PDCD1 and head and neck squamous cell carcinoma: By analyzing the expression of lncRNA AC131097.3 and PD-1 in HNSCC tissues and normal adjacent tissues from TCGA and in isolated leukocytes, it was noticed that lncRNA AC131097.3 and PD-1 are coexpressed, and that both of them are inversely correlated with promoter methylation and positively correlated with CpG methylation [102].