CHI3L1 and glioblastoma: Additional biomarkers indentified by the analysis exhibiting greater increases in relative expression levels (> 30 fold) and/or lower p values (< 7.90 × 10-11), include CHI3L1 (Figure 8B), RGS5 (Figure 8C) and IGFBP2 (Figure 8D), which have been shown to be over expressed in malignant astrocytomas - particularly recurrent glioblastomas that often contain a higher percentage of brain tumor stem cells [27,28] - suggesting that these may be more reliable biomarkers of brain tumor stem cells than CD133 (PROM1).