Importantly, compared to the control group that displayed an increased tumor vascularization, and extended tube-shaped framework, tumors from the As2O3-treated group showed a noticeably decreased number of blood vessels and vascular networks, as in the sorafenib-treated group, indicating decreased tumor angiogenesis as demonstrated by immunofluorescent CD31 staining. The gene discussed is PECAM1; the disease is neoplasm.