PTGS2 and neoplasm: Data from studies that have looked at COX-2 expression and proliferation markers, such as Ki67, have shown a strong correlation between the presence of COX-2 and increased proliferation (Ferrandina et al, 2003; Boland et al, 2004), but as yet no data have been published to show that inhibition of COX-2 leads to a lower proliferative rate in tumours in vivo.