Prostaglandin inactivation in the cytoplasm is carried out by the enzyme NAD(+)-linked 15 hydroxyprostaglandin dehydrogenase (15-PGDH); its expression and that of COX-2 are reciprocally regulated in cancer, thus both enzymes control the cellular levels of prostaglandins by opposing means (Tai et al., 2006; Tai, 2011). The gene discussed is PTGS2; the disease is cancer.