CTLA4 and pachyonychia congenita: To validate whether the ICK-related genes were transcriptionally altered in PC, the authors retrieved the expression data of 19 ICK-related genes from The Cancer Genome Atlas Database (n = 494); CD28, CD274, CTLA4, LAG3, PDCD1LG2, TNFRSF14, TNFRSF18, and TNFSF18 gene expression analysis revealed significant differences between tumor and normal tissues (p < 0.05).