Three distinct domains in TEL-AML1 are required for transcriptional repression of the IL-3 promoter. (1/3678)

A cytogenetically cryptic (12;21) translocation is the most common molecular abnormality identified in childhood acute lymphoblastic leukemia (ALL), and it generates a chimeric TEL-AML1 protein. Fusion of the Helix-Loop-Helix (HLH) (also called the pointed) domain of TEL to AML1 has been suggested to convert AML1 from a transcriptional activator to a repressor. To define the structural features of this chimeric protein required for repression, we analysed the transcriptional activity of a series of TEL-AML1 mutants on the AML1-responsive interleukin-3 (IL-3) promoter, a potentially relevant gene target. Our results demonstrate that TEL-AML1 represses basal IL-3 promoter activity in lymphoid cells, and deletion mutant analysis identified three distinct domains of TEL-AML1 that are required for repression; the HLH (pointed) motif contained in the TEL portion of TEL-AML1, and both the runt homology domain (Rhd) and the 74 amino acids downstream of the Rhd that are present in the AML1 portion of the fusion protein. Although AML1B (and a shorter AML1 isoform, AML1A) have transcriptional activating activity on the IL-3 promoter, fusion of the AML1 gene to the TEL gene generates a repressor of IL-3 expression. Consistent with this activity, freshly isolated human ALL cells that contain TEL-AML1 do not express IL-3.  (+info)

Evidence of space-time clustering of childhood acute lymphoblastic leukaemia in Sweden. (2/3678)

We have examined 645 recorded cases of childhood acute lymphatic leukaemia (ALL) in Sweden during 1973-89 to identify space-time clustering by using the close-pair method of Knox. The records included date of birth and of diagnosis as well as addresses at birth and at diagnosis. There was a significant excess of case pairs close in date of birth and place of birth in the 5- to 15-year age group.  (+info)

Patterns of care and survival for adolescents and young adults with acute leukaemia--a population-based study. (3/3678)

We report a population-based study of patterns of care and survival for people with acute leukaemia diagnosed at age 15-29 years during 1984-94 in regions of England and Wales covered by specialist leukaemia registries. There were 879 patients: 417 with acute lymphoblastic leukaemia (ALL) and 462 with acute myeloid leukaemia (AML). For ALL, actuarial survival rates were 43% at 5 years after diagnosis and 37% at 10 years. Survival improved significantly between 1984-88 and 1989-94 for those aged 15-19 at diagnosis. Patients entered in national clinical trials and those not entered had similar survival rates. Survival rates were similar at teaching and non-teaching hospitals and at hospitals treating different numbers of study patients per year. For AML, survival rates were 42% at 5 years after diagnosis and 39% at 10 years. Survival improved significantly between 1984-88 and 1989-94. Patients entered in the Medical Research Council AML10 trial had a higher survival rate than those who were in the earlier AML9 trial. Survival did not vary with category of hospital. We conclude that survival has improved for adolescents and young adults with acute leukaemia but that there is at present no evidence that centralized treatment results in a survival benefit for patients in this age group.  (+info)

Susceptibility to childhood acute lymphoblastic leukemia: influence of CYP1A1, CYP2D6, GSTM1, and GSTT1 genetic polymorphisms. (4/3678)

Although acute lymphoblastic leukemia (ALL) is the most common childhood cancer, factors governing susceptibility to this disease have not yet been identified. As such, ALL offers a useful opportunity to examine the glutathione S-transferase and cytochrome P450 genes in determining susceptibility to pediatric cancers. Both enzymes are involved in carcinogen metabolism and have been shown to influence the risk a variety of solid tumors in adults. To determine whether these genes played a similar role in childhood leukemogenesis, we compared the allele frequencies of 177 childhood ALL patients and 304 controls for the CYP1A1, CYP2D6, GSTM1, and GSTT1 genes. We chose the French population of Quebec as our study population because of its relative genetic homogeneity. The GSTM1 null and CYP1A1*2A genotypes were both found to be significant predictors of ALL risk (odds ratio [OR] = 1.8). Those possessing both genotypes were at an even greater risk of developing the disease (OR = 3.3). None of the other alleles tested for proved to be significant indicators of ALL risk. Unexpectedly, girls carrying the CYP1A1*4 were significantly underrepresented in the ALL group (OR = 0.2), suggesting that a gender-specific protective role exists for this allele. These results suggest that the risk of ALL may indeed be associated with xenobiotics-metabolism, and thus with environmental exposures. Our findings may also explain, in part, why ALL is more prevalent among males than females.  (+info)

Prospective evaluation of the thrombotic risk in children with acute lymphoblastic leukemia carrying the MTHFR TT 677 genotype, the prothrombin G20210A variant, and further prothrombotic risk factors. (5/3678)

The reported incidence of thromboembolism in children with acute lymphoblastic leukemia (ALL) treated with L-asparaginase, vincristine, and prednisone varies from 2.4% to 11.5%. The present study was designed to prospectively evaluate the role of the TT677 methylenetetrahydrofolate reductase (MTHFR) genotype, the prothrombin G20210A mutation, the factor V G1691A mutation, deficiencies of protein C, protein S, antithrombin, and increased lipoprotein (a) concentrations in leukemic children treated according to the ALL-Berlin-Frankfurt-Muenster (BFM) 90/95 study protocols with respect to the onset of vascular events. Three hundred and one consecutive leukemic children were enrolled in this study. Fifty-five of these 301 subjects investigated had one established single prothrombotic risk factor: 20 children showed the TT677 MTHFR genotype; 5 showed the heterozygous prothrombin G20210A variant; 11 were carriers of the factor V G1691A mutation (heterozygous, n = 10; homozygous, n = 1); 4 showed familial protein C, 4 protein S, and 2 antithrombin type I deficiency; 9 patients were suffering from familially increased lipoprotein (a) [Lp(a)] concentrations (>30 mg/dL). In addition, combined prothrombotic defects were found in a further 10 patients: the FV mutation was combined with the prothrombin G20210A variant (n = 1), increased Lp(a) (n = 3), protein C deficiency (n = 1), and homozygosity for the C677T MTHFR gene mutation (n = 1). Lp(a) was combined with protein C deficiency (n = 2) and the MTHFR TT 677 genotype (n = 2). Two hundred eighty-nine of the 301 patients were available for thrombosis-free survival analysis. In 32 (11%) of these 289 patients venous thromboembolism occurred. The overall thrombosis-free survival in patients with at least one prothrombotic defect was significantly reduced compared with patients without a prothrombotic defect within the hemostatic system (P <.0001). In addition, a clear-cut positive correlation (P <.0001) was found between thrombosis and the use of central lines. However, because the prothrombotic defects diagnosed in the total childhood population studied were all found within the prevalences reported for healthy Caucasian individuals, the interaction between prothrombotic risk factors, ALL treatment, and further environmental factors is likely to cause thrombotic manifestations.  (+info)

Reduced folate carrier expression in acute lymphoblastic leukemia: a mechanism for ploidy but not lineage differences in methotrexate accumulation. (6/3678)

Methotrexate (MTX) is one of the most active and widely used agents for the treatment of acute lymphoblastic leukemia (ALL). To elucidate the mechanism for higher accumulation of MTX polyglutamates (MTX-PG) in hyperdiploid ALL and lower accumulation in T-lineage ALL, expression of the reduced folate carrier (RFC) was assessed by reverse transcription-polymerase chain reaction in ALL blasts isolated from newly diagnosed patients. RFC expression exhibited a 60-fold range among 29 children, with significantly higher expression in hyperdiploid B-lineage ALL (median, 11.3) compared with nonhyperdiploid ALL (median, 2.1; P <.0006), but no significant difference between nonhyperdiploid B-lineage and T-lineage ALL. Furthermore, mRNA levels of RFC (mapped by FISH to chromosome 21) were significantly related to chromosome 21 copy number (P =.0013), with the highest expression in hyperdiploid ALL blasts with 4 copies of chromosome 21. To assess the functional significance of gene copy number, MTX-PG accumulation was compared in ALL blasts isolated from 121 patients treated with either low-dose MTX (LDMTX; n = 60) or high-dose MTX (HDMTX; n = 61). After LDMTX, MTX-PG accumulation was highest in hyperdiploid B-lineage ALL with 4 copies of chromosome 21 (P =.011), but MTX-PG accumulation was not significantly related to chromosome 21 copy number after HDMTX (P =.24). These data show higher RFC expression as a mechanism for greater MTX accumulation in hyperdiploid B-lineage ALL and indicate that lineage differences in MTX-PG accumulation are not due to lower RFC expression in T-lineage ALL.  (+info)

Role of folylpolyglutamate synthetase and folylpolyglutamate hydrolase in methotrexate accumulation and polyglutamylation in childhood leukemia. (7/3678)

Inefficient polyglutamylation is a mechanism of resistance to methotrexate (MTX) in childhood T-lineage acute lymphoblastic leukemia (T-ALL) and in acute myeloid leukemia (AML) in comparison with childhood c/preB-ALL. We analyzed the profile of MTX polyglutamylation in childhood c/preB-ALL, T-ALL, and AML (n = 45, 15, and 14, respectively), the activity of the MTX-polyglutamate synthesizing enzyme folylpolyglutamate synthetase (FPGS) (n = 39, 11, and 19, respectively) and of the MTX-polyglutamate breakdown enzyme folylpolyglutamate hydrolase (FPGH) (n = 98, 25, and 34, respectively). MTX-Glu4-6 accumulation after 24 hours exposure to 1 micromol/L [3H]-MTX in vitro was lower in T-ALL (threefold) and AML (fourfold) compared with c/preB-ALL (P +info)

A requirement for protein kinase C inhibition for calcium-triggered apoptosis in acute lymphoblastic leukemia cells. (8/3678)

We have evaluated the cytotoxicities of the combinations of calcium mobilizers and PKC inhibitors against human acute lymphoblastic leukemia (ALL) cells. Here we report that calcium mobilizers alone or PKC inhibitors alone do not induce apoptosis in human ALL cells. However, the combinations of calcium mobilizers with potent inhibitors of PKC cause significant apoptosis in ALL cells. Our results provide experimental evidence that PKC blocks Ca2+-triggered apoptosis in human ALL cells. Thus, PKC inhibitors can be used to enhance the antileukemic activity of chemical or biological agents that trigger an apoptotic calcium signal in ALL cells. The exquisite sensitivity of ALL cells to calcium-dependent apoptosis in the presence of PKC inhibitors could provide the basis for new treatment programs against ALL.  (+info)