Glial cells encompass multiple types of mature cells with diverse functions (astrocytes, microglial cells, oligodendrocytes) you can think of them as sort of "helper cells" for neurons. In some types of cancers, cells can enter what is considered a "poorly differentiated" state, where they lose some characteristics of a mature cell and become more stem-like. Some of the cell lines our lab generated were from GBM (glialblastoma multiforme) samples.