Gliomas are tumours of the brain, and despite decades of intense research, still maintain a dismal prognosis. Glioblastoma multiforme represents the most malignant (WHO grade IV) incarnation of this tumour, with a median patient survival of ~16 months, and novel therapeutic approaches are required to improve patient outcomes. The cancer stem cell (CSC) pool within the tumour that resist treatment, causes recurrence and ultimately mortality shares properties with normal stem cells, including high resistance to chemoradiotherapy and a low mitotic index. By isolating these resistant quiescent cells and analysing their expression profiles it is hoped that novel therapeutic targets will be revealed that may improve patient outcomes.
In this study the fluorescent dye Oregon Green was used to label glioma cell lines in a 7-day pulse-chase assay. Oregon Green ubiquitously labels cells, and with each the cell division the fluorescent signal is divided 50:50 between each daughter cell. After 7 days the brightest (and thus the least proliferative) fraction of cells can be identified using flow cytometry or fluorescence imaging.
It was found that cells that retain the highest concentration of Oregon Green are more resistant to chemotherapy (temozolomide), radiotherapy, and combination chemoradiotherapy. The quiescent cells are also more migratory than their proliferative counterparts.
We have shown that quiescent cells are innately resistant to the current GBM standard treatments and are more migratory than rapidly dividing cells. We have provided a platform for quickly and easily isolating this quiescent fraction of cells for further analysis.