S100A9 and neoplasm: Other inflammation related factors, such as VEGF-A, TGF-β, and TNF-α, released by the primary tumor, have also been reported to induce the recruitment of BMDCs to the formation site of the pre-metastatic niche and these inflammation chemokines also induced the expression of inflammation proteins (S100A8 and S100A9) that made the parenchyma strongly chemoattractive for BMDCs and tumor cells [105].