At the in vitro experimental level, GCH1 overexpression in glioblastoma cells reportedly increased cell proliferation in vitro and decreased survival in an intracranial glioblastoma mouse model, and GCH1 knockdown was associated with decreased CD44 expression, resulting in the suppression of glioblastoma cell proliferation and decreased self-renewal (28). This evidence concerns the gene GCH1 and glioblastoma.