S100A9 and neoplasm: This occurs through the detection of tumor-derived exosomal RNA by TLR3, thereby stimulating the secretion of CXCL5 and CXCL12.59 Prominent representatives of bioactive molecules include myeloid-related proteins such as S100A8 and S100A9, which are abundantly expressed at metastatic sites and serve as potent chemoattractants for neutrophils.60 However, the exact mechanism driving MRPs-mediated neutrophil mobilization remains elusive to date and more in-depth explorations are warranted.