Zheng et al. illustrated that before BC lung metastasis, lung MSCs are stimulated by Th2 cytokines such as IL-4/IL-13 via the STAT6 pathway to release high levels of complement component 3 (C3), thereby attracting neutrophils to the lungs through the C3-C3aR axis and form the NETs 53. This evidence concerns the gene C3AR1 and breast cancer.