SPP1 and neoplasm: To determine how the presence of EO cells in the bone alters the tumor microenvironment, we stained the tibia sections for markers corresponding to the four groups tested in Fig. 2: osteopontin and alkaline phosphatase as bone turnover markers, IL-6 and MCP-1 as inflammatory cytokines, alpha-SMA and VEGF as neovascularization markers, and type I collagen and MMP3 as extracellular matrix proteins.