GGT5 and glioblastoma: The concomitant upregulation of glutathione turnover enzymes glutathione peroxidase 8 (GPX8) (log2FC = 0.8, P = 0.0002) and GGT5 (log2FC = 8.1, P = 6.7 × 10-7) in invasive GBM cells was suggestive of increased flux through the transsulfuration pathway.