Karl Seeger

LAD-1/variant syndrome is caused by mutations in FERMT3

Leukocyte adhesion deficiency-1/variant (LAD1v) syndrome presents early in life and manifests by infections without pus formation in the presence of a leukocytosis combined with a Glanzmann-type bleeding disorder, resulting from a hematopoietic defect in integrin activation. In 7 consanguineous families, we previously established that this defect was not the result of defective Rap1 activation, as proposed by other investigators. In search of the genetic defect, we carried out homozygosity mapping in 3 of these patients, and a 13-Mb region on chromosome 11 was identified. All 7 LAD1v families share the same haplotype, in which 3 disease-associated sequence variants were identified: a putative splice site mutation in CALDAGGEF1 (encoding an exchange factor for Rap1), an intronic 1.8-kb deletion in NRXN2, and a premature stop codon (p.Arg509X) in FERMT3. Two other LAD1v patients were found to carry different stop codons in FERMT3 (p.Arg573X and p.Trp229X) and lacked the CALDAGGEF1 and NRXN2 mutations, providing convincing evidence that FERMT3 is the gene responsible for LAD1v. FERMT3 encodes kindlin-3 in hematopoietic cells, a protein present together with integrins in focal adhesions. Kindlin-3 protein expression was undetectable in the leukocytes and platelets of all patients tested. These results indicate that the LAD1v syndrome is caused by truncating mutations in FERMT3.

Oxygen-regulated expression of the RNA-binding proteins RBM3 and CIRP by a HIF-1-independent mechanism.

The transcriptional regulation of several dozen genes in response to low oxygen tension is mediated by hypoxia-inducible factor 1 (HIF-1), a heterodimeric protein composed of two subunits, HIF-1α and HIF-1β. In the HIF-1α-deficient human leukemic cell line, Z-33, exposed to mild (8% O2) or severe (1% O2) hypoxia, we found significant upregulation of two related heterogenous nuclear ribonucleoproteins, RNA-binding motif protein 3 (RBM3) and cold inducible RNA-binding protein (CIRP), which are highly conserved cold stress proteins with RNA-binding properties. Hypoxia also induced upregulation of RBM3 and CIRP in the murine HIF-1β-deficient cell line, Hepa-1 c4. In various HIF-1 competent cells, RBM3 and CIRP were induced by moderate hypothermia (32°C) but hypothermia was ineffective in increasing HIF-1α or vascular endothelial growth factor (VEGF), a known HIF-1 target. In contrast, iron chelators induced VEGF but not RBM3 or CIRP. The RBM3 and CIRP mRNA increase after hypoxia was inhibited by actinomycin-D, and in vitro nuclear run-on assays demonstrated specific increases in RBM3 and CIRP mRNA after hypoxia, which suggests that regulation takes place at the level of gene transcription. Hypoxia-induced RBM3 or CIRP transcription was inhibited by the respiratory chain inhibitors NaN3 and cyanide in a dose-dependent fashion. However, cells depleted of mitochondria were still able to upregulate RBM3 and CIRP in response to hypoxia. Thus, RBM3 and CIRP are adaptatively expressed in response to hypoxia by a mechanism that involves neither HIF-1 nor mitochondria.

Hypoxia upregulates the histone demethylase JMJD1A via HIF-1

The histone demethylase Jumonji domain containing 1A (JMJD1A) demethylates H3K9 residues and thereby transactivates distinct target genes. Investigating the effect of hypoxia on JMJD1A expression, we found increased JMJD1A mRNA in different organs of rats exposed to normobaric hypoxia (8% O(2)). Compared to adult samples, JMJD1A was increased in most tissues of human fetuses in whom oxygen supply is low compared to postnatal levels. Upregulation of JMJD1A mRNA and protein in cultured human cells exposed to hypoxia or iron scavengers in vitro was abrogated when hypoxia-inducible factor-1 (HIF-1) signaling was blocked by siRNAs. A single pivotal hypoxia responsive element (HRE) in the promoter of the human JMJD1A gene was identified that mediates JMJD1A upregulation by hypoxia, iron scavengers, and HIF-1. These findings demonstrate that JMJD1A can be stimulated by hypoxia both in vitro and in vivo involving binding of HIF-1 to a specific HRE in the JMJD1A promoter.

Mutations and Deletions of the TP53 Gene Predict Nonresponse to Treatment and Poor Outcome in First Relapse of Childhood Acute Lymphoblastic Leukemia

PURPOSE In the clinical management of children with relapsed acute lymphoblastic leukemia (ALL), treatment resistance remains a major challenge. Alterations of the TP53 gene are frequently associated with resistance to chemotherapy, but their significance in relapsed childhood ALL has remained controversial because of small studies. PATIENTS AND METHODS Therefore, we systematically studied 265 first-relapse patients enrolled in the German Acute Lymphoblastic Leukemia Relapse Berlin-Frankfurt-Mü nster 2002 (ALL-REZ BFM 2002) trial for sequence and copy number alterations of the TP53 gene by using direct sequencing and multiplex ligation-dependent probe amplification. RESULTS We observed copy number and sequence alterations of TP53 in 12.4% (27 of 218) of patients with B-cell precursor ALL and 6.4% (three of 47) of patients with T-cell ALL relapse. Backtracking to initial ALL in 23 matched samples revealed that 54% of all TP53 alterations were gained at relapse. Within B-cell precursor ALL, TP53 alterations were consistently associated with nonresponse to chemotherapy (P < .001) and poor event-free survival (P < .001) and overall survival rates (P = .002). TP53 alterations also had a significant impact on survival within intermediate-risk (S2) and high-risk (S3/S4) relapse patients (P = .007 and P = .019, respectively). This prognostic significance of TP53 alterations was confirmed in multivariate analysis. Besides their clinical impact, TP53 alterations were associated with a higher fraction of leukemic cells in S/G(2)-M phase of the cell cycle at relapse diagnosis. CONCLUSION Alterations of the TP53 gene are of particular importance in the relapse stage of childhood ALL, in which they independently predict high risk of treatment failure in a significant number of patients. Therefore, they will aid in future risk assessment of children with ALL relapse.

A novel flow cytometry-based platelet aggregation assay

The main function of platelets is to maintain normal hemostasis. Inefficient platelet production and/or defective platelet function results in bleeding disorders resulting from a wide range of genetic traits and acquired pathologies. Several platelet function tests have been developed for use in the clinic and in experimental animal models. In particular, platelet aggregation is routinely measured in an aggregometer, which requires normal platelet counts and significant blood sample volumes. For this reason, the analysis of thrombocytopenic patients, infants, and animal models is problematic. We have developed a novel flow cytometry test of platelet aggregation, in which 10- to 25-fold lower platelet counts or sample volumes can be used, either of platelet-rich plasma or whole blood from human subjects or mice. This setup can be applied to test in small assay volumes the influence of a variety of stimuli, drugs, and plasma factors, such as antibodies, on platelet aggregation. The presented principle stands as a novel promising tool, which allows analysis of platelet aggregation in thrombocytopenic patients or infants, and facilitates studies in platelets obtained from experimental animal models without the need of special devices but a flow cytometer.

Minimal residual disease after induction is the strongest predictor of prognosis in intermediate risk relapsed acute lymphoblastic leukaemia - long-term results of trial ALL-REZ BFM P95/96.

PURPOSE This blinded prospective study was performed to optimise the risk assessment of children with a late isolated, combined or an early combined bone marrow (BM) relapse of precursor B-cell acute lymphoblastic leukaemia (ALL). The aim was to develop a reliable tool to identify patients with an intermediate risk relapse who are in need of haematopoietic stem cell transplantation (HSCT). METHODS Included were 80 children and adolescents with first intermediate risk BM relapse of ALL recruited in trial ALL-REZ BFM P95/96. We assessed the prognostic value of minimal residual disease (MRD) after induction therapy quantified by PCR using leukaemia clone-specific T-cell receptor/immunoglobulin gene rearrangements. RESULTS Molecular good responders (MRD < 10(-3), n=46) had a probability of event-free survival (pEFS) at 10 years of 76% standard error (SE) ± 6% and a cumulative incidence of second relapse (CIR) at 10 years of 21% SE ± 6%; pEFS of molecular poor responders (MRD ≥ 10(-3), n=34) at 10 years was 18% SE ± 7% and CIR 61% SE ± 9% (p<0.001). Cox regression analysis revealed MRD after induction to be the strongest independent prognostic parameter with a 6.6-fold increased risk (95% confidence interval 3.3-13.5, p<0.001) for molecular poor responders to suffer a subsequent adverse event compared to good responders. CONCLUSION In patients with intermediate risk BM relapse of ALL, low MRD after induction is associated with an excellent long-term prognosis with conventional chemo-/radiotherapy whereas patients with insufficient response have an extremely poor prognosis. Therefore, in the subsequent trial ALL-REZ BFM 2002, MRD is used to allocate molecular good responders to conventional post-induction therapy and molecular poor responders to allogeneic HSCT.

The RNA-Binding Protein RBM3 Is Required for Cell Proliferation and Protects Against Serum Deprivation-Induced Cell Death

Hypoxia and other adverse conditions are commonly encountered by rapidly growing cells. The RNA-binding protein RBM3 (RNA-binding motif protein 3), which is transcriptionally induced by low temperature and hypoxia, has recently been implicated in survival of colon cancer cells by mechanisms involving cyclooxygenase-2 (COX-2) signaling. Immunohistochemically, we found strong RBM3 expression in a variety of malignant and proliferating tissues but low expression in resting and terminally differentiated cells. RBM3 expression in fibroblasts and human embryonal kidney (HEK293) cells subjected to serum deprivation or contact inhibition closely paralleled proliferation rates, assessed by real-time RT-PCR and immunoblotting. siRNA-mediated RBM3 knockdown reduced cell viability and finally led to cell death, which did not involve caspase-3-mediated apoptosis, cell cycle arrest, or COX-2 regulation. In contrast, RBM3 over-expression rescued cells from death under serum starvation. This was associated with increased translation rates, as measured by 14C serine and 3H phenylalanine incorporation. Together, RBM3 is a critical factor providing cellular survival advantages in an adverse microenvironment presumably by restoring translation efficacy.

Expression of Late Cell Cycle Genes and an Increased Proliferative Capacity Characterize Very Early Relapse of Childhood Acute Lymphoblastic Leukemia

Purpose: In childhood acute lymphoblastic leukemia (ALL), ∼25% of patients suffer from relapse. In recurrent disease, despite intensified therapy, overall cure rates of 40% remain unsatisfactory and survival rates are particularly poor in certain subgroups. The probability of long-term survival after relapse is predicted from well-established prognostic factors (i.e., time and site of relapse, immunophenotype, and minimal residual disease). However, the underlying biological determinants of these prognostic factors remain poorly understood. Experimental Design: Aiming at identifying molecular pathways associated with these clinically well-defined prognostic factors, we did gene expression profiling on 60 prospectively collected samples of first relapse patients enrolled on the relapse trial ALL-REZ BFM 2002 of the Berlin-Frankfurt-Münster study group. Results: We show here that patients with very early relapse of ALL are characterized by a distinctive gene expression pattern. We identified a set of 83 genes differentially expressed in very early relapsed ALL compared with late relapsed disease. The vast majority of genes were up-regulated and many were late cell cycle genes with a function in mitosis. In addition, samples from patients with very early relapse showed a significant increase in the percentage of S and G2-M phase cells and this correlated well with the expression level of cell cycle genes. Conclusions: Very early relapse of ALL is characterized by an increased proliferative capacity of leukemic blasts and up-regulated mitotic genes. The latter suggests that novel drugs, targeting late cell cycle proteins, might be beneficial for these patients that typically face a dismal prognosis.

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.

Outcome of children and adolescents with relapsed acute lymphoblastic leukaemia and non-response to salvage protocol therapy: A retrospective analysis of the ALL-REZ BFM Study Group

AIM OF THE STUDY Non-response (NR) to treatment of childhood relapsed acute lymphoblastic leukaemia (ALL) is an end-point of protocol therapy. Subsequent management has not yet been standardised. This study analyses different approaches after NR to aid optimising future strategies. PATIENTS AND METHODS Ninety-three children with NR to treatment according to ALL relapse-protocols of the Berlin/Frankfurt/Muenster (BFM) Study Group (03/1990-2006/1999) were retrospectively assigned to a curative (C: intensive polychemotherapies, stem cell transplantation (SCT); n=51), palliative (P: 1-2 antineoplastic agents; n=23) or supportive (S: no antineoplastic therapy; n=19) treatment approach. RESULTS Median survival after diagnosis of NR were 121 (C), 89 (P) and 42 (S) days, respectively (p<0.001). In cohort C, a complete remission (2ndCR) was obtained in 16/51 patients, among these 13 only after SCT, and nine children achieved partial remission. Ten of the 51 patients died from treatment-related complications, 39/51 from disease progression. Today, two patients are still in continuous CR after SCT. Adverse prognostic factors were overrepresented in the non-curative cohorts. Time-point of relapse and treatment after NR were independent predictors of survival duration. Most patients without antineoplastic treatment died at home, the majority of the others in the hospital. CONCLUSIONS Treatment after NR has been heterogeneous and customised. Therapies with curative intent are capable of inducing 2ndCR but associated with high treatment-related morbidity, -mortality and minimal survival. NR patients may, therefore, be ideal candidates for controlled phase I/II trials, thus offering them a chance to benefit from new drugs and promoting drug development for cohorts with better prognosis.