PDCD1 and lung cancer: The lung cancer cell-derived exosomes can also induce M2 macrophage polarization (Pritchard et al., 2020), and regulate CD45+EpCAM+ cells apoptosis in lung cancer (Lu et al., 2022), and carry circUSP7, which can regulate the miR-934/SHP2 axis in small cell lung cancer (NSCLC) to induce CD8+ T cell dysfunction and anti-PD-1 resistance (Chen et al., 2021).