On the other hand, we compared PD-L1 expression levels between the low α9-nAChR (melanoma tissue microarrays, n = 87; TCGA-SKCM cohort, n = 167; melanoma cell line datasets, n = 156) and high α9-nAChR (melanoma tissue microarrays, n = 89; TCGA-SKCM cohort, n = 305; melanoma cell line datasets, n = 20) expression groups and found that PD-L1 expression levels were significantly higher in the samples with high α9-nAChR expression than in the samples with low α9-nAChR expression (** p < 0.01, *** p < 0.001) (Figure 2J, Figures S3D and S4D). Here, CD274 is linked to melanoma.