Complex MLL rearrangements in t(4;11) leukemia patients with absent AF4.MLL fusion allele.

The human mixed lineage leukemia (MLL) gene is frequently involved in genetic rearrangements with more than 55 different translocation partner genes, all associated with acute leukemia. Reciprocal chromosomal translocations generate two MLL fusion alleles, where 5'- and 3'-portions of MLL are fused to gene segments of given fusion partners. In case of t(4;11) patients, about 80% of all patients exhibit both reciprocal fusion alleles, MLL.AF4 and AF4.MLL, respectively. By contrast, 20% of all t(4;11) patients seem to encode only the MLL.AF4 fusion allele. Here, we analyzed these 'MLL.AF4(+)/AF4.MLL(-)' patients at the genomic DNA level to unravel their genetic situation. Cryptic translocations and three-way translocations were found in this group of t(4;11) patients. Reciprocal MLL fusions with novel translocation partner genes, for example NF-KB1 and RABGAP1L, were identified and actively transcribed in leukemic cells. In other patients, the reciprocal 3'-MLL gene segment was fused out-of-frame to PBX1, ELF2, DSCAML1 and FXYD6. The latter rearrangements caused haploinsufficiency of genes that are normally expressed in hematopoietic cells. Finally, patients were identified that encode only solitary 3'-MLL gene segments on the reciprocal allele. Based on these data, we propose that all t(4;11) patients exhibit reciprocal MLL alleles, but due to the individual recombination events, provide different pathological disease mechanisms.

Immunobiological diversity in infant acute lymphoblastic leukemia is related to the occurrence and type of MLL gene rearrangement.

The aim of this study was to identify immunobiological subgroups in 133 infant acute lymphoblastic leukemia (ALL) cases as assessed by their immunophenotype, immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangement pattern, and the presence of mixed lineage leukemia (MLL) rearrangements. About 70% of cases showed the pro-B-ALL immunophenotype, whereas the remaining cases were common ALL and pre-B-ALL. MLL translocations were found in 79% of infants, involving MLL-AF4 (41%), MLL-ENL (18%), MLL-AF9 (11%) or another MLL partner gene (10%). Detailed analysis of Ig/TCR rearrangement patterns revealed IGH, IGK and IGL rearrangements in 91, 21 and 13% of infants, respectively. Cross-lineage TCRD, TCRG and TCRB rearrangements were found in 46, 17 and 10% of cases, respectively. As compared to childhood precursor-B-ALL, Ig/TCR rearrangements in infant ALL were less frequent and more oligoclonal. MLL-AF4 and MLL-ENL-positive infants demonstrated immature rearrangements, whereas in MLL-AF9-positive leukemias more mature rearrangements predominated. The immature Ig/TCR pattern in infant ALL correlated with young age at diagnosis, CD10 negativity and predominantly with the presence and the type of MLL translocation. The high frequency of immature and oligoclonal Ig/TCR rearrangements is probably caused by early (prenatal) oncogenic transformation in immature B-lineage progenitor cells with germline Ig/TCR genes combined with a short latency period.

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.

Preeclampsia and its interaction with common variants in thrombophilia genes.

Recently, it has been proposed that abnormalities in coagulation and fibrinolysis contribute to the development of preeclampsia by increasing the thrombotic tendency. This hypothesis was tested in women who have had preeclampsia (cases) compared with matched controls. Polymorphisms in the thrombophilia genes [plasminogen activator inhibitor type 1 [PAI-1 -675(4G/5G)], thrombin activatable fibrinolysis inhibitor (TAFI -438G/A and 1040C/T), methylenetetrahydrofolate reductase (MTHFR 677C/T), factor V (FV Leiden R/Q506), prothrombin (FII 20210G/A) and factor XIIIA (FXIIIA V/L34)] were determined in 157 women with preeclampsia and 157 women with uncomplicated pregnancy. The associated risk of preeclampsia was analyzed using logistic regression methods. The frequency distributions of the genotypes of these six polymorphisms in thrombophilia genes were similar in the case and control groups. We found no differences in the prevalence of genetic risk factors of thrombosis in women with preeclampsia compared with controls, which makes it unlikely that these polymorphisms are risk factors for preeclampsia.

Prognostic significance of minimal residual disease in infants with acute lymphoblastic leukemia treated within the Interfant-99 protocol.

Acute lymphoblastic leukemia (ALL) in infants younger than 1 year is a rare but relatively homogeneous disease ( approximately 80% MLL gene rearranged, approximately 70% CD10-negative) when compared with childhood and adult ALL. Several studies in children and adults with ALL have shown that minimal residual disease (MRD) status is a strong and independent prognostic factor. We therefore evaluated the prognostic significance of MRD in infant ALL. Ninety-nine infant patients treated according to the Interfant-99 protocol were included in this study. MRD was analyzed by real-time quantitative PCR analysis of rearranged immunoglobulin genes, T-cell receptor genes and MLL genes at various time points (TP) during therapy. Higher MRD levels at the end of induction (TP2) and consolidation (TP3) were significantly associated with lower disease-free survival. Combined MRD information at TP2 and TP3 allowed recognition of three patients groups that significantly differed in outcome. All MRD-high-risk patients (MRD levels > or =10(-4) at TP3; 26% of patients) relapsed. MRD-low-risk patients (MRD level <10(-4) at both TP2 and TP3) constituted 44% of patients and showed a relapse-rate of only 13%, whereas remaining patients (MRD-medium-risk patients; 30% of patients) had a relapse rate of 31%. Comparison between the current Interfant-06 stratification at diagnosis and the here presented MRD-based stratification showed that both stratifications recognized different subgroups of patients. These data indicate that MRD diagnostics has added value for recognition of risk groups in infant ALL and that MRD diagnostics can be used for treatment intervention in infant ALL as well.

Interleukin 10-2849AA genotype protects against pre-eclampsia.

Recently, it has been described that human fertility is associated with the interleukin 10 (IL10) -2849 AA genotype. Pre-eclampsia is the most common pregnancy-specific complication. In the pathogenesis of pre-eclampsia, IL10 may affect maternal intravascular inflammation as well as endothelial dysfunction. Therefore, we tested the hypothesis that pre-eclampsia is associated with genetic variation in the IL10 promoter region in a case-control study for pre-eclampsia. Women homozygous for the IL10 -2849A allele have a threefold reduced risk for pre-eclampsia compared to controls (odds ratio 0.29; 95% CI 0.10-0.83). No differences in genotype frequency were found for polymorphisms in the IL10 promoter region at positions -1082, -819 and -592. This suggests that there is a genetically determined mechanism which protects the mother against pre-eclampsia, as reflected in the lower frequency of the IL10 -2849AA genotype in pre-eclamptic women.