CD74 and glioblastoma: Seventy five protease inhibitor genes were differentially expressed, of which 3 genes were highly overexpressed, the genes coding for stefin B (CSTB), peptidase inhibitor 3 (PI3 also named elafin) and CD74. Seven out of 8 genes (except CSTB) were validated using RT-qPCR in GBM cell lines.