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Metastasis is an important cause of cancer-related death. Previous studies in our laboratory found that pregnane alkaloids from Pachysandra terminalis had antimetastatic activity against breast cancer cells. In the current study, we demonstrated that treatment with one of the alkaloid derivatives, (Z)-3β-ethylamino-pregn-17(20)-en (1), led to the downregulation of the HIF-1α/VEGF/VEGFR2 pathway, suppressed the phosphorylation of downstream molecules Akt, mTOR, FAK, and inhibited breast cancer metastasis and angiogenesis both in vitro and in vivo. Furthermore, the antimetastasis and antiangiogenesis effects of 1 treatment (40 mg/kg) were more effective than that of Sorafenib (50 mg/kg). Surface plasmon resonance (SPR) analysis was performed and the result suggested that HSP90α was a direct target of 1. Taken together, our results suggested that compound 1 might represent a candidate antitumor agent for metastatic breast cancer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Chiral ionone alkaloid ION-31a inhibits breast cancer metastasis and angiogenesis. • Its direct target was identified as HSP90α. • ION-31a downregulates HSP90/HIF-1α/VEGF/VEGFR2 pathway. Breast cancer has become the number one killer of women. In our previous study, an active compound, ION-31a, with potential anti-metastasis activity against breast cancer was identified through the synthesis of ionone alkaloid derivatives. In the present study, we aimed to identify the therapeutic target of ION-31a. We used a fluorescence tag labeled probe, molecular docking simulation, and surface plasmon resonance (SPR) analysis to identify the target of ION-31a. The main target of ION-31a was identified as heat shock protein 90 (HSP90). Thus, ION-31a is a novel HSP90 inhibiter that could suppress the metastasis of breast cancer and angiogenesis significantly in vitro and in vivo. ION-31a acts via inhibiting the HSP90/hypoxia inducible factor 1 alpha (HIF-1α)/vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) pathway and downregulating downstream signal pathways, including protein kinase B (AKT)/mammalian target of rapamycin (mTOR), AKT2/protein kinase C epsilon (PKCζ), extracellular regulated kinase 1/2 (ERK1/2), focal adhesion kinase (FAK), and mitogen-activated protein kinase 14 (p38MAPK) pathways. ION-31a affects multiple effectors implicated in tumor metastasis and has the potential to be developed as an anti-metastatic agent to treat patients with breast cancer. [ABSTRACT FROM AUTHOR]