PTGS1 and neoplasm: Sales and Katz (2012) have shown that PGE2 biosynthesized by COX-1 and COX-2 in HeLa cells, increases expression of pro-angiogenic factors that can exert paracrine activity on endothelial cells to promote blood supply for tumor growth and alter vascular permeability for the release and distribution of leucocytes and macrophages to surrounding tissues.