CCNA1 and Epstein-Barr virus infection: Another environmental factor, such as EBV infection, was reported to be associated with genetic mutations (AKT2, CCNA1, MAP3K4, and TGFBR1) and hypermethylation (ACSS1, FAM3B, IHH, and TRABD) in GC tissues; AKT2 mutation was associated with a poor survival in GC patients with EBV infection [20].