The role of transcriptional repression in the tumor response to TOP2 inhibitors

• Applicant: Dr. Shiwei Deng
• Subject Area: Pharmacology
• Term: from 2010 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 183726200

Inhibitors of topoisomerase II (TOP2) such as doxorubicin or etoposide are applied to all cancers responsive to chemotherapy, but their molecular effects are incompletely understood. My unpublished data indicate that TOP2 inhibitors repress the transcription of a small and specific set of genes involved in DNA repair and cell cycle. I hypothesize that this suppression results from drug-stabilized complexes of TOP2 and DNA and that it contributes to tumor cell killing by TOP2 inhibitors.To better characterize and confirm gene suppression as a general mechanism of TOP2-induced apoptosis, global gene expression will be investigated in various tumor cell lines treated with clinical TOP2 inhibitors. To confirm that TOP2-dependent gene suppression is indeed caused by transcription inhibition of drug-stabilized TOP2-DNA complexes (as opposed to e.g. reduced RNA stability), the transcription rate of selected TOP2-repressed genes will be measured by “run-on” technique. Chromatin immunoprecipitation assays will be conducted on the same genes to demonstrate complexes between DNA and poisoned TOP2 and their location. To demonstrate that TOP2-mediated transcriptional repression contributes to tumor cell killing by TOP2 inhibitors, the expression and/or activity of selected TOP2-suppressed genes will be manipulated by means of siRNA technology or by chemical inhibitors. This will be accompanied by characterization of relevant phenotypes such as apoptosis, DNA repair, or mitotic abnormalities.These investigations will identify key genes, transcriptional suppression of which induces cell killing upon treatment with TOP2 poisons. These genes may allow for the elucidation of the individual determinants of the response to anthracyclines. They may also be useful as targets for development of more specific and less toxic anthracycline-like drugs.

• DFG Programme: Research Grants