TMOD-08. SERUM ESTABLISHED CANCER STEM CELL CULTURES REPRESENT UNIQUE MODELS OF GLIOBLASTOMA INTER-TUMOR HETEROGENEITY

Abstract Glioblastoma (GBM) is the most frequent primary malignant brain tumor. The invasive and heterogeneous nature of GBM stem cells (GSCs) provide the basis for extreme therapy resistance of GBM and the majority of patients survive less than one year from diagnosis. Relevant models of GBM are important for basic research and drug screening and development, and the current consensus in the field is that GSCs are most faithfully maintained under serum-free neural stem cell (NSC) conditions. We have used serum-free NSC media to explant 230 patient-derived GBM samples, and have in parallel also explanted the same samples in regular serum-containing media. We found, accordingly, that serum-free media was most effective in generating sustainable cultures (137/230, 60%), called serum-free (SF) cultures. Interestingly, we also found that that there was a subgroup of GBM specimens that could only be established in serum-containing media (31/230, 13%), called exclusive serum-containing (eSC) cultures. We characterized a number of the eSC cultures and found that they expressed typical GSC markers such as MSI-1, BMI-1, nestin, CD44 and SOX2. They also displayed all functional characteristics of GSCs, i.e. extended proliferation, sustained self-renewal and orthotopic tumor initiation. Molecular analyses showed that the eSC cultures were most closely related to but separated from mesenchymal subtype GBM. In summary we have established GSC cultures that would have evaded modeling under serum-free conditions, representing unique cell models of GBM inter-tumor heterogeneity. Key words: Glioblastoma, serum cultures, stem-like cells, GBM heterogeneity