Our data suggest that higher grade gliomas do not co-express BTK and SOX2 extensively and we speculate that the GSC models we use ex vivo, which are typically SOX2+/BTK− as shown in Fig 6 are most likely representative of the dominant cancer cell type in the tumour tissue which are SOX2+/BTK− (48%, Fig 10F). This evidence concerns the gene SOX2 and neoplasm.