To further investigate the specific mechanism by which cathepsins are involved in the regulation of the prognosis in GBM, we screened the PPIs of CTSB, CTSL, CTSZ/X (cysteine protease), and CTSD (aspartic protease) according to the public database STRING (https://cn.string-db.org, accessed on 30 December 2021) to figure out the potential downstream targets. The gene discussed is CTSD; the disease is glioblastoma.