GCH1 and central nervous system cancer: CircLRFN5 can mediate paired related homeobox 2 (PRRX2) via the ubiquitin proteasome pathway, and in gliomas, PRRX2 activates transcriptional upregulation of GTP cyclohydrolase 1 (GCH1) expression, a substance that inhibits ferroptosis by producing the antioxidant tetrahydrobiopterin (BH4).