PDCD1 and neoplasm: Beyond that, researchers have explored the mechanisms of resistance of matters such as insufficient tumor immunogenicity, irreversible T cell exhaustion, disfunction of MHC, immunosuppressive microenvironment, and some oncogenic signaling pathways to improve anti-PD1/PDL1 efficacy (Chocarro de Erauso et al., 2020; Lei et al., 2020; Sun et al., 2020).