Gene and Protein Expression in Human Gliomas

Abstract: The human gliomas are the most common primary brain tumours. They are highly aggressive with a rapid fatal progression for the patient. The invasive growth pattern and inherent resistance to radiation and chemotherapy account for a lack of efficient therapies. Several novel therapeutic regimes are being investigated, but they have so far shown limited beneficial effects. The molecular heterogeneity of the gliomas has also made it difficult to define the tumourigenic pathways, and to efficiently subcategorise the tumours according to different molecular origin or therapeutic sensitivity. The aims of this thesis has been to gain novel insights in the genetic and proteomic events underlying tumourigenesis and malignant progression in gliomas, and potentially define specific key events that could be the object of refined or novel therapeutic approaches. We have utilised gene expression microarrays and 2D differential in-gel electrophoresis (DIGE) with sequential tandem mass spectrometry (MS/MS) protein identification, to investigate the gene and protein expression profiles in a set of gliomas of varying grades, as well as in a number of normal human brain samples. We found that these platforms can efficiently discriminate samples according to their histopathological origin. Both platforms also identified central tumourigenic pathways, deregulated in gliomas. The gene expression analysis further identified several chromosomal regions with deregulated expression. We also identified a number of proteins overexpressed in gliomas as potential objects for targeted therapy. From the combined data we conclude that there is a very weak correlation between mRNA and protein expression. Furthermore, we investigated the tissue distribution patter and cellular location of the potential tumour associated antigen Ku70/80. We show that the extracellular localisation of this protein complex is specific for tumour cells, and that it can be used as a portal for tumour specific delivery of toxin conjugated antibodies. Finally, using antibody microarrays we investigated differences in immunoregulatory proteins detected in the plasma of glioblastoma tumour patients and normal controls, as well as in tumour patients undergoing immunotherapy against gliomas. We found that patients can be stratified according to the beneficial effect of the immunotherapy. We also identified a number of key immunoregulatory factors discriminating the different subgroups. These data provide novel insight into tumour immunologic processes, and a step towards refinement of the immunotherapeutic regimes.