VEGFA and neoplasm: In an experimental HCC mouse model, down-modulation of HO-1 by siRNA resulted in increased cellular damage and apoptosis, thus reducing tumor growth.[5] Angiogenesis is well known as a crucial step in tumor growth and is regulated by angiogenic factors such as vascular endothelial growth factor (VEGF).[22,23] Furthermore, the HO-1 gene has responsive domains for many angiogenic agents and its expression induces neovascularization.[24,25] HO-1 also has a stimulatory effect on VEGF expression.[26]