Cyclin D1 overexpression in hepatocellular carcinoma

BACKGROUND/AIMS: Cyclin D1 gene amplification and cyclin D1 protein overexpression have been reported in various human tumors, including hepatocellular carcinoma (HCC). However, their significance is still controversial. In the present study, we examined the expression of cyclin D1 and its relationships to p53 and Ki-67 in HCCs. METHODS: The expression and topological distribution of cyclin D1, p53 and Ki-67 in 50 cases of HCC were examined immunohistochemically, and the relationship between the expression of these proteins and their pathologic features was investigated. RESULTS: Overexpression of cyclin D1 was noted in 58% of the HCC cases, and significantly associated with a well-differentiated histology and a low Ki-67 labeling index (LI). Cyclin D1 overexpression was also observed in all (7 of 7) dysplastic nodules and in non-neoplastic hepatocytes. On the other hand, aberrant p53 expression was detected in 36% of the cases, which showed positive relationships with poor differentiation, portal vein invasion, and KI-67 LI. Only eight of the 50 cases examined (16%) were positive for both cyclin D1 and p53, which showed only a small number of cyclin D1-positive cells. There was no significant relationship between the expressions of cyclin D1 and p53. CONCLUSIONS: Our results suggest that cyclin D1 overexpression may be an early event in hepatocarcinogenesis and that it plays a role in tumor differentiation. In addition, cyclin D1 expression is not correlated with tumor cell proliferation in HCCs.