Quercetin inhibits angiogenesis by targeting calcineurin in the xenograft model of human breast cancer

Vascular endothelial growth factor receptor 2 (VEGFR2) mediated calcineurin/nuclear factor of activated T-cells (NFAT) pathway is crucial in the angiogenesis of human breast cancer. Quercetin (Qu), a flavonoid known to possess anti-angiogenesis and antitumor properties, inhibited calcineurin activity in vitro. Herein, we performed a study in vivo to evaluate the effects of Qu on the angiogenesis in breast cancer. Female BALB/c nude mice were injected with MCF-7 cells into the mammary fat and were randomly divided into four groups. The animals were treated with vehicle solution, tamoxifen (TAM, 5.6 mg/kg), tacrolimus (FK506, 3 mg/kg), or Qu (34 mg/kg) for 21 days, respectively. The results showed that, similar to TAM and FK506, Qu decreased tumor growth, limited oncocyte proliferation and promoted tumor necrosis. Anti-angiogenic actions of Qu were demonstrated as decreased serum VEGF (P<0.01), and sparse microvessel density (P<0.05). Qu significantly inhibited tumor calcineurin activities, and the inhibitory rate was 62.73% in Qu treated animals, compared to that was 72.90% in FK506 group (P>0.05). Effects of Qu on calcineurin/NFAT pathway were confirmed as decreased subcellular located levels of VEGF (P<0.05), VEGFR2 (P<0.05) and NFATc3 (P<0.01), downregulated gene expression of VEGF (P<0.05), VEGFR2 (P<0.05) and NFATc3 (P<0.01), reduced protein levels of VEGF (P<0.05), VEGFR2 (P<0.05), and NFATc3 (P<0.01) in tumor tissues. These findings indicate that Qu inhibit angiogenesis of human breast cancer xenograft in nude mice, which was associated with suppressing calcineurin activity and its regulated pathway activation.