PDCD1 and lung cancer: As far as the molecular function is concerned, NDUFS2 silencing inhibits mitochondrial complex I activity and dramatically decreases tumor growth and metastasis rates in lung cancer (Liu L. et al., 2019), and NDUFS4 knockdown in melanoma cells results in decreased oxidative metabolism, significant decreased CD8+ T cell numbers but with superior functional, and an increased response to anti-PD-1 therapy (Najjar et al., 2019).