S100A9 and neoplasm: In CRC, metastasis and tumor growth has been associated with elevated levels of circulating and tumor localized MDSCs that release cytokine/chemokine/ protein within the tumor microenvironment (CCL2, CCL15, S100A8, and S100A9) and activate signaling pathways such as MAPK and NF-κB for sustained growth [67,68].