Even more striking, it was demonstrated that close structural analogues of celecoxib – devoid of any COX-2 inhibitory activity – were able to potently mimic all antitumour properties of celecoxib investigated so far, not just in vitro but also in various xenograft animal tumour models in vivo (Song et al, 2002; Kulp et al, 2004; Schönthal, 2006). This evidence concerns the gene PTGS2 and neoplasm.