Proteomic analysis underlines the usefulness of both primary adherent and stem-like cell lines for studying proteins involved in human glioblastoma.

Unlabelled: Primary cell lines derived as neurospheres, enriched in cancer stem cells, are currently the focus of interest in glioblastoma to test new drugs, because of their tumor initiating abilities and resistance to conventional therapies. However, not all glioblastoma samples are propagatable under neurosphere culture and not all neurosphere cell lines are tumorigenic. These cells therefore cannot recapitulate the heterogeneity of glioblastoma samples. We have conducted a proteomic analysis of primary glioblastoma cell lines derived either as adherent cells in the presence of serum (n=11) or as neurospheres (n=12). A total of 963 proteins were identified by nano-LC/Q-TOF MS: 342 proteins were found only in neurosphere lines and were mostly implicated in various metabolic and cellular processes, while 112 proteins were found only in adherent cells and mostly linked to cell adhesion. A protein signature of 10 proteins, 9 of them involved in a cell adhesion pathway, characterized adherent lines. Neurospheres were characterized by 73 proteins mostly linked to DNA metabolic processes associated to cell cycle and protein metabolism. In the Repository of Molecular Brain Neoplasia Data, expression of genes coding for several proteins related to adherent cells or neurospheres were of prognostic relevance for glioblastoma.

Biological Significance: Primary cell lines enriched in cancer stem cells (CSC) have become popular models for testing new drugs for glioblastoma. In this proteomic study on an important number of cell lines obtained either as adherent cells in the presence of serum (a classic way to derive cell lines) or as neurospheres (enriched in CSC), we show that each type of cell line displays different GBM-specific features, highlighting that these two culture types are complementary tools for drug screening.