CD34 and neoplasm: The CD34 immunohistochemical staining, average optical density (AOD) statistics by ImageJ software (Fig. 7a,b), and western blot analysis of VEGF and Flk1 (Fig. 7c,d) in the B16F10 xenografts indicated that roxarsone could promote tumor angiogenesis, an important process in the development of most tumors, and might further explain the co-carcinogenicity of roxarsone.