BACKGROUND:Human chorionic gonadotropin (hCG) can play a crucial role in angiogenesis. In the present study, we focused on hCG to gain insight into its potential effects on vasculogenic mimicry (VM) in ovarian cancer cells.METHODS:Ovarian cancer OVCAR-3 cells were incubated with different concentrations of recombinant hCG in 3-dimensional cultures. VM was identified by morphological observations and vascular endothelial cell marker detection in OVCAR-3 cells. Expression of hCG, hypoxia-inducible factor-1α (HIF-1α), and the endothelial cell markers CD31, VEGF, and factor VIII were detected by reverse transcription polymerase chain reaction and western blotting. The effect of hCG on endothelial cell-marker expression in ovarian cancer cells was further explored using small interfering RNA (siRNA) and plasmid-based approaches.RESULTS:Incubation of OVCAR-3 cells with recombinant hCG induced vessel-like network formation, which was accompanied by significant elevation of vascular marker expression. Attenuation of hCG expression by siRNA in OVCAR-3 cells suppressed the expression of endothelial cell markers and HIF-1α by tumour cells. Overexpression of hCG in OVCAR-3 cells resulted in increased expression of endothelial cell markers and HIF-1α.CONCLUSIONS:HCG was crucial for changing the phenotype of OVCAR-3 cells to endothelial-like cells. The effect of hCG induction on VM in ovarian cancer cells is potentially associated with HIF-1α.

OBJECTIVES:Vasculogenic mimicry (VM) is induced by hypoxia in 3-dimensional culture of ovarian cancer cells. By using this 3D model system, we explored the expression of human chorionic gonadotropin (hCG) and its effects on VM formation in ovarian cancer cell line OVCAR-3 both under normoxic and hypoxic conditions. METHODS:Vasculogenic mimicry was identified by morphological observation and detection of vascular cell marker expressed by OVCAR-3. Potential formation of tumor channels was observed by light microscopy and scanning electron microscopy. Expression of vascular cell marker CD31, vascular endothelial growth factor, and Factor VIII were detected by flow cytometry, immunochemistry, and Western blot. Expression of hCG was investigated by enzyme-linked immunosorbent assay, chemiluminescence immunoassay, real-time polymerase chain reaction (PCR), and Western blot. Expression of hypoxia-inducible factor-1α (HIF-1α) was detected by real-time PCR, Western blot, and blocked by small interference RNA. Incubation of OVCAR-3 with recombinant hCG was used to evaluate its effect on VM formation. The specificity of the effect of hCG was assessed by inhibition with the neutralizing anti-hCG antibody. RESULTS:OVCAR-3 cells formed vessel-like network structures and expressed vascular marker significantly under hypoxia in 3D. The expression level of hCG under hypoxia was significantly higher than that under normoxia. Attenuating hypoxia-inducible factor (HIF)-1α expression via small interference RNA resulted in a significantly decreased hCG expression in OVCAR-3, which indicated that the effect of hypoxia on hCG expression was mediated through HIF-1α. Treatment of OVCAR-3 with 5000 mU/mL hCG resulted in the presence of tumor cell-lined vasculature and significant elevation in vascular marker expression, even under normoxia. Expression level of vascular marker and HIF-1α in OVCAR-3 increased in response to hCG treatment in a dose-dependent manner. The effect of hCG was inhibited by the neutralizing anti-hCG antibody. CONCLUSIONS:Human chorionic gonadotropin has the potential to induce VM in OVCAR-3. Human chorionic gonadotropin might have synergistic hypoxia-induced effect on vascular marker and HIF-1α expression.