Biomedical subjects

Benedikt Brors

Publications and source records attributed to Benedikt Brors.

23 records · Page 2Linked to original sources

PubMed2005

Distinct gene expression patterns associated with FLT3- and NRAS-activating mutations in acute myeloid leukemia with normal karyotype.

In acute myeloid leukemia (AML), constitutive activation of the FLT3 receptor tyrosine kinase, either by internal tandem duplications (FLT3-ITD) of the juxtamembrane region or by point mutations in the second tyrosine kinase domain (FLT3-TKD), as well as point mutations of the NRAS gene (NRAS-PM) are among the most frequent somatic gene mutations. To elucidate whether these mutations cause aberrant signal transduction in AML, we used gene expression profiling in a series of 110 newly diagnosed AML patients with normal karyotype. The different algorithms used for data analysis revealed highly concordant sets of genes, indicating that the identified gene signatures are specific for each analysed subgroup. Whereas samples with FLT3-ITD and FLT3-TKD could be separated with up to 100% accuracy, this did not apply for NRAS-PM and wild-type samples, suggesting that only FLT3-ITD and FLT3-TKD are associated with an apparent signature in AML. The set of discriminating genes included several known genes, which are involved in cell cycle control (CDC14A, WEE1), gene transcription (HOXB5, FOXA1), and signal transduction (SMG1). In conclusion, we showed that unique gene expression patterns can be correlated with FLT3-ITD and FLT3-TKD. This might lead to the identification of further pathogenetic relevant candidate genes particularly in AML with normal karyotype.

Gene Expression Regulation, Neoplastic↗

PubMed2004

Pathways of urothelial cancer progression suggested by Bayesian network analysis of allelotyping data.

Urothelial cancers of the bladder (UC) comprise biologically heterogeneous group of tumors and display complex genetic alterations. Several genetic changes have been analyzed in detail and some of them are associated with the development and progression of UCs. Only a few studies, however, are focused on identifying the order in which the aberrations may appear during UC tumorigenesis. We have analyzed 123 papillary UCs of the bladder by microsatellites for each of the chromosomal regions that have been suggested to be specifically involved in this type of tumor. We used Bayesian network modeling that enables to uncover multivariate probabilistic dependencies between variables. This methodology applied to LOH data allowed us to discover patterns of losses in UCs. Exploiting the mechanism of probabilistic reasoning in Bayesian networks we suggest primary and secondary events in tumor pathogenesis and reconstruct the possible flow of progression of allelic changes. Losses of chromosome 9p and 9q were found to be the primary events. Losses of 8p and 17p are important events leading to progression of tumor cell clones. The loss of 17p occurs when both abnormalities of chromosome 9 and 8p are already present. There are chromosomal losses related to 8p (1q, 18q, 10q) and some losses like 5q/5p were associated with 17p, leading to the hypothesis of different genetic pathways of UC progression. The abnormalities of chromosome regions 13q, 16q, 6q, 14q, 3p are suggested to be late events being accumulated during the progression of cancer. Although some genetic changes were associated only with the 8p pathway, most secondary genetic changes appear in both pathways. Supplementary material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html.

Alleles↗

PubMed2004

Medullary epithelial cells of the human thymus express a highly diverse selection of tissue-specific genes colocalized in chromosomal clusters.

Promiscuous expression of tissue-specific self-antigens in the thymus imposes T cell tolerance and protects from autoimmune diseases, as shown in animal studies. Analysis of promiscuous gene expression in purified stromal cells of the human thymus at the single and global gene level documents the species conservation of this phenomenon. Medullary thymic epithelial cells overexpress a highly diverse set of genes (>400) including many tissue-specific antigens, disease-associated autoantigens, and cancer-germline genes. Although there are no apparent structural or functional commonalities among these genes and their products, they cluster along chromosomes. These findings have implications for human autoimmune diseases, immuno-therapy of tumors, and the understanding of the nature of this unorthodox regulation of gene expression.

Animals↗

PubMed2002

Acute myeloid leukemias with reciprocal rearrangements can be distinguished by specific gene expression profiles.

Acute myeloid leukemia (AML) is a heterogeneous group of genetically defined diseases. Their classification is important with regard to prognosis and treatment. We performed microarray analyses for gene expression profiling on bone marrow samples of 37 patients with newly diagnosed AML. All cases had either of the distinct subtypes AML M2 with t(8;21), AML M3 or M3v with t(15;17), or AML M4eo with inv(16). Diagnosis was established by cytomorphology, cytogenetics, fluorescence in situ hybridization, and reverse transcriptase-PCR in every sample. By using two different strategies for microarray data analyses, this study revealed a unique correlation between AML-specific cytogenetic aberrations and gene expression profiles.

Acute Disease↗

PubMed2002

Microarray data warehouse allowing for inclusion of experiment annotations in statistical analysis.

MOTIVATION: Microarray technology provides access to expression levels of thousands of genes at once, producing large amounts of data. These datasets are valuable only if they are annotated by sufficiently detailed experiment descriptions. However, in many databases a substantial number of these annotations is in free-text format and not readily accessible to computer-aided analysis. RESULTS: The Multi-Conditional Hybridization Intensity Processing System (M-CHIPS), a data warehousing concept, focuses on providing both structure and algorithms suitable for statistical analysis of a microarray database's entire contents including the experiment annotations. It addresses the rapid growth of the amount of hybridization data, more detailed experimental descriptions, and new kinds of experiments in the future. We have developed a storage concept, a particular instance of which is an organism-specific database. Although these databases may contain different ontologies of experiment annotations, they share the same structure and therefore can be accessed by the very same statistical algorithms. Experiment ontologies have not yet reached their final shape, and standards are reduced to minimal conventions that do not yet warrant extensive description. An ontology-independent structure enables updates of annotation hierarchies during normal database operation without altering the structure. AVAILABILITY AND SUPPLEMENTARY INFORMATION: http://www.dkfz.de/tbi/services/mchips

Algorithms↗