Also, neural precursor cells (NPCs) from the subventricular zone (SVZ) produce chemo-attractants (Secreted Protein Acidic And Cysteine Rich [SPARC/SPARCL1], Heat Shock Protein 90B [HSP90B], and pleiotrophin) that facilitate glioma invasion of the SVZ through rhomboid/Rho associated kinase (Rho/ROCK) signaling [98]. Here, PTN is linked to central nervous system cancer.