PSMB9 and cancer: To study the expression patterns of the constitutive proteasome (CP) and immunoproteasome (IP), we first compared the average expression scores of genes encoding the catalytic subunits of CP (PSMB5, PSMB6 and PSMB7) and IP (PSMB8, PSMB9 and PSMB10) in 9491 TCGA tumour samples, across 33 cancer types (see Section 2, Table S1).