing dependable identification using only Sybr green I, without any need for expensive hybridization probes. RESULTS: We validated this method with 92 primary ALLs and identified 4 E2A-PBX1, 4 mBCR-ABL and 10 TEL-AML1. When compared with conventional RT-PCRs and Southern blot analyses, 100% concordance was obtained. During the course of these studies, we found marked variations in the levels of the TEL-AML1 transcripts in individual patients. We, therefore, extended the study to accurately and reproducibly determine TEL-AML1 mRNA levels in 47 additional patients with t(12;21). The results indicated that the level of expression of TEL-AML1 varied among individual patients, and it was independent of the WBC count. CONCLUSIONS: Our new real-time multiplex assay can be used for rapid, simple, and reliable classification of pediatric ALL. Its reproducible quantification results should also facilitate studies on minimal residual disease. The observed variation in TEL-AML1 transcript levels is of interest because it could reflect biological and/or clinical heterogeneity in the behavior of these leukemias.

Blotting, Southern↗
PubMed1997

Intensified therapy for infants with acute lymphoblastic leukemia: results from the Dana-Farber Cancer Institute Consortium.

BACKGROUND: Infants with acute lymphoblastic leukemia (ALL) have a very poor prognosis. Since 1985, we have intensified therapy for infants with ALL by including a month of high dose multiagent chemotherapy after remission induction. METHODS: Between 1985 and 1995, we treated 23 infants (age < 12 months). We compared the presenting characteristics and outcomes of these infants with the 11 infants treated on our protocols between 1973 and 1985, an era prior to the intensification of therapy. Available bone marrow samples from infants treated since 1985 were analyzed for the presence of MLL gene rearrangements by Southern blot analyses and for TEL-AML1 gene fusion by reverse transcriptase-polymerase chain reaction. RESULTS: With a median follow-up of 5.6 years, the 50-month event free survival (EFS) (+/- standard error) for the 23 infants was 54 +/- 11%, a significant improvement (P = 0.001) compared with the outcome for the 11 infants treated on our protocols prior to 1985 (EFS = 9 +/- 9%). Of the seven infants found to have a rearranged MLL gene, three (43%) remained in first complete remission. None of the nine infant bone marrow specimens tested had evidence of TEL-AML1 gene fusion. The intensified therapy was complicated by a high incidence of infections, including septicemia in 52% of patients and Pneumocystis carinii pneumonitis in 22% of patients. Late effects identified in the 13 long term survivors (median age, 6 years) included developmental delay and learning disabilities of varying severity (82% of evaluable patients), asymptomatic cataracts (67%), asymptomatic echocardiographic abnormalities (30%), obesity (27%), and short stature (18%). CONCLUSIONS: Intensification of therapy significantly improved the EFS of infants with ALL compared with previous, less intensive regimens and with the experience of other investigators. Future treatment for infants should attempt to improve efficacy while minimizing toxicity.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2002

The protein tyrosine kinase inhibitor SU5614 inhibits VEGF-induced endothelial cell sprouting and induces growth arrest and apoptosis by inhibition of c-kit in AML cells.

OBJECTIVE: Angiogenesis, the process of new blood vessel formation, is a critical process during growth and metastasis of solid tumors and might also represent a promising therapeutical target in patients with acute myeloid leukemia (AML). METHODS: In this study, we analyzed the expression of vascular endothelial growth factor receptors (VEGFR)-1/2 and its ligand VEGF in AML cell lines and characterized the inhibitory activity of the protein tyrosine kinase (PTK) inhibitor SU5614 on human endothelial and leukemic cells. RESULTS: Intracellular VEGF expression was detected in 9 of 10 leukemic cell lines. In contrast, VEGFR-1 and VEGFR-2 expression was restricted to 6 and 2 out of 10 cell lines, respectively. Although SU5614 was a potent inhibitor of the VEGF-induced endothelial cell sprouting in vitro, the sensitivity of leukemic cells toward the growth inhibitory activity of the compound was determined by the c-kit, but not by the VEGFR-1/2 expression. SU5614 induced growth arrest and apoptosis in c-kit-expressing Kasumi-1, UT-7, and M-07e cells and inhibited the stem cell factor (SCF)-induced tyrosine phosphorylation of c-kit. The sensitivity of Kasumi-1 cells towards the growth inhibitory activity of SU5614 was caused by an autocrine production of SCF, but not by transforming mutations of c-kit. CONCLUSIONS: Our data provide strong evidence that SU5614 has a dual mode of action, and by direct inhibition of c-kit in AML cells and by inhibition of VEGFR-2 in endothelial cells, it might represent a novel treatment option for patients with c-kit+ AML.

Acute Disease↗
PubMed1998

Fetal origins of the TEL-AML1 fusion gene in identical twins with leukemia.

The TEL (ETV6)-AML1 (CBFA2) gene fusion is the most common reciprocal chromosomal rearrangement in childhood cancer occurring in approximately 25% of the most predominant subtype of leukemia- common acute lymphoblastic leukemia. The TEL-AML1 genomic sequence has been characterized in a pair of monozygotic twins diagnosed at ages 3 years, 6 months and 4 years, 10 months with common acute lymphoblastic leukemia. The twin leukemic DNA shared the same unique (or clonotypic) but nonconstitutive TEL-AML1 fusion sequence. The most plausible explanation for this finding is a single cell origin of the TEL-AML fusion in one fetus in utero, probably as a leukemia-initiating mutation, followed by intraplacental metastasis of clonal progeny to the other twin. Clonal identity is further supported by the finding that the leukemic cells in the two twins shared an identical rearranged IGH allele. These data have implications for the etiology and natural history of childhood leukemia.

Amino Acid Sequence↗