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

Abstract

To investigate the effects of dauricine (Dau) on insulin-like growth factor-I (IGF-I)-induced hypoxia inducible factor 1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) expression in human breast cancer cells (MCF-7). 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-1alpha and VEGF protein expression levels were analyzed by Western blotting and ELISA, respectively. HIF-1alpha 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. Dau significantly inhibited IGF-I-induced HIF-1alpha protein expression but had no effect on HIF-1alpha 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-1alpha and VEGF protein expression mainly by blocking the activation of PI-3K/AKT/mTOR signaling pathway. In addition, Dau reduced IGF-I-induced HIF-1alpha 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. Dau inhibits human breast cancer angiogenesis by suppressing HIF-1alpha protein accumulation and VEGF expression, which may provide a novel potential mechanism for the anticancer activities of Dau in human breast cancer.