CDH13 and glioblastoma: SNPs in four genes appear for three or more chemicals: GRIP1 (glutamate receptor interacting protein 1), which directs localization of transmembrane proteins; FMN2, a component of p21-based cell cycle arrest; DNER, a transmembrane protein associated with glioblastoma propagation; and the cell membrane cadherin CDH13, an epithelial tumor suppressor.