Insulin-like growth factor binding protein-1 over-expression in transgenic mice inhibits hepatic preneoplasia

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Abstract
Insulin‐like growth factor binding protein‐1 (IGFBP‐1) is synthesized in the liver and regulates the mitogenic effects of the insulin‐like growth factors (IGFs). The evidence that IGFBP‐1 plays a role in hepatocarcinogenesis, however, is equivocal. We have, therefore, investigated the development of preneoplastic hepatic lesions in transgenic mice in which the human IGFBP‐1 gene is under the control of the mouse metallothionein promoter. The lesions were induced by treating 15‐d‐old male mice with a single intraperitoneal injection of 5 mg/kg diethylnitrosamine (DENA). Lesions were scored when the mice were 28 wk of age. Quantitative microscopy of liver sections revealed that significantly fewer transgenic mice treated with zinc to activate the transgene had focal lesions compared to either transgenic mice not treated with zinc or wild‐type mice treated with zinc (36.4% versus 85.7% and 83.3%, respectively, P < 0.05 in each case). Zinc‐treated transgenic mice also had significantly fewer lesions per liver (11.5 ± 5.0 versus 74.7 ± 18.4 and 59.4 ± 15.6, respectively, P < 0.01 in each case) and a smaller percentage of liver volume occupied by lesions (0.2 ± 0.1 versus 1.4 ± 0.3 and 1.1 ± 0.4 respectively, P < 0.05 in each case). Immunohistochemical staining showed that both IGF‐I and IGF‐II were overexpressed in most of the lesions. These results show that expression of the IGFBP‐1 transgene leads to a marked inhibition of hepatic preneoplasia, possibly by decreasing the mitogenic activity of IGF‐I and/or IGF‐II. This study adds new evidence to the notion that the IGF axis plays an important role in liver cancer development.

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