Inflammatory chemoattractant proteins S100A8 and S100A9, induced by various TDSFs like VEGF-A, TNF-α, and TGF-β, facilitate the infiltration of Mac1+ myeloid cells into the lung PMN.65 Moreover, VEGF emanating from the primary tumor modifies the lung microenvironment in the pre-metastatic phase by inciting an inflammatory response and producing PGE2, a pivotal element in the establishment of the PMN.40 Prior research has demonstrated that TDSFs can attract MDSCs to the PMN. Here, S100A9 is linked to neoplasm.