Recent studies have revealed that
1,2,3,4,6-penta-O-galloyl-beta-d-glucose (
PGG) has anti-tumorigenic activity in vitro. In the present work, we evaluated the in vitro and in vivo antiangiogenic and antitumor activities of
PGG and examined its molecular mechanisms.
PGG significantly inhibited the proliferation and tube formation in
basic fibroblast growth factor (bFGF)-treated human umbilical vein endothelial cells (HUVECs) at non-cytotoxic concentrations.
PGG effectively disrupted the bFGF-induced neo-vascularization in chick chorioallantoic membrane (CAM) and in
Matrigel plugs in the mice. When mice were intraperitoneally injected,
PGG also significantly inhibited
tumor angiogenesis induced by
Lewis lung carcinoma (LLC) and the growth of LLC by 57 and 91% of control
tumor weight at 4 and 20 mg/kg, respectively. Immunohistochemical analysis revealed decreased microvessel density, decreased expression of
cyclooxygenase-2 (COX-2) and
vascular endothelial growth factor (
VEGF), reduced
tumor cell proliferation and increased
tumor cell apoptosis. Similarly,
PGG significantly attenuated the expression of COX-2 and
VEGF and reduced the secretion of
VEGF and
prostaglandin E2 in bFGF-treated HUVECs. Furthermore, the
COX-2 inhibitor NS398 significantly inhibited tube formation and neo-vascularization in CAM, supporting the role of COX-2 in
PGG inhibition of angiogenesis.
PGG diminished the phosphorylation of
extracellular signal regulated kinase 1/2, Jun NH2-terminal
kinase and activated phospho-p38
mitogen-activated protein kinase (MAPK) in a dose-dependent manner in bFGF-treated HUVECs. In addition, p38 inhibitor
SB203580 abolished the downregulation of COX-2,
VEGF and the antiproliferative activity by
PGG. Taken together, our data demonstrate that
PGG exerts antitumor activity primarily via inhibition of angiogenesis through COX-2 and MAPK- dependent pathways.