SHH and central nervous system cancer: In our study, mGluR4, a typical G-protein-coupled receptor whose activation is negatively coupled to adenylate cyclase and reduction in intracellular cAMP level, was shown to decrease the Gli-1 level in LN229 cells, indicating that activation of mGluR4 might control the excessive expression of Gli-1, consequently inhibiting the growth of glioma cells through inactivation of the SHH pathway.