PDCD1 and neoplasm: The phagocytotic activity of TAMs can be inhibited by factors such as NF-κB-regulated expression of immune checkpoint molecules like PD-1, and TAMs have also been reported to resemble M2 macrophages with a decreased ability to lyse tumor cells and a capability of directly promoting tumor angiogenesis, tumor growth, and metastasis [136,138,139,140,141].