Numerous studies have shown a link between COX-2/PGE2 and Wnt/β-catenin signaling in development of many cancers, including lung cancer (Singh and Katiyar, 2013), skin cancer (Prasad and Katiyar, 2014), breast cancer (Tu et al., 2014), colorectal cancer (Castellone et al., 2005), and neuroblastoma (Jansen et al., 2015). Here, PTGS2 is linked to breast cancer.