POSTN and glioblastoma: Interestingly, POSTN, a known ECM protein involved in the crosstalk between GBM and microglia [38], displays and even higher upregulation in the GBM – astrocyte co-culture and the triculture with 3.56- and 3.41-fold, respectively, compared to the GBM/microglia co-culture with 1.63-fold, indicating that astrocytes might even play a more important role in the expression of POSTN.