POSTN and glioma: Periostin, a downstream target of PDGFB signaling in pericytes, is known as a proangiogenic extracellular matrix component in glioma [211], and plays an important role in regulating cell migration and epithelial–mesenchymal transition through binding with integrins to activate cell focal adhesion kinases; it is also involved in angiogenesis, the polarization of M2 TAMs, and tumor progression [201,212,213].