PTGS2 and melanoma: Particularly, increased expression of PG-endoperoxide synthase 2 (PTGS2) also known as cyclooxygenase-2 (COX-2), and its major metabolite PGE2 has been observed in many different types of cancer including melanoma (Becker et al., 2009; Wang and Dubois, 2010; Ko et al., 2017).