Novel, biologically relevant, in vitro model of the blood-brain tumour barrier (BBTB)

Glioblastoma (GBM) is the most common form of brain cancer. Despite this, treatment has not improved significantly in the past 20 years. Current therapy involves surgery, radiotherapy and chemotherapy, but outcomes remain very poor, with average life expectancy for newly diagnosed patients ranging from 12 to 14 months. The lack of progress in treatment options is multifaceted, but targeted therapy options have yet to overcome the challenge of crossing the blood-brain barrier (BBB) / blood-brain tumour barrier (BBTB). Current models of the BBTB fail to provide an accurate representation of the disease. In vitro 2D cell cultures do not reflect the complexity of the BBTB, and have limited relevance to human physiology. In vivo models may not mimic the clinical disease; novel drugs that work on GBM xenograft models have not been successful in the clinic.

The objective of this project is to establish and biologically validate a novel in vitro model of the BBTB by inclusion of GBM cells with the current BBB model. This will be achieved using a hydrogel transwell, consisting of human derived GBM cells, co cultured with brain like endothelial cells derived from induced pluripotent stem cells (iPSCs). The working hypothesis of this project is that this method will generate a biologically relevant model of GBM at the BBB which can then be validated, and used as a screen for novel, targeted therapies. The NC3Rs have funded this project as this model could be used to replace some rodent xenograft studies.

Our collaborators at the Open University have recently established a novel BBB model based on deriving brain-like endothelial cells from iPSCs and co-culturing with astrocytes on a hydrogel. This model has been fully validated and forms a tight monolayer with expression of key BBB proteins. The monolayer of BECs on top of the hydrogel transwell culture provides an ideal model where the barrier properties and function can be investigated directly. To achieve the inclusion of GBM cells within the BBB model, our collaborator at University of Edinburgh has provided neural stem cells (NSCs) and patient derived GBM stem-like cells (GSCs). These GBM cells, alongside astrocytes, will be cultured in the hydrogel component of the model. This technique enables the establishment of an in vitro BBTB and a way to study the effects of the GBM cells.

The validity of this model will be determined using several criteria: barrier tightness; astrocyte end feet; gene expression; drug crossing and tight junction protein expression will be assessed. Finally, using transcriptomics, the novel in vitro BBTB model will be compared to GBM patient datasets of the BBTB to define the biological relevance of the in vitro model to the human disease.
The impact of this model will be to reduce animal usage significantly and in the longer-term have the potential model to replace GBM xenograft models. We estimate an approximate use of at least 4,500 rodents a year for GBM xenograft experiments in the UK. For the worldwide usage of GBM xenograft rodents, a search shows nearly 800 primary publications published in the last year that used GBM xenograft models. From this we estimate at least 60,000 rodents are used per year worldwide for GBM xenograft studies. The use of an in vitro model as a primary screen for novel drug therapies would lead to an estimated 20% reduction in animal work, and therefore approximately 12,000 rodents a year that would not be used in GBM research. In conclusion, this project aims to generate a validated BBTB model that can be rolled out to GBM labs, thus leading to the reduction in the use of GBM xenograft models and improved translation to the human disease.