Caveolin-1 Knockdown Decreases SMMC7721 Human Hepatocellular Carcinoma Cell Invasiveness by Inhibiting Vascular Endothelial Growth Factor-Induced Angiogenesis

Abstract EN

Background.

Recently, several studies have demonstrated that caveolin-1 overexpression is involved in apoptosis resistance, angiogenesis, and invasiveness in hepatocellular carcinoma (HCC).

However, the mechanisms underlying caveolin-1-mediated tumor progression remain unclear.

Methodogy.

Lentiviral vectors were used to construct caveolin-1 small interfering RNA- (siRNA-) expressing cells.

Secreted VEGF levels in SMMC7721 cells were evaluated by enzyme-linked immunosorbent assay (ELISA).

SMMC7721 cell proliferation, cycle, apoptosis, and invasiveness were detected by MTT, flow cytometry, Annexin V-FITC/PI, and invasion assay, respectively.

Phospho-eNOS levels in human umbilical vein endothelial cells (HUVECs) cocultured with SMMC7721 cell supernatants were analyzed by Western blot.

Capillary-like tubule formation assay was performed to analyze endothelial tubular structure formation in HUVECs treated with supernatants from caveolin-1 siRNA-expressing SMMC7721 cells.

SMMC7721 implantation and growth in nude mice were observed.

Angiogenesis in vivo was analyzed by immunohistochemical angiogenesis assay.

Results.

Caveolin-1 siRNA-expressing SMMC7721 cells secreted reduced levels of VEGF.

Caveolin-1 RNAi also caused an inhibition of SMMC7721 cell proliferation and cell cycle progression that was accompanied by increased apoptosis.

Supernatants from caveolin-1 siRNA-expressing SMMC7721 cells inhibited cell cycle progression and decreased phospho-eNOS levels in HUVECs.

Endothelial tubular structure formation in HUVECs treated with supernatants from caveolin-1 siRNA-expressing SMMC7721 cells was considerably reduced.

Caveolin-1 siRNA-expressing SMMC7721 cells also showed reduced tumorigenicity and angiogenesis induction in vivo.

Conclusion.

Our results reveal a novel mechanism, whereby caveolin-1 positively regulates human HCC cell invasiveness by coordinating VEGF-induced angiogenesis.