CDKN2A and hepatocellular carcinoma: Genes involved in HCC pathogenesis have been classified into four major groups: i) genes regulating DNA damage response (e.g., p53); ii) genes involved in cell cycle control (e.g., RB1, p16INK4A, and cyclin D); iii) genes involved in growth inhibition and apoptosis (e.g., M6P/IGF2R, SMAD2, and SMAD4); and iv) genes responsible for cell-cell interaction and signal transduction (e.g., APC, ß-catenin, and E-cadherin) [35].