Dauricine inhibits insulin-like growth factor-I-induced hypoxia inducible factor 1α protein accumulation and vascular endothelial growth factor expression in human breast cancer cells

Aim: To investigate the effects of dauricine (Dau) on insulin-like growth factor-I (IGF-I)-induced hypoxia inducible factor 1 alpha (HIF-1 alpha) and vascular endothelial growth factor (VEGF) expression in human breast cancer cells (MCF-7). Methods: Serum-starved MCF-7 cells were pretreated for 1 h with different concentrations of Dau, followed by incubation with IGF-I for 6 h. HIF-1 alpha and VEGF protein expression levels were analyzed by Western blotting and ELISA, respectively. HIF-1 alpha and VEGF mRNA levels were determined by real-time PCR. In vitro angiogenesis was observed via the human umbilical vein endothelial cell (HUVEC) tube formation assay. An in vitro invasion assay on HUVECs was performed. Results: Dau significantly inhibited IGF-I-induced HIF-1 alpha protein expression but had no effect on HIF-1 alpha mRNA expression. However, Dau remarkably suppressed VEGF expression at both protein and mRNA levels in response to IGF-I. Mechanistically, Dau suppressed IGF-I-induced HIF-1 alpha and VEGF protein expression mainly by blocking the activation of PI-3K/AKT/mTOR signaling pathway. In addition, Dau reduced IGF-I-induced HIF-1 alpha protein accumulation by inhibiting its synthesis as well as by promoting its degradation. Functionally, Dau inhibited angiogenesis in vitro. Moreover, Dau had a direct effect on IGF-I-induced invasion of HUVECs. Conclusion: Dau inhibits human breast cancer angiogenesis by suppressing HIF-1 alpha protein accumulation and VEGF expression, which may provide a novel potential mechanism for the anticancer activities of Dau in human breast cancer.