Dr. rer.nat. Ulrich Lehmann, Prof. Dr. med. Hans Kreipe
Institute of Pathology
Development and progression of malignant tumours in humans We focus on the analysis of molecular alterations in morphologically defined human tumour biopsies. Primarily, we are analysing small and precancerous lesions, because advanced tumours harbor a huge number of molecular alterations without functional significance and not causally linked to the development and progression of this specific tumour.
More specifically, we analyse the role of altered DNA methylation patterns in the development and progression of malignant tumours in order to understand the clonal evolution in more detail and also to identify potential new molecular markers for the diagnosis and monitoring of tumours in patients.
Acute myeloid leukemias (AML) are caused by malignant transformation of primitive hematopoietic precursor cells in the bone marrow, which leads to a loss of the capacity to differentiate. These neoplasias are characterized by chromosomal abnormalities, specific mutations and alterations in DNA-methylation patterns, which lead to the inactivation of key regulatory genes.
The potential AML precursor lesions myelodysplastic syndrom (MDS) and chronic myeloproliferative disease (CMPD) retain a certain degree of differentiation capacity despite the neoplastic and clonal proliferation. The risk of progression to an acute leukemia is very different in these different MDS and CMPD subclasses. We try to figure out whether and to which extent the alterations in DNA methylation patterns found in acute myeloid leukemia are already found in the precursor lesions. For this purpose we use a new quantitative assay for the detection of DNA methylation employing real-time PCR technology. This methodology can also be applied for the analysis of archival, i.e. formalin-fixed and paraffin-embedded biopsies. The qualitative and quantitative changes in the methylation patterns are correlated with the subtype of the disease, the clinical course and the progression risk. Also the functional consequences of the altered DNA methylation on the level of the gene expression are analysed in the patient biopsies using real-time quantitative PCR.
In addition to contributions to the understanding of the biological basis of MDS and CMPD this project may lead to the identification of new molecular markers, facilitating the diagnosis of the different subtypes and determining the risk of progression to overt leukemia. Besides this project focussing on AML and the precursor lesions we are also analysing the role of altered DNA methylation in epithelial neoplasia (e.g. breast carcinoma).
Dr. rer. nat. Ulrich Lehmann
Laser-assisted microdissection of histological tissue sections; real-time PCR for quantification of DNA and/or RNA; qualitative and quantitative detection of DNA-methylation (genomic sequencing, methylation specific PCR [MSP], quantitative MSP, restriction analysis); all standard methods in molecular biology for the analysis of DNA and RNA (cloning, sequencing, PCR, Southern-, Northern-Blotting etc.); cell culture
Lehmann U, Glöckner S, Kleeberger W, Feist H, von Wasielewski R, Kreipe H. Detection of gene amplification in archival breast cancer specimens by laser-assisted microdissection and quantitative real-time PCR. Am J Pathol 2000;156:1855-1864;
Lehmann U, Hasemeier B, Lilischkis R, Kreipe H. Quantitative analysis of promotor hypermethylation in laser-microdissected archival specimens. Lab Invest 2001;81(4):635-638