Expressions Of Cell Cycle Regulatory Components In Human Hepatocarcinogenesis

Objective: To study the expressions and correlations of cell cycle regulatory components in the hepatocellular carcinogenesis and to identify the molecular mechanism of hepatocarcinogenesis. Methods: cyclinDl, CDK4, PCNA, p16 andp27 proteins were detected by immunohistochemical staining in total 107 samples of chronic hepatitis, liver cirrhosis, paratumor cirrhosis, hepatocellular carcinoma (HCC), and normal liver tissues. P16 messenger RNA (mRNA), p27mRNA weredetected by in situ hybridization (ISH) in these tissues. Results: No expressions ofcyclinDl, CDK4 and PCNA in normal liver tissues, but the positive unit (PU) and area number density (N_A) of positive cells from chronic hepatitis, liver cirrhosis, paratumor cirrhosis to hepatocellular carcinoma (HCC) were gradually increased and the expressions of these proteins were the highest in HCC. CyclinD1 and CDK4 protein levels were noted to be higher in paratumor cirrhosis and HCC than in chronic hepatitis and liver cirrhosis (P<0.05), whereas there was no significant difference between the expressions in paratumor cirrhosis and in HCC (P>0.05). Theexpressions of p16 protein and mRNA in normal liver tissues and chronic hepatitis were lower, and they were continuously higher form liver cirrhosis, paratumor cirrhosis to HCC. The expressions of p16 protein and mRNA in paratumor cirrhosis were significantly higher than that in liver cirrhosis (P<0.05), but there were no significant differences between the expressions in paratumor cirrhosis and that in HCC (P>0.05). P16 protein level was generally concordant with p16 mRNA level. P27 protein level was increasingly higher from normal liver tissues to paratumor cirrhosis, whereas the expression of p27 protein in HCC was strongly reduced. There were significant differences between the expression of p27 protein in HCC and that in the other grounds (P<0.05). P27 mRNA level in noncarcinoma tissues were significant higher than that in HCC (P<0.05). In addition to, there were cytoplasmic staining patterns of cyclinDl, CDK4, p16 and p27 positive cell in paratumor cirrhosis and HCC, while nuclear staining patterns in chronic hepatitis and liver cirrhosis. The poor differentiation of HCC was, the higher expression of PCNA and the lower expressions of p16, p16mRNA, p27 and p27mRNA (P<0.05). In HCC, PCNA protein level was positively correlated with cyclinD1, CDK4 protein levels. There were significantly negative correlations between p27 protein level andPCNA, cyclinDl and CDK4 protein levels. Conclusions: These results indicatedthat alterations of various components of the cell cycle regulatory machinery should be involved the occurrence and development of HCC, associating the differentiation of HCC. The paratumor cirrhosis may be a sequential lesion of precancerous cirrhosis around HCC. The overexpressions of cyclinDl and CDK4 appear to be important events in early-stage of hepatocarcinogenesis. The high-level expression of p16 may be resulted from positive feedback regulation of cell cycle, which should be a molecular event in early phase of hepatocarcinogenesis, while reduce or loss ofp16 may be a late-stage event. Reduce or loss of p27 protein and p27mRNApotentially involved in hepatocarcinogenesis. Cytoplasmic staining patterns of cyclinDl, CDK4, p16 and p27 positive cell may be associated with the occurrence of HCC. The expression level of PCNA could be used to identify the malignant degree and tumor cell differentiation.