Modelling glioblastoma tumour-host cell interactions using adult brain organotypic slice co-culture.

Glioblastoma multiforme (GBM) is an aggressive incurable brain cancer. The cells that fuel the growth of tumours resemble neural stem cells found in the developing and adult mammalian forebrain. These are referred to as glioma stem cells (GSCs). Similar to neural stem cells, GSCs exhibit a variety of phenotypic states: dormant, quiescent, proliferative and differentiating. How environmental cues within the brain influence these distinct states is not well understood. Laboratory models of GBM can be generated using either genetically engineered mouse models, or via intracranial transplantation of cultured tumour initiating cells (mouse or human). Unfortunately, these approaches are expensive, time-consuming, low-throughput and illsuited for monitoring live cell behaviours. Here, we explored whole adult brain coronal organotypic slices as an alternative model. Mouse adult brain slices remain viable in a serum-free basal medium for several weeks. GSCs can be easily microinjected into specific anatomical sites ex vivo, and we demonstrate distinct responses of engrafted GSCs to diverse microenvironments in the brain tissue. Within the subependymal zone-one of the adult neural stem cell niches-injected tumour cells could effectively engraft and respond to endothelial niche signals. Tumour-transplanted slices were treated with the antimitotic drug temozolomide as proof of principle of the utility inmodelling responses to existing treatments. Engraftment of mouse or human GSCs onto whole brain coronal organotypic brain slices therefore provides a simplified, yet flexible, experimental model. This will help to increase the precision and throughput of modelling GSC-host brain interactions and complements ongoing in vivo studies.