Decreased ID2 promotes metastatic potentials of hepatocellular carcinoma by altering secretion of vascular endothelial growth factor.
OBJECTIVE
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).


METHODS
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-1alpha 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-1alpha 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.
Tsunedomi
Ryouichi
R
Department of Digestive Surgery and Surgical Oncology, Yamaguchi University Graduate School of Medicine, Yamaguchi, Japan.
Iizuka
Norio
N
Tamesa
Takao
T
Sakamoto
Kazuhiko
K
Hamaguchi
Takashi
T
Somura
Hideaki
H
Yamada
Mamoru
M
Oka
Masaaki
M
D014408:Biomarkers, Tumor / Q000032:analysis; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D018572:Disease-Free Survival; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D051793:Hypoxia-Inducible Factor 1 / Q000378:metabolism; D051797:Inhibitor of Differentiation Protein 2 / Q000378:metabolism*; D053208:Kaplan-Meier Estimate; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D009361:Neoplasm Invasiveness / Q000503:physiopathology*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D014408:Biomarkers, Tumor; D051793:Hypoxia-Inducible Factor 1; C497450:ID2 protein, human; D051797:Inhibitor of Differentiation Protein 2; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A