As2O3, a toxic traditional Chinese medicine, inhibited tumor growth and microvessel density by downregulating Notch pathway-related proteins Hes1, Dll4, and Notch1 in the small-cell lung cancer (SCLC) mouse model (2.5 and 5 mg/kg), and As2O3 restrained with the tube-forming ability of endothelial cells through the expression of Notch 1 and Hes1 in HUVECs (Yang et al., 2019a). Here, HES1 is linked to neoplasm.