OBJECTIVE: To study the relationship between oval cells and primary hepatocarcinoma and the expression of c-kit and proliferating cell nuclear antigen (PCNA) in oval cells of rats with hepatocellular carcinoma.
METHODS: A hundred and twenty clean SD rats were divided into three groups: normal group, cancer-induction group and intervention group. The normal group was fed with standard forage while the rest two groups were fed with 3’-methyl-2-methylamino-azobenzene (DAB) to induce carcinoma for 14 weeks and then fed with standard forage and water. Uscharidin was injected abdominally to the intervention group from the first week to the 14th week. All rats were killed and biopsy specimens were taken from the left and right liver lobes for immunohistochemical staining of c-kit and PCNA on the 2nd, 4th, 6th, 8th, 10th, 12th, 14th, 16th, 18th, 20th, 22nd, and 24th week.
RESULTS: From the 2nd to 14th week after liver infection, c-kit positive cells, mainly oval cells were found in the portal area in the carcinoma-induction group and dotted positive pigmentations in liver lobules. In the 22nd week, a large number of cancerous nodes occurred and nuclei heteromorphism was apparent; the number of positive cell decreased but positive cells could be sparsely observed in cancerous nodes. In the 2nd week of the carcinoma-induction process, PCNA positive cells were oval cells in the portal area. In the 4th week, a lot of hepatic cells were positively stained, especially in the central vein area. In the 6th week, PCNA positive cells could be seen in the lobules of the liver. In the 8th week, the number of PCNA cells decreased comparatively. From the 10th to 14th week, oval cells in the portal area were still over-expressed. From the 16th to 24th week, a large number of cancerous nodes occurred and PCNA was over-expressed in some of them. In necrotic cancerous nodes, the para-cancerous PCNA positive cells were sparsely distributed and their number was less than that of PCNA positive cells of cancerous tissues.
CONCLUSIONS: Hepatic stem cells originating from the terminal biliary plexus of the portal area are involved in the development of hepatocarcinoma because c-kit positive cells expressed in cancerous nodes, accompany the whole process of the development. In the middle inflammatory period of carcinoma-induction, the expression of PCNA in hepatic cells peaked, but the index decreased in the late inflammatory period and in the proliferated fibrosis stage. The expression of PCNA is a tortuous process, going up, down, then up again from normal tissues to cancerous tissues. Combined with pathological findings, PCNA can be considered as a warning index for carcinomatous cells.