Mapping of Tumor Stem Cells in the Resection Marigin During Extirpation of Highly Malignant Gliomas Using GlioStem

Background Glioblastoma (GBM) is the most malignant primary brain tumor with an annual incidence of around 3 in 100 000. The tumors are often found in a late stage of the disease and untreated patients have a median survival of only 3 months. Current state-of-the-art treatment includes maximal surgical resection, followed by concomitant radiochemotherapy. However, despite state-of-the-art treatment the prognosis remains dismal with median survival of less than two years. At recurrence, there is no standard of care, and further treatment including renewed surgery, chemotherapy re-challenge or bevacizumab offers only very limited prolongation of survival.

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. It is convincingly demonstrated that GSCs possess tumor initiating abilities. GSCs also seem to escape conventional therapy due to their slow metabolism, and they can be in quiescent states for long times. GSCs can extend into the healthy tissue from the actual tumor, which is challenging for the surgeon as the healthy cells and the GSCs cannot be distinguished in real-time by 5-aminolevulinic acid (5-ALA) fluorescence guided resection or other proven methods or by other proven methods. Furthermore, as it is known that GSCs are resistant to chemo- and radiotherapy - and targeting of GSCs significantly reduces the risk for lethal relapse - being able to detect and eliminate GSCs during tumor resection would mean a crucial step towards increased patient survival. Hence, there is a need for better methods for precise removal of GSCs with minimum damage to healthy tissue to improve GBM prognosis and quality of life of operated patients.

Other studies in vitro and in animal models have pointed to the importance of GSCs for the recurrence and therapy resistance of gliomas. Targeting these cells specifically or tumor regions specifically dense in such tumor initiating cells - either macroscopically during a surgical procedure or with drugs specifically aimed at these subpopulation of cells - may therefore be an important aim in efficiently preventing tumor regrowth.

Celluminova's core technology is centered around the molecular luminescent biomarker GlioStem, which, unlike 5-ALA, is indicative of GSCs. GlioStem is an oligothiophene derivative sprung from research at KI and Linköping University (LiU), which can penetrate physiological cell membranes and selectively binds to structures inside the GSCs. GlioStem is conveniently administered onto the investigated tissue or cell culture by a pipette. After only a few minutes, the GSCs will emit green light from GlioStem molecules under blue illumination. The high luminescence specificity for the GSCs has been verified in large in vitro studies, including a great variety of human and animal cells, and in animal models. Moreover, we have shown that the high GlioStem specificity permits efficient separation of GSCs from astrocytes and other GBM cells by fluorescence-activated cell sorting (FACS). As GlioStem detects the quiescent slow-dividing GSCs that are not seen with Gliolan or by other methods, it can give valuable complementary information to Gliolan during fluorescent-guided tumor resection. As previously mentioned, it is known that GSCs are resistant to chemo- and radiotherapy. Therefore, being able to detect and eliminate GSCs during tumor resection would mean a crucial step towards increased patient survival.

In previous studies, we have shown that the cancer stem cell marker GlioStem can efficiently and with high specificity identify tumor cells with stem cell genotype in tissue samples from GBM (unpublished data). We now intend to study the extent to which this can be used to guide the procedure in a tumor resection to identify areas in the marginal zone where cancer stem cells can be identified and where extended resection would be particularly beneficial.