PSMB9 and neoplasm: Tumor cells demonstrated enriched expression of the proteasome and immunoproteasome subunits Psmb8 and Psmb9 and major histocompatibility complex class I (MHC I) genes H2-K1, H2-D1, and B2m, consistent with upregulation of antigen processing and presentation machinery (Fig. 6e, Supplementary Figure 16d).