In addition, activation of mGluR3 inhibits bone-morphogenetic protein receptor induced differentiation by activating the MAPK pathway, and that treatment with an mGluR3 receptor antagonist suppresses in vivo tumor growth in a mouse intracranial glioblastoma model of implanted CD133+ stem cells (or tumor-initiating cells as we refer to them) [10]. The gene discussed is GRM3; the disease is glioblastoma.