Interestingly, PD-L2 gene (PDCD1LG2) single nucleotide polymorphisms (SNPs) are associated with lung adenocarcinoma risk in female never-smokers, and 3 of these SNPs were negatively associated with PD-L2 expression in non-tumor tissue, but not in tumor tissue (57). The gene discussed is PDCD1LG2; the disease is neoplasm.