Kinase activity profiling in pediatric brain tumors: a novel strategy for the identification of drugable targets

PhD ceremony: Mr. A.H. Sikkema, 11.00 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Kinase activity profiling in pediatric brain tumors: a novel strategy for the identification of drugable targets

Promotor(s): prof. E.S.J.M. de Bont, prof. M. Peppelenbosch, prof. W.A. Kamps

Faculty: Medical Sciences

This thesis describes the optimization of the kinase activity profiling protocol and data processing, to generate comprehensive insight in pediatric brain tumor kinase activity and cell signaling network. Based on the obtained kinase activity profiles, a number of potential targets for therapeutic drug options were selected. Subsequent in vitro studies provided valuable insights in their roles in pediatric brain tumor progression. Here, active Src signaling was found to be essential to pediatric brain tumor survival. Selectively vascular expression and activity of VEGFR2 was observed in pilocytic astrocytoma. Aberrant EphR expression and activity proved to be of critical importance in mediating medulloblastoma invasion. In vivo validation of these new insights in aberrant pediatric brain tumor signal transduction should be pursued to establish the therapeutic application of these targets. The kinetic readout of peptide substrate phosphorylation provided new insights in the basic factors determining the selectivity of kinase-substrate interactions within the cell. Here, a high diversity in the relevance of the primary amino-acid sequence in determining substrate specificity urges more study of the fundamental factors driving selectivity and sensitivity of protein-protein interactions in order to establish effective and specific kinase targeting. Altogether, array-based kinase activity profiling provided invaluable and comprehensive insight in the pediatric brain tumor signal transduction network. Although substantial challenges in optimizing peptide substrate annotation and data interpretation remain, further implementation of kinase activity-based tumor characterization studies should become a focal point in the optimization of mechanism-based anticancer therapeutic strategies.