The article "Immune Cell Promotion of Metastasis" by Kitamura, Qian, and Pollard reviews the role of immune cells in the metastatic cascade of cancer. The authors highlight how immune suppressive cells, such as myeloid-derived suppressor cells (MDSCs), regulatory T (Treg) cells, and macrophages, contribute to the protection of metastatic cancer cells from the immune system. These cells can suppress cytotoxic activities of killer cells, recruit other suppressive cells, and promote tumor cell invasion, intravasation, and survival in the circulation. The review also discusses the recruitment of immune cells to pre-metastatic niches, which are established by primary tumors to enhance metastasis. Additionally, it explores the mechanisms by which tumor cells egress from primary sites, survive at metastatic sites, and establish persistent metastatic growth. The authors suggest that targeting pro-metastatic immune cells, particularly macrophages, may be an effective therapeutic strategy. They emphasize the need for a better understanding of the mechanisms underlying immune cell recruitment and activation to design more precise and effective treatments for metastatic diseases.The article "Immune Cell Promotion of Metastasis" by Kitamura, Qian, and Pollard reviews the role of immune cells in the metastatic cascade of cancer. The authors highlight how immune suppressive cells, such as myeloid-derived suppressor cells (MDSCs), regulatory T (Treg) cells, and macrophages, contribute to the protection of metastatic cancer cells from the immune system. These cells can suppress cytotoxic activities of killer cells, recruit other suppressive cells, and promote tumor cell invasion, intravasation, and survival in the circulation. The review also discusses the recruitment of immune cells to pre-metastatic niches, which are established by primary tumors to enhance metastasis. Additionally, it explores the mechanisms by which tumor cells egress from primary sites, survive at metastatic sites, and establish persistent metastatic growth. The authors suggest that targeting pro-metastatic immune cells, particularly macrophages, may be an effective therapeutic strategy. They emphasize the need for a better understanding of the mechanisms underlying immune cell recruitment and activation to design more precise and effective treatments for metastatic diseases.