CTSK and bone neoplasm: Generally elevated cathepsins' activity was observed in TAM.Cathepsin K modulates the immune response in a SCID-hu mouse bone tumor model by recruiting TAM via CCL2 and promoting expression of cathepsin B and COX2 (42).Several cathepsins can process COX2 in its mature form, thereby influencing immunosupressive PGE2 production (43).Cathepsin S releases CD74 intracellular domain, which in turn activates NF-kB-dependent CCL2 transciption (44).Cathepsins B and S, secreted from TAM, protect tumor cells from paclitaxel, etoposide and doxorubicin induced apoptosis (45).