Recently, it has been demonstrated that PD-1 is also expressed on other cells (e.g., Tregs, TAMs, and tumor cells) and that PD-1 therapy enhances antitumor immunity in a diverse cell-dependent manner (Karyampudi et al., 2016; Xiao et al., 2016; Gordon et al., 2017; Yao et al., 2018; Moral et al., 2020; Strauss et al., 2020; Zhang and Liu, 2020; Lim et al., 2021; Zha et al., 2021). The gene discussed is PDCD1; the disease is neoplasm.