The VEGFR2/mTOR/S6K1 pathway involved in the angiogenic effects of roxarsone in vitro and in vivo.

Roxarsone, an organoarsenic compound used in poultry industry to increase weight gain, is widely used as a feed additive in some developing countries. Roxarsone has a low absorption rate and is mostly excreted with feces, which could pose a risk to human health through environmental and animal food routes. Roxarsone has been demonstrated to have tumor-promoting and proangiogenic effects. Herein, we report the role of VEGFR2/mTOR/S6K1 signaling in roxarsone-promoted vessel endothelial cell growth and angiogenesis in the Matrigel plug model and the mouse B16 cell tumor transplantation model. In angiogenesis-related experiments in vitro, 1.0 μM roxarsone significantly increased the activity, proliferation, migration, and tube formation of rat vascular endothelial cells. In addition, 1.0 μM roxarsone upregulated the protein levels of mTOR, phosphorylated mTOR, S6K1, and phosphorylated S6K1 and significantly increase the expression of Mtor and S6k1 mRNA. Rapamycin and SU5416 significantly inhibited the effects of 1.0 μM roxarsone on cell growth. Furthermore, the weight, volume, and CD31 expression of B16-F10 xenografts and Matrigel plugs in mice were upregulated by 25 mg/kg roxarsone. The protein and mRNA levels of mTOR, S6K1 and its phosphorylated protein were significantly increased in the roxarsone treatment group in xenografts. SU5416 and a short hairpin RNA targeting Vegfr2 significantly reduced roxarsone-promoted xenograft and Matrigel plug growth. In summary, this study indicated that the VEGFR2/mTOR/S6K1 signaling plays a regulatory role in roxarsone-mediated promotion angiogenesis and enhanced tumor growth.