Aim: To investigate the serum level and expression of insulin growth factor II (IGF-II) in liver tissues of rats with early experimental hepatocellular carcinomas (HCC) and its significance in early diagnosis.
Methods: Early experimental hepatocellular carcinomas were induced by diethylnitrosamine (DENA) in 180 male SD rats. Another 20 male SD rats served as control. The IGF-II serum level was measured by ELISA. Immunohistochemistry and electron microscopic immunohistochemistry were used to observe the expression of IGF-II in normal and tumor liver tissues and its ultrastructural location in malignant hepatocytes. The expressions of IGF-II in human hepatoma cell lines HepG2, SMMC7721 and human embryonic liver cell line L-02 were measured by immunocytochemistry. IGF-II mRNA level was studied by in situ hybridization.
Results: IGF-II was expressed in the cytoplasm of both sinusoidal cells in paracancerous cirrhotic liver tissue and malignant hepatocytes in early experimental HCC tissues. Gold particles were seen on the rough endoplasmic reticulum and the mitochondrion in malignant hepatocytes. IGF-II was expressed in the human hepatoma cell lines. The mRNA level of IGF-II was higher in rat liver tumor tissue than in normal rat liver tissue. The serum IGF-II level of the early experimental HCC group was 34.67+/-10.53 ng.ml(-1) and that of the control group was 11.75+/-5.84 ng.ml(-1). The rank sum test was used for statistical analysis. There was a significant difference between the two groups (P<0.01).
Conclusion: During the induction of early experimental HCC by DENA, IGF-II may promote hepatocytic proliferation via a paracrine mechanism in the pre-cancerous stage. When hepatocytes are transformed into malignant cells, they may secrete IGF-II and promote malignant cell proliferation by an autocrine mechanism. IGF-II may be a possible biological marker in the early diagnosis of HCC.