Tumor heterogeneity in small hepatocellular carcinoma: analysis of tumor cell proliferation, expression and mutation of p53 AND beta-catenin.

Most hepatocellular carcinomas (HCCs) first occur as well-differentiated HCCs, from which poorly differentiated HCC cells develop because of dedifferentiation. In this study, we try to clarify the changes of dedifferentiation and cell proliferative activity and their relationship in small HCCs (less than 3.0 cm in diameter) and try to learn the mechanism of these changes by analysing the expressions and genetic changes of proliferation-related genes p53 and beta-catenin. Of 41 surgically resected small HCCs, 11 were identified to have tumor heterogeneity. DNA from the 11 small HCCs, consisting of 29 intratumoral lesions and 11 noncancerous liver tissues adjacent to HCCs, was extracted from paraffin embedded tissue sections. Exons 5-8 of p53 gene and exon 3 of beta-catenin gene were amplified by polymerase chain reaction and analyzed by direct sequence. The serial sections were also immunostained by anti-Ki-67, p53 and beta-catenin antibody. Immunohistochemistry showed that the p53 overexpression was significantly related to the proliferative activities as evaluated by Ki-67 immunostaining and to the histological differentiation. The expression of beta-catenin was found to be heterogeneously distributed not only in various histological grades of the same tumor but also in areas of the same histological grade. p53 and beta-catenin gene mutations were detected in 1 tumor respectively, both of which were second primary HCCs and also recurred later. The p53 mutation showed the same mutation pattern in heterogeneous subpopulations. beta-catenin mutation was detected only in the less differentiated lesion but not in the well-differentiated lesion of tumor. In conclusion, our findings suggest that there was histological heterogeneity in small but established HCC, which was accompanied by increased proliferative activity and p53 overexpression. The overexpression of beta-catenin may be related to the proliferative activity and dedifferentiation of HCC.

Expression of vascular endothelial growth factor in surgical specimens of hepatocellular carcinoma.

PURPOSE: Vascular endothelial growth factor (VEGF) has been reported to play an important role in angiogenesis in hepatocellular carcinoma (HCC). However, there is great variation in reports on the distribution of VEGF expression, especially in non-carcinoma liver cells. Furthermore, some reports have mentioned that endothelial cells were positive for VEGF antibody but have not evaluated its significance. In this study, we focused our attention to these problems and try to solve them. We also analyzed the factors influencing VEGF expression and evaluated the prognostic potential of VEGF protein in HCC. METHODS: We examined the VEGF expression in specimens surgically removed from 46 HCC patients and 3 patients with liver cancer metastatic from the colon, and in 4 specimens of liver tissue with benign disease, by immunohistochemical methods. RESULTS/CONCLUSIONS: VEGF was expressed in HCC cells and hepatocytes and on vascular endothelial cells. Our finding that about seven times more endothelial cells were positive for VEGF antibody in carcinoma areas than in non-carcinoma areas (P < 0.001) suggests that VEGF is a very important angiogenesis factor for HCC growth. VEGF expression in HCC cells and non-carcinoma liver cells and on endothelial cells did not closely correlate with the disease recurrence rate (P > 0.05), suggesting that VEGF expression may not be useful as an individual factor for estimating the prognosis of HCC. A statistical analysis of the relationships between VEGF expression and clinicopathological variables revealed the following: preoperative transcatheter arterial embolization enhanced VEGF expression in both HCC cells and non-carcinoma liver cells. The histological grade of HCC and the level of alanine aminotransferase was related to VEGF expression in non-carcinoma liver cells and on endothelial cells in HCC areas. Tumor size and the histological status of the accompanying chronic hepatitis also influenced the VEGF expression on endothelial cells. Our findings concerning not only HCC but also the surrounding liver and endothelial cells may provide useful information for further research on the role of VEGF expression in HCC patients.