CDKN1A and hepatocellular carcinoma: To date, many genes involved in HCC occurrence, development, and progression have been comprehensively studied in depth, including p53, p21[2], p16, beta-catenin, PTEN, and Rb. Recent studies of HCC using functional gene screening have further revealed that a number of genes with novel sequences and unclarified functions are related to HCC development or progression [3].