Glioblastoma stem-like cells: approaches for isolation and characterization

Glioblastoma (GBM) stem-like cells (GSCs) represent the most undifferentiated state of malignant cells with distinct biological characteristics. The fraction of these cells within a glial brain tumor, ranging from 2–30%, is correlating with the increasingWHOstage andpoor prognosis of patients' survival. GSCs represent the least vulnerable, thusmost preferential target cell population tobeexposed to various therapeuticmodalities, although the underlyingmechanismsof this resistance are not yet fully understood. For the development of GSC-targeting therapies, further in depth studies are needed using enriched and stable GSCcell populations. Here, wediscuss the current approaches ofGSC isolation and validation basedon expression of stemness and oncogenic markers as well as on functional assays. The enrichment of GSC phenotypes in established cell lines and/or primary tumor cultures, achieved by different strategies, is reviewed, providing a comprehensive comparison of selected studies and contemplating the characterization of the plethora of variants of reported GBM population exhibiting the GSC phenotype.