IDH1 and glioma: Our findings indicate that GPR133 is expressed in both IDH wild-type and mutant tumors of grades II–IV, but is not found in non-neoplastic brain tissue, including the subventricular zone that harbors neural progenitors thought to give rise to gliomas.15 In addition, GPR133 is expressed not only within the tumor bulk, but also in the brain-infiltrating tumor edge.