Potential of Carcinogenesis from Hepatic Progenitor Cells in Hepatocellular Carcinoma

BACKGROUND: Whether hepatocellular carcinomas (HCC) arise from dedifferentiation of mature hepatocytes or maturation arrest of hepatic stem cells is controversial. OBJECTIVE: To investigate the malignant potential of hepatic progenitor cells derived from the fetal liver in a mouse model of chemical hepatocarcinogenesis. DESIGN, TIME AND SETTING: The randomized controlled animal experiment was performed at the Animal Experimental Center of Sun Yat-sen University from January to December 2006. MATERIALS: A total of 70 female BALB/c mice aged 6-8 weeks and weighing 20-25 g were used. These mice were randomly assigned to a normal control group (n=10), a model group (n=30) and an experimental group (n=30). Hepatic progenitor cells were obtained from embryonic day (ED) 14 mice. METHODS: Partial hepatectomy was undertaken using the standard method for a two-thirds resection. Thirty mice in the model group were continuously administered 100 μg/L diethylnitrosamine in the drinking water for 12 weeks. Thirty mice in the experimental group received hepatic progenitor cells and diethylnitrosamine, 1×10^6 cells in each mouse. Ten mice in the normal control group were given hepatic progenitor cells and non-supplemented drinking water. Animals were sacrificed at six months to prepare liver samples. Hepatoma nodules were used to make serial sections for determination. MAIN OUTCOME MEASURES: Immunohistochemistry or immunofluorescence was performed for sex-determining region for Y chromosome (SRY), alpha-fetoprotein, placental form of glutathione-S-transferase (GST-P) or cytokeratin 19 in serial sections of the liver and tumor nodules to analyze cell source and characteristics of HCC. RESULTS: Six months later, seven mice developed hepatocellular carcinoma (HCC) and one mouse developed cholangiocellular carcinoma (CCC) in experiment group. Six affected HCC and one affected CCC. There were no significant differences in carcinoma occurrence rate and tumor pathological types between both groups (P＞0.05). About 17.1% of HCCs stained positively for SRY and none of CCCs was positive for SRY in the experimental group. Most of the SRY-positive HCCs expressed GST-P and alpha-fetoprotein, but did not expressed cytokeratin 19. All of CCCs expressed cytokeratin 19 in the cytoplasm, but did not expressed GST-P and alpha-fetoprotein. CONCLUSION: Hepatic progenitor cells have malignant potential in the diethylnitrosamine model of hepatocarcinogenesis, and maintain the immature characteristics of embryonic hepatic stem cells, and still express glutathione-S-transferase and alpha-fetoprotein.