Core Viewpoint - The study reveals that tumor-antigen-specific cytotoxic CD8+ T cells can be deployed remotely to inhibit lung metastasis of breast cancer, highlighting the importance of effector immune cell deployment in cancer treatment [3][8][11]. Group 1: Research Findings - The abundance of tumor-specific CD103+ CD8+ T cells in tumor-draining lymph nodes (TDLN) is associated with prolonged disease-free survival in breast cancer patients [8]. - CD103+ CD8+ T cells are activated in TDLN and recruited to the lungs via CCL25/CCR9 signaling, effectively suppressing tumor metastasis [8][9]. - Tumor-derived extracellular vesicles (EVs) polarize alveolar macrophages, leading to the release of CCL25 and IDO1, which can inhibit the deployment of CD103+ CD8+ T cells and promote lung metastasis [8][9]. Group 2: Implications for Cancer Treatment - Enhancing the recruitment of CD103+ CD8+ T cells or blocking IDO1 can potentially curb lung metastasis of tumors [9]. - The study emphasizes the adaptive immune system's capability to deploy remotely to protect distant organs from tumor metastasis, suggesting a potential therapeutic strategy in cancer treatment [11].