PSMB9 and melanoma: We assessed the mRNA expression levels of standard proteasome subunits (PSMB5 [Swiss-Prot:P28074], PSMB6 [Swiss-Prot:P28074], PSMB7 [Swiss-Prot:Q99436]) and immunoproteasome (IP) subunits (PSMB8 [Swiss-Prot:P28062], PSMB9 [Swiss-Prot:P28065], PSMB10 [Swiss-Prot:P40306]) in our database of 55 melanoma cell lines by gene expression array analysis [21, 22] (Fig. 1).