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 increasingWHOstageandpoorprognosisofpatients'survival.GSCsrepresenttheleastvulnerable,thusmostpreferentialtarget cellpopulationtobeexposedtovarioustherapeuticmodalities,althoughtheunderlyingmechanismsofthisresistancearenotyet fully understood. For the development of GSC-targeting therapies, further in depth studies are needed using enrichedand stable GSCcellpopulations.Here,wediscussthecurrentapproachesofGSCisolationandvalidationbasedonexpressionofstemness 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.