The
plant sterol guggulsterone has been shown to exert anti-
tumor effects, making it a candidate chemotherapeutic agent. We investigated the anti-
tumor effects of
guggulsterone on
colon cancer cells and elucidated the underlying molecular mechanisms related to angiogenesis. The apoptotic effects of
guggulsterone were examined by cell survival assay. Western blot analysis was used to determine the levels of various down-stream intracellular
proteins involved in angiogenesis, including
signal transducer and activator of transcription 3 (STAT3),
vascular endothelial growth factor (
VEGF),
hypoxia-inducible factor-1alpha (HIF-1alpha) and
aryl hydrocarbon receptor nuclear translocator (ARNT). Using
chromatin immunoprecipitation assay, we tested whether
guggulsterone affects the recruitment of STAT3, ARNT and HIF-1alpha to the human
VEGF promoter. To investigate the effect of
guggulsterone on vascular endothelial cell migration and invasion, tube formation and migration assays were conducted using human umbilical vein endothelial cells (HUVECs).
Matrix metalloproteinase (MMP)-2 and -9 activities were measured by
gelatin zymography.
Guggulsterone significantly reduced cell viability in
colon cancer cells in a dose-dependent manner and blocked
VEGF, ARNT and STAT3 expression prominently in hypoxic conditions. The recruitment of STAT3 and ARNT, but not HIF-1alpha, to the
VEGF promoter was inhibited by
guggulsterone treatment. HUVECs produced much foreshortened and severely broken tubes and showed decreased migration activity under
guggulsterone effects. In addition, zymography revealed that MMP-2 and -9
enzyme activities were markedly lower in the presence of
guggulsterone. The results of this study suggest that
guggulsterone not only induces apoptosis, but also inhibits angiogenesis and
metastasis in
colon cancer cells by blocking STAT3 and
VEGF expression, suggesting its therapeutic potential in the treatment of
colorectal cancer.