Tumor-promoting and pro-angiogenic effects of roxarsone via VEGFR2/PLCγ/PKC signaling

Roxarsone is an organoarsenic feed additive used in livestock and poultry production that is released into the environment, where it poses a risk to human health. It is known to have a tumor-promoting effect that is brought about by pro-angiogenic factors such as vascular endothelial growth factor (VEGF) and it receptors (VEGFR). However, little information is available about the other signaling molecules that could be involved. This study aims to investigate the role of PLCγ/PKC signaling in roxarsone-induced angiogenesis in a mouse B16-F10 melanoma xenograft model and rat vascular endothelial cells (ECs). Results showed treatment with 5 mg/kg and 25 mg/kg roxarsone resulted in an obvious increase in the weight and volume of B16-F10 xenografts and PLCγ/PKC phosphorylation in a dose-dependent manner in C57BL/6 mice. SU5416, a VEGFR2 inhibitor, significantly attenuated the tumor growth induced by roxarsone. Further, 1.0 μmol/L roxarsone treatment in rat ECs was observed to significantly increase the optical density rate in the MTT assay, the number of BrdU-positive cells in the proliferation assay, the migration distance in the scratch test, and the number of meshes formed in the tube formation assay. In addition, treatment with 1.0 μmol/L roxarsone was associated with significantly higher phosphorylation of PLCγ/PKC than the control treatment. U73122, a PLCγ inhibitor, was found significantly to combat the effects of 1.0 μmol/L roxarsone on the ECs. Roxarsone is capable of promoting the growth of mouse B16-F10 xenografts and tube formation in vascular ECs. Moreover, VEGFR2/PLCγ/PKC signaling may play a regulatory role in in vivo and in vitro roxarsone-induced angiogenesis.