Study On Morphologic Features And Expressions Of Cell Cycle Regulatory Components During DEN-Induced Hepatocarcinogenesis In Rat

Objective: In order to explore the molecular mechanism of hepatocarcinogenesis, the morphologic features and expressions of cell cycle regulatory components in the stage of precancerous lesions and early hepatocarcinoma during DEN-induced rat hepatocarcinogenesis were studied. The emphasis of this study lay on comparative study of the stage of precancerous lesions and early hepatocarcinoma, and the relationship of these lesions.Methods: DEN was used to establish rat liver cirrhosis-cancer model; The expression of cyclinDl, CDK4, P27~kip1and P51tip2 protein in total 85 samples of normal liver tissues, hyperplasia nodule, paratumor hyperplasia nodule, liver cirrhosis, paratumor cirrhosis, borderline nodule, paratumor borderline nodule and hepatocellular carcinoma were detected by immunohistochemistry methods. Results: 87.17%(34/39) hepatocarcinoma were induced by DEN. The procession of hepatocarcinogenesis in this model included three stages-hepatic toxic lesion, hepatic proliferation/cirrhosis and hepatic carcinogenesis. This experimental hepatocarcinoma rat model induced by DEN is similar with the human hepatocellular carcinoma not only in forming procession but also in morphologic features.Therewere no significant differences between the stage of precancerous lesions and theparatumor corresponding lesions both in morphologic features and the expression ofcyclinDl, CDK4, P27kip1and P57kip2 protein (P>0.05) . In the hepatocarcinogenesisinduced by DEN, there were significant differences between the normal liver tissuesand others in the expression of cyclinD 1 and CDK4 protein (P<0.05) .There were nosignificant differences among all groups in the expression of P27klp1 protein (P>0.05).There were significant differences between the normal liver tissues and hyperplasianodule and liver cirrhosis in the expression of P57kip1 protein (P<0.05 ) , the same wasin groups of borderline nodule , hyperplasia nodule and liver cirrhosis(P<0.05 ) .According to immunohistochemistry staining, this 4 kinds of protein wereexpressed in nuclear in normal liver tissues except for cyclinDl , but in experimentalgroups, they were expressed in cytoplasm or nuclear . There were significantdifferences between the normal liver tissues and other experimental groups in nuclear/cytoplasm staining of cyclinDl and P57kip2 protein (P<0.05) . There were significantdifferences between the hepatocellular carcinoma and other groups in nuclear/cytoplasm staining of CDK4(P<0.05 ). There were significant differences between thehepatocellular carcinoma and normal liver tissues and hyperplasia nodule in nuclear/cytoplasm staining of P27kip2 protein (P<0.05 )T Conclusions: This liver cancer modelinduced by low dose DEN is a more useful experimental model for the study ofhepatocarcinogenesis. The paratumor hyperplasia nodule, paratumor cirrhosis andparatumor borderline nodule around HCC should be sequential lesions ofprecancerous corresponding lesions during hepatocarcinogenesis. The results of theexpression of cell cycle regulatory components indicated that alterations of theexpression of cyclinDl, CDK4 and P57kip2 were involved the occurrence anddevelopment of HCC. The overexpression of cyclinDl and CDK4 appear to beimportant events in early-stage of DEN-induced hepatocarcinogenesis. The abnormalexpression of P57kip2 was involved the occurrence of HCC. P27kip1 protein maybedon't play the restrained role in hepatocarcinogenesis. Cytoplasmic staining patternsof cyclinDl, CDK4, P27kip1 and P57kip2 protein may be associated with the occurrenceof HCC.