PDCD1 and neoplasm: Moreover, PD-L2 not only possesses higher affinity for PD-1 than PD-L1 does but also may be highly coexpressed with PD-L1 in tumor cells and tissues (Youngnak et al., 2003; Cheng et al., 2013; Morales-Betanzos et al., 2017; Tang and Kim, 2019; Furuse et al., 2020; Wolkow et al., 2020).