Background:　Breast　cancer　is　the　most　common　female　cancer　worldwide.　Large　hypoxic　area　is　one　of　the　features　of　tumor　microenvironment.　Highly　activated　hypoxia-induced　pathways　positively　correlate　with　poor　clinical　response　to　chemo-　and　radiotherapy　and　high　mortality　in　breast　cancer　patients.　Purpose:　We　explore　the　effect　of　sanguinarine　on　hypoxia-induced　activation　of　Ephrin　type-B　receptor　4　(EphB4)　and　hypoxia　inducible　factor-1　alpha　(HIF-1　alpha)　pathways　in　breast　cancer.　Results:　Hypoxia-induced　expression　of　a　receptor　tyrosine　kinase　EphB4　was　observed　in　hypoxic　breast　cancer　cell　models.　Sanguinarine,　a　natural　alkaloid,　could　effectively　combat　hypoxia-induced　EphB4　and　HIF-1　alpha　expression.　Sanguinarine　inhibited　the　activation　of　downstream　protein　signal　transducer　and　activator　of　transcription-3　(STAT3),　thereby　blocking　hypoxia-induced　HIF-1　alpha/STAT3　interaction　and　downregulating　the　mRNA　levels　of　their　target　genes.　Mechanically,　sanguinarine　attenuated　HIF-1　alpha　protein　levels　via　inhibition　of　MAPK/ERK　pathways　and　promotion　of　HIF-1　alpha　proteasome　degradation.　Sanguinarine　inhibited　STAT3　activation　through　targeting　its　upstream　EphB4　and　accelerating　STAT3　dephosphorylation.　Correspondingly,　xenograft　models　confirmed　that　sanguinarine　treatment　disrupted　hypoxia-induced　pathways　and　inhibited　tumor　growth　in　vivo.　Conclusions:　Our　results　may　bring　insights　to　the　hypoxia-induced　pathways　in　breast　cancers,　and　suggest　sanguinarine　as　a　promising　candidate　for　EphB4　and　HIF-1　alpha-targeted　inhibition.