CHRNA4 and glioblastoma: In view of these literature data, we decided to study the expression of nAChR genes via patient-derived GBM microsphere cultures [31] using real-time PCR after culturing cells in two types of medium: without fetal bovine serum (but with bFGF and EGF growth factors and NS-21 neuronal vitality supplementation) and with FBS (Figure 3).