Breast cancer-derived CAV1 promotes lung metastasis by regulating integrin α6β4 and the recruitment and polarization of tumor-associated neutrophils.

Lung metastasis in breast cancer (BC) patients is one of the main reasons for their high mortality rate. The most prevalent BC small extracellular vesicles (sEVs receptor, integrin α6β4, has been found to interact with surfactant-associated protein (SFTPC) in lung epithelial cells, making BC more likely to metastasize to the lung. Tumor-associated neutrophils (TANs) play an essential role in BC lung metastasis as a component of the lung pre-metastatic niche (PMN) with two sides. It has been demonstrated that Toll-like Receptor4 (TLR4) can participate in signaling, such as NF-B and NLRP3, to facilitate tumor metastasis. A cellular membrane structural protein called caveolin-1 (CAV1) is associated with BC's proliferation, metastasis, and immunological control. According to our previous research, CAV1 on BC-derived sEVs facilitates the formation of the lung PMN by enhancing tenascin-C (TnC) secretion in lung fibroblasts to promote the deposition of ECM, by increasing the expression of PMN marker genes and inflammatory chemokines in lung epithelial cells, and by supporting N2-type polarization of lung macrophages via inhibiting the PTEN/CCL2/VEGF-A axis. More research is needed to determine how sEVs-mediated CAV1 facilitates BC-targeted metastasis to the lungs. By creating a stable-translocating cell line that stably interfered with CAV1 and a mouse model of BC lung metastasis, we investigated how sEVs-mediated CAV1 promotes BC lung metastasis and TAN recruitment and polarization in vivo and in vitro. In this study, we showed that CAV1 increases the likelihood that BC lung metastasis would occur by controlling the expression of integrin α6β4 and via boosting TANs recruitment and polarization through activating the TLR4-NF-B-IL-6/CCL2 and TLR4/NF-B/NLRP3 signaling pathways. According to our findings, CAV1 regulates integrin α6β4 and modulates TLR4 signaling, both of which are critical for BC lung metastasis. This finding may open new avenues for BC lung metastasis prevention and treatment.