Critical role of histone demethylase RBP2 in human gastric cancer angiogenesis.
BACKGROUND
The molecular mechanisms responsible for angiogenesis and abnormal expression of angiogenic factors in gastric cancer, including vascular endothelial growth factor (VEGF), remain unclear. The histone demethylase retinoblastoma binding protein 2 (RBP2) is involved in gastric tumorgenesis by inhibiting the expression of cyclin-dependent kinase inhibitors (CDKIs).


METHODS
The expression of RBP2, VEGF, CD31, CD34 and Ki67 was assessed in 30 human gastric cancer samples and normal control samples. We used quantitative RT-PCR, western blot analysis, ELISA, tube-formation assay and colony-formation assay to characterize the change in VEGF expression and associated biological activities induced by RBP2 silencing or overexpression. Luciferase assay and ChIP were used to explore the direct regulation of RBP2 on the promoter activity of VEGF. Nude mice and RBP2-targeted mutant mice were used to detect the role of RBP2 in VEGF expression and angiogenesis in vivo.


RESULTS
RBP2 and VEGF were both overexpressed in human gastric cancer tissue, with greater microvessel density (MVD) and cell proliferation as compared with normal tissue. In gastric epithelial cell lines, RBP2 overexpression significantly promoted the expression of VEGF and the growth and angiogenesis of the cells, while RBP2 knockdown had the reverse effect. RBP2 directly bound to the promoter of VEGF to regulate its expression by histone H3K4 demethylation. The subcutis of nude mice transfected with BGC-823 cells with RBP2 knockdown showed reduced VEGF expression and MVD, with reduced carcinogenesis and cell proliferation. In addition, the gastric epithelia of RBP2 mutant mice with increased H3K4 trimethylation showed reduced VEGF expression and MVD.


CONCLUSIONS
The promotion of gastric tumorigenesis by RBP2 was significantly associated with transactivation of VEGF expression and elevated angiogenesis. Overexpression of RBP2 and activation of VEGF might play important roles in human gastric cancer development and progression.
Lupeng
L
Li
Lixiang
L
Wang
Ping
P
Song
Xue
X
Geng
Xiuming
X
Liang
Minran
M
Zhou
Yangyang
Y
Wang
Chunyan
C
Chen
Jihui
J
Jia
Department of Biochemistry and Molecular Biology, Shandong University School of Medicine, Jinan 250012, P, R, China. zengjp@sdu.edu.cn.
Jiping
J
Zeng
D000328:Adult; D000368:Aged; D000818:Animals; D018952:Antigens, CD34 / Q000096:biosynthesis; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D019394:Ki-67 Antigen / Q000096:biosynthesis; D008297:Male; D051379:Mice; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000235:genetics* / Q000473:pathology; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000096:biosynthesis; D054840:Retinol-Binding Proteins, Cellular / Q000235:genetics* / Q000378:metabolism; D013274:Stomach Neoplasms; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis* / Q000235:genetics; D023041:Xenograft Model Antitumor Assays
D018952:Antigens, CD34; D019394:Ki-67 Antigen; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C518459:RBP2 protein, human; D054840:Retinol-Binding Proteins, Cellular; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A