ALDH18A1 and glioblastoma: This is supported by the expression of canonical proline pathway associated genes pyrroline-5-carboxylate reductase 1 (PYCR1) and ALDH18A1 (encoding P5CS protein) being expressed at higher levels in published GBM transcriptomic datasets (n = 418) relative to normal brain (n = 216) (Fig. 6B–C).