FN1 and glioblastoma: We then performed qPCR for FN and its EDA and EDB splice variants, revealing that samples from SVZ GBM had 22-fold increased expression of EDA (P < 0.001), a marker we found to be highly expressed by CAFs, and 22-fold more FN expression (P < 0.001), but just 5-fold increased EDB expression (P = 0.02) normalized relative to the tumor core (Figure 6B).