Table 4.

The characteristics of included studies about the NK cells inhibitory receptors and their ligands.

	Marker	Author	Year	Country	Sample size	Measurement	Treatment	Source	Tumor stage	VS	Number of VS	Divide	Outcome	P-value	Follow-up times
Inhibitory receptors of the NK cells	NKG2A	Sun et al. (24)	2017	China	177	Immune histochemistry	resection	Intratumor	NA	High/Low	68/109	cutoff value	OS;DFS	HR (95%CI) 2.13 (1.28,3.56) P=0.0037; HR (95%CI) 1.93 (1.28,2.93) P=0.0018	median OS:1299.7 ± 1974.2 day; median DFS:980.0 ± 1796.1 day
	CD96	Sun et al. (49)	2019	China	236	Flow cytometry	resection	Intratumor	NA	High/Low	NA	cutoff value	OS;DFS	Log-rank test P=0.5027; Log-rank test P=0.0484	NA
	CD158b	Li et al. (43)	2021	China	13	Flow cytometry	SBRT	Peripheral blood	NA	High/Low	5/8	cutoff value	OS;PFS	Log-rank test P=0.273; Log-rank test P=0.003	NA
	TIGIT TIM-3	Yu et al. (50)	2021	China	133	Flow cytometry	palliative/minimally invasive/resection	Peripheral blood	NA	High/Low	65/68	cutoff value	PFS	HR (95%CI) 2.05 (1.24,3.04) P=0.005	NA
Ligands of the NK cells inhibitory receptors	HLA-E	Sun et al. (49)	2017	China	177	Immune histochemistry	resection	Intratumor	NA	High/Low	79/98	cutoff value	OS;DFS	HR (95%CI) 2.68 (1.58,4.56) P=0.0003; HR (95%CI) 2.41 (1.60,3.64) P<0.0001	median OS:1299.7 ± 1974.2 day; median DFS:980.0 ± 1796.1 day

NK, Natural killer; CI, Confidence interval; HR, Hazard ratio; SBRT: Stereotactic body radiation therapy; OS, Overall survival; DFS, Disease-free survival; PFS, Progression-free survival; NA, Not available.