PTGS2 and colonic neoplasm: Secondary BAs, such as DCA, initiate proliferation and invasion of colon cancer cells through activation of COX-2, epidermal growth factor receptor (EGFR), extracellular signal-regulated kinases 1 and 2 (ERK1/2), activator protein 1 (AP1), c-Myc, and NF-kB at very low concentration [98].