Of the two PDGF tyrosine kinase receptors (PDGF-α and PDGF-β), PDGF-α is expressed in an autocrine manner in glioma cells, whereas PDGF-β is expressed in glioma endothelium and pericytes, particularly the latter, suggesting its importance in the migration of pericytes into newly formed blood vessels [39]. This evidence concerns the gene NTRK1 and central nervous system cancer.