TABLE 3.

PD-1 expressed on tumor cells.

Cancer type	Tumor cell-intrinsic PD-1 function	Mechanism	References
Melanoma	PD-1 promoted tumor growth	PD-1 increased the level of phosphorylation of S6, mTOR components, and eIF4E	Kleffel et al. (2015), Schatton et al. (2010)
Hepatoma		PD-1 increased the level of phosphorylation of S6, mTOR components, and eIF4E	Li et al. (2017)
Pancreatic cancer		PD-1 activated the hippo pathway and increased the expression of CYR61 and CTGF.	Pu et al. (2019)
NSCLC	PD-1 inhibited tumor growth	Mechanism was not specified	Du et al. (2018)
Lung cancer		PD-1 inhibited the activation of AKT and ERK signaling	Wang et al. (2020c)

mTOR, mammalian target of rapamycin; eIF4E, eukaryotic initiation factor 4E; CYR61, cysteine-rich angiogenic inducer 61; CTGF, connective tissue growth factor; NSCLC, non-small-cell lung carcinoma; ERK, extracellular signal-regulated kinase.