SPP1 and neoplasm: Analysis of these differentially expressed cytokines indicated that pro-metastatic osteopontin (OPN) [44] and SLPI [45,46,47,48] in both TEMs (in vitro) and TAMs (in vivo) are most strongly induced by tumor CCL5. Our previous work had established OPN and SLPI as markers of macrophages activated by CCL5 [11], and both of these factors have been shown to directly regulate tumor cell invasiveness [44,45,46,47,48].