PTGS2 and esophageal cancer: Mercer et al. studied29 the effect of 5 flurouracil (5-FU) or 5-FU combination chemotherapy on COX-2 expression in biopsies from 14 esophageal cancers (obtained pre- and post-chemotherapy) and in tumour-derived cells exposed to 5-FU in vitro from a series of 44 cancers (breast, ovarian, esophageal and colonic cancers).