ULBP2 and cholangiocarcinoma: In addition, the GSE40967 cohort based on the GEO database was used to validate the prognostic values of NKG2DL, the results suggested that the expression of the ULBP2 gene [adjusted P = 0.036, HR (95% CI) = 1.423 (1.024–1.979)] was related to the RFS of CC; meanwhile, the expression of the MICB gene (adjusted P = 0.037, HR (95% CI) = 0.722 (0.532)–0.980)] and ULBP2 gene [adjusted P = 0.005, HR (95% CI) = 1.563 (1.146–2.130)] were related to the OS of CC (Supplementary Figure 5, Supplementary Table 4).