Single nucleotide polymorphisms (SNP) in genes, such as ALDH7A1 [81], POLA2 [82], LIG1 [83], and ERCC6L [84], are important for the development of various cancers, such as esophageal squamous cell carcinoma, lung cancer, and oral cancer, but these polymorphic genes may be linked with pathogenesis of BRCA. The gene discussed is POLA2; the disease is lung cancer.