Hilmar Quentmeier

Bio: Hilmar Quentmeier is an academic researcher from Leibniz Association. The author has contributed to research in topics: Myeloid leukemia & Leukemia. The author has an hindex of 38, co-authored 121 publications receiving 4597 citations. Previous affiliations of Hilmar Quentmeier include Deutsche Sammlung von Mikroorganismen und Zellkulturen & DSM.

Fusion of NUP214 to ABL1 on amplified episomes in T-cell acute lymphoblastic leukemia

Abstract: In T-cell acute lymphoblastic leukemia (T-ALL), transcription factors are known to be deregulated by chromosomal translocations, but mutations in protein tyrosine kinases have only rarely been identified. Here we describe the extrachromosomal (episomal) amplification of ABL1 in 5 of 90 (5.6%) individuals with T-ALL, an aberration that is not detectable by conventional cytogenetics. Molecular analyses delineated the amplicon as a 500-kb region from chromosome band 9q34, containing the oncogenes ABL1 and NUP214 (refs. 5,6). We identified a previously undescribed mechanism for activation of tyrosine kinases in cancer: the formation of episomes resulting in a fusion between NUP214 and ABL1. We detected the NUP214-ABL1 transcript in five individuals with the ABL1 amplification, in 5 of 85 (5.8%) additional individuals with T-ALL and in 3 of 22 T-ALL cell lines. The constitutively phosphorylated tyrosine kinase NUP214-ABL1 is sensitive to the tyrosine kinase inhibitor imatinib. The recurrent cryptic NUP214-ABL1 rearrangement is associated with increased HOX expression and deletion of CDKN2A, consistent with a multistep pathogenesis of T-ALL. NUP214-ABL1 expression defines a new subgroup of individuals with T-ALL who could benefit from treatment with imatinib.

FLT3 mutations in acute myeloid leukemia cell lines

Abstract: Internal tandem duplications (ITD) and D835 point mutations of the receptor tyrosine kinase (RTK) FLT3 are found in a high proportion of cases with acute myeloid leukemia (AML). These genetic aberrations may lead to the constitutive activation of the receptor, thus providing the molecular basis for a persisting growth stimulus. We have screened 69 AML-derived cell lines for FLT3 mutations. Four of these cell lines showed ITD of the FLT3 gene, none carried a D835 point mutation. Two cell lines (MUTZ-11 and MV4-11) expressed exclusively the mutated allele, the other two cell lines (MOLM-13 and PL-21) displayed a mutated and the wild-type version of the gene. Although mutationally activated FLT3 is supposed to substitute for the stimulatory signal of a growth factor, one of these cell lines (MUTZ-11) was strictly cytokine-dependent. FLT3 transcripts were found in all four cell lines, but the constitutively phosphorylated receptor protein was clearly detectable only in cell line MV4-11, possibly explaining why MUTZ-11 cells were growth-factor dependent. Thus, not all FLT3 ITD-positive cells express high levels of the active receptor protein, a finding that might be of relevance for a possible future application of a kinase inhibitor as therapeutic agent. It had been described that STAT-5 phosphorylation was part of the FLT3 signalling chain and that STAT-5 molecules were constitutively phosphorylated in FLT3 ITD-positive cells. Although we observed the constitutive phosphorylation of STAT-5 molecules in FLT3-mutant cells, FLT3 ligand (FL) did not induce STAT-5 phosphorylation in FLT3 wild-type cells. These results suggest that the signalling mechanisms of the mutated FL receptor differ at least to some extent from those conferred by wild-type FLT3. In conclusion, (1) not all cells with FLT3 ITD express significant amounts of the mutated receptor protein; (2) signals downstream from wild-type and mutant FLT3 receptors are not 100% identical; and (3) MV4-11 represents a model cell line for FLT3 ITD signalling.

Cloning of human thymic stromal lymphopoietin (TSLP) and signaling mechanisms leading to proliferation.

Abstract: Thymic stromal lymphopoietin (TSLP) is a novel cytokine that was found to promote the development of murine B cells in vitro. Here we describe the cloning and characterization of the human homologue of murine TSLP. This protein, which is expressed in a number of tissues including heart, liver and prostate, prevented apoptosis and stimulated growth of the human acute myeloid leukemia (AML)-derived cell line MUTZ-3. Anti-interleukin (IL)-7 receptor antibodies (Abs) neutralized this effect indicating that TSLP binds to at least part of the IL-7 receptor complex. TSLP induced phosphorylation of signal transducer and activator of transcription (STAT)-5. In contrast to IL-7, TSLP-triggered STAT-5 phosphorylation was not preceded by activation of janus kinase (JAK) 3. These findings would be in accordance with the notion, raised previously for the mouse system, that TSLP leads to STAT-5 phosphorylation by activating other kinases than the JAKs. Some other signaling pathways stimulated by many cytokines are not involved in TSLP activity; thus, TSLP did not stimulate activation of ERK1,2 and p70S6K. Furthermore, neutralizing Abs raised against cytokines known to stimulate the growth of MUTZ-3 cells did not inhibit the proliferative effects of TSLP, suggesting that TSLP-induced growth was a direct effect. In summary, we describe the cloning of human TSLP and its proliferative effects on a myeloid cell line. TSLP-induced proliferation is preceded by phosphorylation of STAT-5, but not of JAK 3.

Mutation of the Wilms’ Tumor 1 Gene Is a Poor Prognostic Factor Associated With Chemotherapy Resistance in Normal Karyotype Acute Myeloid Leukemia: The United Kingdom Medical Research Council Adult Leukaemia Working Party

Abstract: Purpose To determine the clinical relevance of Wilms’ tumor 1 (WT1) gene mutations in acute myeloid leukemia (AML) with normal karyotype (NK). Patients and Methods Exons 7 and 9 of WT1 were screened in samples from 470 young adult NK AMLs using a combination of direct sequencing and high-resolution capillary electrophoresis. Results Overall, 51 mutations were detected in 47 cases (10%): 46 frameshift mutations with insertion/deletion of one to 28 base pairs in exon 7 (n = 45) or exon 9 (n = 1), with a median mutant level of 45% (range, 8% to 86%), and five substitutions in exon 9: D396N (n = 3), H397Y (n = 1) and H397Q (n = 1). Patients with WT1 mutations had an inferior response to induction chemotherapy compared with wild-type cases (complete remission rate, 79% v 90%, odds ratio [OR] = 3.02; 95% CI, 1.17 to 7.82; P = .02), a higher rate of resistant disease (15% v 4%; OR = 9.33; 95% CI, 2.38 to 36.6; P = .001), an increased cumulative incidence of relapse (67% v 43%, hazard ratio [HR] = 3.02; 95% CI, 1...

Cell line OCI/AML3 bears exon-12 NPM gene mutation-A and cytoplasmic expression of nucleophosmin.

Abstract: We recently identified a new acute myeloid leukemia (AML) subtype characterized by mutations at exon-12 of the nucleophosmin (NPM) gene and aberrant cytoplasmic expression of NPM protein (NPMc+). NPMc+ AML accounts for about 35% of adult AML and it is associated with normal karyotype, wide morphological spectrum, CD34-negativity, high frequency of FLT3-ITD mutations and good response to induction therapy. In an attempt to identify a human cell line to serve as a model for the in vitro study of NPMc+ AML, we screened 79 myeloid cell lines for mutations at exon-12 of NPM. One of these cell lines, OCI/AML3, showed a TCTG duplication at exon-12 of NPM. This mutation corresponds to the type A, the NPM mutation most frequently observed in primary NPMc+ AML. OCI/AML3 cells also displayed typical phenotypic features of NPMc+ AML, that is, expression of macrophage markers and lack of CD34, and the immunocytochemical hallmark of this leukemia subtype, that is, the aberrant cytoplasmic expression of NPM. The OCI/AML3 cell line easily engrafts in NOD/SCID mice and maintains in the animals the typical features of NPMc+ AML, such as the NPM cytoplasmic expression. For all these reasons, the OCI/AML3 cell line represents a remarkable tool for biomolecular studies of NPMc+ AML.

Integrative Genomics Viewer

Abstract: Rapid improvements in sequencing and array-based platforms are resulting in a flood of diverse genome-wide data, including data from exome and whole-genome sequencing, epigenetic surveys, expression profiling of coding and noncoding RNAs, single nucleotide polymorphism (SNP) and copy number profiling, and functional assays. Analysis of these large, diverse data sets holds the promise of a more comprehensive understanding of the genome and its relation to human disease. Experienced and knowledgeable human review is an essential component of this process, complementing computational approaches. This calls for efficient and intuitive visualization tools able to scale to very large data sets and to flexibly integrate multiple data types, including clinical data. However, the sheer volume and scope of data pose a significant challenge to the development of such tools.