A 3D in vitro glioblastoma cell culture system for identification and evaluation of novel radiosensitisers reducing rodent xenograft studies

Glioblastoma (GBM) is the most common primary brain tumor. Tumors exhibit inherent chemo- and radioresistance which has been attributed to a subpopulation of cancer cells termed 'GBM stem-like cells' (GSC), and almost inevitably recur. While preclinical studies have shown promising activity of several molecularly targeted agents against GBM cell lines, these agents have failed to improve clinical outcomes for patients. The failure of drug-radiation combinations with promising preclinical data to translate into effective clinical treatments may relate to the frequent use of established GBM cell lines in simplified two-dimensional (2D) in vitro cultures.

We have developed a novel 3D-Alvetex GBM model system that recapitulates key histological features of GBM including high cellularity, sparse extracellular matrix and presence of GSC. Using this model, we have reproduced clinical outcomes including (i) lack of response to EGFR-directed therapies alone and in combination with radiation and (ii) enhancement of radiosensitivity by VEGF targeting, providing evidence for this culture model as a clinically relevant platform for evaluating targeted therapies alone and in combination with radiation. Genomic characterisation (RNASeq) of two different primary GBM cell lines grown in this 3D system, has identified 71 transcripts that are upregulated following radiation treatment. Following validation of transcripts for which inhibitors are commercially available, using RT-PCR in the 3D model and IHC in an existing human GBM TMA and in house human orthotopic glioblastoma xenografts, we will evaluate the radiosensitising properties of target inhibitors in the 3D model and in a novel multicellular 'perivascular niche' system comprising 3D GSC and human brain endothelial cells. We believe that our models will provide meaningful preclinical assessment of novel molecular targets, improving accuracy of in vitro drug evaluation while reducing and partially replacing in vivo models.