p2l is a universal inhibitor of cycle-dependent kinase (cdk) and of cell-cycle progression, the expression of which is regulated by p53 dependent and p53 independent pathway. p21 expression is known to vary in a pattern that depends on the tissue type and type of disease. To study the role of p21 in the hepatocarcinogenesis, the expression of p21, p53 and Ki-67 were investigated in 4 cases of low grade dysplastic nodules, 3 cases of high grade dysplastic nodules, 7 cases of early hepatocellular carcinomas (HCCs), 27 cases of small HCCs (<3cm), 52 cases of advanced HCCs (>3cm) and 53 cases of inactive liver cirrhosis. p21 expression wasn not detected in meitotically inactive lesions of liver cirrhosis, low grade dysplastic nodules, high grade dysplastic nodules and early HCCs. p21 expression was increased significantly in meitotically active lesions of small HCCs
and advanced HCCs. Loss of p21 expression was found in 55.5% of small HCCs and 53.8% of advance HCCs. The p21 expression was significantly correlated with Ki-67 labelling indices. p53 was not expressed in liver cirrhosis, dysplastic nodules and early HCCs, however its expression was significantly higher in small and advanced HCCs. The p21 expression was not correlated with p53 expression. These results suggest that p21 has cell-cycle regulatory function in meitotically active lesions and p2l and p53 play a role in the progression of early HCCs to small HCCs and the p2l expression is regulated by p53 independent pathway in the hepautocarcinogenesis.