Research Report 2010 - MDC

Structure of the GroupUlrike ZieboldGroup LeaderDr. Ulrike ZieboldGraduate StudentsChristna ChapKirsten VormbrockBjörn von EyßSebastian MemczakKatharina MöllmannTechnical AssistantsGitta BlendingerCynthia VossSecretariatPetra HainkSonja GieringGenetics of Tumor Progression andMetastasisThe mammal cell cycle has been extensively studied nevertheless its intricacies remainelusive. Furthermore, the knowledge of cancer stem cells is at its beginnings. To tackle thesecomplex questions, we modify murine ES-cells to characterize both transcriptional and signalingmodules in stemness, proliferation or differentiation. Similarly, we use mouse models to definethe molecular circuitry underlying cancer causing stem cells. Central to our work is theunderstanding of the molecular consequences of deregulation of the retinoblastoma protein(RB) and E2Fs, since in most human tumors the RB pathway is mutated leading to unfetteredactivity of the E2F transcription factors. To reveal how E2Fs control growth, we search forinteraction partners and chromatin modifiers. We are also interested in the specific contributionof E2F3 to tumor progression by identifying novel metastasis specific targets. In summary, ourgoal is to understand how specific biological processes as cellular stemness, growth control andsuppression of tumorigenesis are coupled.Interaction partners and possible co-activatorsof E2F3Björn von Eyss and Katharina MöllmannThe inactivation of the RB tumor suppressor pathwaydepends on the activity of the E2F-transcription factors,since in pRB mutant mice E2F3 contributes extensivelyto the ectopic S-phase and apoptosis. Depleting E2F3alone leads to cellular growth defects but the molecularmechanism of E2F3 is not understood. Searching forspecific interaction partners of E2F3, we identified anumber of novel molecules, among them putative chromatinregulators. For some of these regulators we wereable to show that they can be detected on E2F-regulatedpromoters, that they are essential for the progressionthrough cell cycle and are co-expressed with E2F3in human tumors. Lastly, we are using ChIP coupled todeep sequencing to reveal the whole scope of co-regulatedtarget genes. So far, our genome wide searchrevealed unanticipated E2F-target genes, which will befocus of our future research.E2F target genes in proliferation and metastasisKirsten Vormbrock and Sebastian MemczakE2f3 is the only E2F amplified in human tumors, wherebyhigh E2F3 expression marks invasiveness predictingpoor patient survival. This led to the hypothesis thatE2F3 regulates unique sets of target genes. To search forsuch targets we use a mouse strain deficient for bothpRB/E2F3. In this model, merely few pRB-deficient micedevelop small medullary thyroid carcinomas (MTCs),while most pRB/E2F3 deficient mutants developmetastatic MTCs. Using micro-array gene-chips weestablished the transcriptional profile of these MTCs.The resulting sets of transcripts are putative metastaticmarkers. Importantly, for four of these markers anidentical pattern in human metastatic thyroid malignancieswas found, a first proof that these genes areprognostic markers. Judged by chromatin immune precipitationassays, all of the genes are direct targets ofE2F. Thus, we link individual E2F-action to specific E2Ftargetgenes and the onset of metastasis.88 Cancer Research