This analysis shows these cells are enriched in transcriptomic signatures associated with mesenchymal and embryonic stem cells (Fig. 1a), thought to be the most aggressive cell subsets and critical contributors of therapeutic resistance.16,17 Next, we performed a similar analysis comparing transcripts differentially regulated in GBM patients upon recurrence (i.e. second resection and after receiving therapy) and non-tumor brain tissue and compared this gene list to the transcripts induced by Oct4 and Sox2 in our patient-derived neurospheres. This evidence concerns the gene POU5F1 and neoplasm.