Decreased ID2 Promotes Metastatic Potentials of Hepatocellular Carcinoma by Altering Secretion of Vascular Endothelial Growth Factor

Purpose: We aimed to explore the molecular and biological functions of Inhibitor of DNA binding/differentiation 2 ( ID2 ), which was found to be responsible for portal vein invasion of hepatocellular carcinoma (HCC). Experimental Design: We measured ID2 mRNA levels in 92 HCC patients by real-time reverse transcription-PCR and examined the relation to clinicopathologic features. To clarify the precise roles of ID2 , we did in vitro analysis with expression vectors and small interfering RNAs. Effects of ID2 on cell invasive potential and expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α were analyzed by Matrigel-coated invasion chamber, ELISA, and Western blot analysis, respectively. Results: ID2 mRNA level correlated inversely with portal vein invasion ( P < 0.001), tumor-node-metastasis stage ( P < 0.001), tumor size ( P < 0.001), and early intrahepatic recurrence ( P < 0.05). When limited to a cohort of hepatitis C virus–related HCCs, patients with low levels of ID2 had significantly shorter disease-free survival time than those with high levels of ID2 . Invasive potential of cells transfected with ID2 expression vector was lower than that of empty vector–transfected cells. Cells overexpressing ID2 also showed decreased VEGF secretion and hypoxia-inducible factor-1α protein levels. The results of ID2- knockdown experiments were opposite to those of ID2 overexpression experiments. Conclusions: On the basis of our clinical and in vitro data, we suggest that ID2 plays a significant role in the metastatic process during progression of HCC. This action might be explained, at least in part, by altered cell mobility due to decreased secretion of VEGF.