Because CTH was the only metabolic gene emerging from our CRISPR screen whose pharmacologic targeting inhibited invasion in spheroid invasion assays (Figure 5C) and because cystathionine, a precursor to cysteine in glutathione synthesis in the transsulfuration pathway, was enriched in the invasive fraction of both patient-derived tumor biopsies and 3D hydrogels (Figure 1C), we focused further investigation on the specific role of CTH in GBM invasion. The gene discussed is CTH; the disease is glioblastoma.