STEM-14. NEAR-INSTANT DETECTION OF GLIOMA STEM CELLS IN LIVE HUMAN GBM-TISSUE

Emerging research suggests that failure to target glioma stem cells (GSCs) rather than the inability to remove tumors through surgery, radiation, or chemotherapy, explains the poor survival of GBM patients. In this study, a luminescent conjugated oligothiophene (LCO), named GlioStem (p-HTMI), is used for non-invasive and non-amplified real-time detection of GSCs in live human GBM-tissue. More than 90 patient samples were stained, quantified, and analyzed by fluorescent microscopy for the presence of Gliostem-positive (GS+) cells. Approximately 30 of the samples were FACS-sorted for GS+ and GS- cells where quantification by FACS could verify microscopy results. In addition, GS+ cells were shown to express significantly higher levels of stem cell markers (CD271, CD133, PDGFRa, CD44) in FACS-experiments. Bulk RNA sequencing of 7 GBM patient samples with paired GS+ and GS- sorted cells revealed that GS+ patient samples clustered together, whereas the GS- populations did not cluster together neither with each other nor with the GS+ populations. These data suggest a distinct heterogeneity in the GS- samples and a certain level of homogeneity regarding the GS+ populations, independent of intra-patient or patient-to-patient heterogeneity. Moreover, the GS+ samples were found to express significantly higher levels of stem cell markers including SOX10, OLIG1/2, and ASCL1, compared to the GS- samples. More specifically, the GS+ samples exhibited significantly higher expression of 35 genes associated with stemness compared to the GS- samples, with most markers being associated with pre-oligodendrocyte precursor cells (pre-OPCs) and pro-neural subtypes. Our results suggest that GlioStem is a versatile tool for near-instant and selective detection of GSCs in live tumor tissue. Detecting and eliminating these cells during tumor resection may therefore be an important aim in efficiently preventing tumor regrowth and would mean a crucial step towards increased patient survival.