Primary Glioma Spheroids: Advantage of Serum-Free Medium

In the field of cancer research, in vitro models are widely used to investigate tumor biology as well as new experimental treatments. There is a need to improve these models, making them more in vivo-like, in order to meet the new challenges arising together with emerging knowledge such as the discovery of cancer stem-like cells. When investigating glioblastomas in vitro – and especially the supposed cancer stem cells – three dimensional spheroid models recently came into focus. Spheroids have earlier been derived from commercial glioblastoma cell lines, but in the 1990s the spheroid model was further improved by the introduction of organotypic primary spheroids derived from small tumor fragments preserving tumor tissue characteristics including cell-to-cell interactions, extracellular matrix, macrophages and blood vessels. Most recently – in the cancer stem cell context – spheroids have been derived from single cells from dissociated primary glioblastoma tissue and cultured in serum-free conditions similar to neuronal stem cells. Using this methodology a much better preservation of cancer stem cell features was obtained compared to the use of serum-containing medium. Furthermore, in a study recently performed in our lab we demonstrated similar advantages of culturing primary organotypic spheroids in serum-free medium favoring an in-vivo-like cancer cell phenotype with better preservation of cancer stem cell features. In addition to this, more vascular structures were seen under serum-free conditions suggesting that the close relationship between blood vessels and cancer stem-like cells was better preserved in this medium. As it will be reviewed below, culturing primary spheroids in a serum-free medium adds a new level to the spheroid model suggesting that this model should be included in studies of tumor biology and drug development when possible.