PTGS1 and cancer: Although recent studies have shown that COX-1 may also play a role in carcinogenesis in some cancers, such as ovarian (Gupta et al, 2003), head and neck (Erovic et al, 2008) and colon cancer (Chulada et al, 2000), the common denominator in all these studies is an increase in the overall level of PGE2.