Response gene to complement 32, a novel hypoxia-regulated angiogenic inhibitor.
BACKGROUND
Response gene to complement 32 (RGC-32) is induced by activation of complement and regulates cell proliferation. To determine the mechanism of RGC-32 in angiogenesis, we examined the role of RGC-32 in hypoxia-related endothelial cell function.


RESULTS
Hypoxia/ischemia is able to stimulate both angiogenesis and apoptosis. Hypoxia-inducible factor-1/vascular endothelial growth factor is a key transcriptional regulatory pathway for angiogenesis during hypoxia. We demonstrated that the increased RGC-32 expression by hypoxia was via hypoxia-inducible factor-1/vascular endothelial growth factor induction in cultured endothelial cells. However, overexpression of RGC-32 reduced the proliferation and migration and destabilized vascular structure formation in vitro and inhibited angiogenesis in Matrigel assays in vivo. Silencing RGC-32 had an opposing, stimulatory effect. RGC-32 also stimulated apoptosis as shown by the increased apoptotic cells and caspase-3 cleavage. Mechanistic studies revealed that the effect of RGC-32 on the antiangiogenic response was via attenuating fibroblast growth factor 2 expression and further inhibiting expression of cyclin E without affecting vascular endothelial growth factor and fibroblast growth factor 2 signaling in endothelial cells. In the mouse hind-limb ischemia model, RGC-32 inhibited capillary density with a significant attenuation in blood flow. Additionally, treatment with RGC-32 in the xenograft tumor model resulted in reduced growth of blood vessels that is consistent with reduced colon tumor size.


CONCLUSIONS
We provide the first direct evidence for RGC-32 as a hypoxia-inducible gene and antiangiogenic factor in endothelial cells. These data suggest that RGC-32 plays an important homeostatic role in that it contributes to differentiating the pathways for vascular endothelial growth factor and fibroblast growth factor 2 in angiogenesis and provides a new target for ischemic disorder and tumor therapies.
An
Xiaojin
X
Institute of Molecular Medicine, Peking University, Beijing, China.
Jin
Yi
Y
Guo
Hongnian
H
Foo
Shi-Yin
SY
Cully
Brittany L
BL
Wu
Jiaping
J
Zeng
Huiyan
H
Rosenzweig
Anthony
A
Li
Jian
J
D020533:Angiogenesis Inhibitors / Q000235:genetics / Q000502:physiology*; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D019927:Cyclin E / Q000502:physiology; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000166:cytology / Q000473:pathology; D016222:Fibroblast Growth Factor 2 / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D008819:Mice, Nude; D009124:Muscle Proteins / Q000235:genetics / Q000502:physiology*; D009389:Neovascularization, Pathologic / Q000503:physiopathology*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000502:physiology; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology; D023041:Xenograft Model Antitumor Assays
D020533:Angiogenesis Inhibitors; D029742:Caenorhabditis elegans Proteins; D018797:Cell Cycle Proteins; D019927:Cyclin E; C541178:HIF-1 protein, C elegans; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; C115049:RGCC protein, human; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2