ERAP1 and neoplasm: In addition a set of 15 proteins that participate in the antitumor immune response such as the tumor suppressors PSMB9, ERAP1 and TAP1 or the interferon-stimulated genes IFIT1 and MX1 were found down-regulated in CUL4A-overexpresing cells and up-regulated in CUL4A-silencing models (Figure 7A).