CTSK and glioblastoma: Here, we report the most robust set of upregulated protease and protease inhibitor genes, which were jointly expressed in GBM tumor tissue and in at least one GBM cell line, i.e. the protease genes TFRC, GFPT2, ERAP2, GPR56 and CTSK, and the protease inhibitor genes CSTB, CD74 and PI3. The proteins, coded by those genes as listed by KEGG and GO identifiers, are involved in antigen processing and presentation (ERAP2 and CD74), lysosomal peptidase activity and its regulation (CTSK, PI3 and CSTB), glutamine metabolism (GFPT2) and phagosome formation (TFRC).