One recent study revealed that breast cancer-derived exosomal microRNA-200b-3p uptaken by alveolar epithelial type II cells (AEC II) induce the high expression of C-C motif chemokine ligand 2 (CCL2), S100A8/9, MMP9, and colony-stimulating factor 1 (CSF-1) in lung to recruit the myeloid-derived suppressor cells (MDSCs) and promote inflammatory PMN formation (Gu et al., 2021). Here, CSF1 is linked to breast cancer.