CDKN2A and esophageal squamous cell carcinoma: In addition to investigating HPV infection in EC, our group has also previously assessed the expression of molecular markers p53 and p16, considered to be essential G1 cell cycle regulatory genes whose loss of function is associated with ESCC carcinogenesis [41], and found that the expression of these proteins was significantly higher in tumor tissues compared to adjacent normal tissue to the tumor and also esophageal tissue from individuals without EC [25].