SMO and glioblastoma: It has been reported that Shh levels are much higher in the microenvironment of GBMs than in other tissues and that the activation of SHH signaling pathway requires the binding of Shh to the Patched (PTCH) mediated Smoothened (SMO) (PTCH-SMO) receptor complex (21), consequently resulting in a more activated SHH pathway in GBM.