STAMP2 is a metalloreductase [20,21,22] that is highly expressed in the normal prostate and has a key role in PCa proliferation [23]; in addition, it may also regulate inflammatory homeostasis in a context-dependent manner in different tissues, such as adipose tissue, macrophages, inflammatory skin conditions (psoriasis), and in rheumatoid arthritis (RA) [24,25,26,27]. This evidence concerns the gene STEAP4 and rheumatoid arthritis.