Partial blockage of hepatocyte maturation in hepatoma-derived growth factor transgenic mice

Overexpression of hepatoma-derived growth factor in melanocytes does not lead to oncogenic transformation

BACKGROUND

HDGF is a growth factor which is overexpressed in a wide range of tumors. Importantly, expression levels were identified as a prognostic marker in some types of cancer such as melanoma.

METHODS

To investigate the presumed oncogenic/transforming capacity of HDGF, we generated transgenic mice overexpressing HDGF in melanocytes. These mice were bred with mice heterozygous for a defective copy of the Ink4a tumor suppressor gene and were exposed to UV light to increase the risk for tumor development both genetically and physiochemically. Mice were analyzed by immunohistochemistry and Western blotting. Furthermore, primary melanocytes were isolated from different strains created.

RESULTS

Transgenic animals overexpressed HDGF in hair follicle melanocytes. Interestingly, primary melanocytes isolated from transgenic animals were not able to differentiate in vitro whereas cells isolated from wild type and HDGF-deficient animals were. Although, HDGF-/-/Ink4a+/- mice displayed an increased number of epidermoid cysts after exposure to UV light, no melanomas or premelanocytic alterations could be detected in this mouse model.

CONCLUSIONS

The results therefore provide no evidence that HDGF has a transforming capacity in tumor development. Our results in combination with previous findings point to a possible role in cell differentiation and suggest that HDGF promotes tumor progression after secondary upregulation and may represent another protein fitting into the concept of non-oncogene addiction of tumor tissue.

Significance of HDGF expression in hepatocellular carcinoma tissue and HepG2 cells

AIM: To investigate the expression of hepatoma-derived growth factor (HDGF) in hepatocellular carcinoma (HCC) tissue and HepG2 cells and to analyze its significance.

METHODS: Ten HCC tissue samples and matched noncancerous tissue samples were collected. The mRNA expression of HDGF in these HCC samples, noncancerous tissue samples and HepG2 cells was detected by real-time RT-PCR. The protein expression of HDGF in 137 HCC tissue samples and 49 normal liver tissue samples was examined by immunohistochemistry. The relationship between HDGF expression and clinicopathological parameters in HCC was then analyzed.

RESULTS: The expression levels of HDGF mRNA were 21.11 and 11.39 times higher in HCC tissue and HepG2 cells than in noncancerous tissue, respectively. The positive rate of HDGF expression in HCC tissue was significantly higher than that in normal liver tissue (77.4% vs 51.5%, P = 0.011). High expression of HDGF protein was positively correlated with T classification, N classification and clinical stage (all P < 0.05) in HCC patients. Univariate Cox analysis showed that HDGF expression, N classification and clinical stage had significant correlation with survival prognosis of HCC patients (P = 0.028, 0.041 and 0.000; HR = 1.557, 1.526 and 2.316, respectively). Multivariate analysis showed that HDGF expression might be an independent prognostic indicator (P = 0.000, HR = 0.358) for the development and progression of HCC. Patients with higher HDGF expression showed a significantly shorter overall survival time than those with low HDGF expression.

CONCLUSION: HDGF is highly expressed in HCC tissue and HepG2 cells. High HDGF expression is an independent prognostic factor in HCC patients. High HDGF expression is associated with poor overall survival in patients with HCC.