Vascular
cyclooxygenase (COX)-2-dependent
prostacyclin (PGI(2)) may affect angiogenesis by preventing endothelial activation and platelet release of angiogenic factors present in platelet α-granules. Thus, a profound inhibition of COX-2-dependent PGI(2) might be associated with changes in circulating markers of angiogenesis. We aimed to address this issue by performing a clinical study with
celecoxib in
familial adenomatous polyposis (FAP). In nine patients with FAP and healthy controls, pair-matched for gender and age, we compared systemic biosynthesis of PGI(2),
thromboxane (TX) A(2), and
prostaglandin (PG) E(2), assessing their urinary enzymatic metabolites, 2,3-dinor-6-keto
PGF(1α) (PGI-M), 11-dehydro-TXB(2) (TX-M), and 11-α-hydroxy-9,15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic
acid (
PGE-M), respectively. The impact of
celecoxib (400 mg b.i.d. for 7 days) on
prostanoid biosynthesis and 14 circulating
biomarkers of angiogenesis was evaluated in FAP. Intestinal
tumorigenesis was associated with enhanced urinary TX-M levels, but unaffected by
celecoxib, suggesting the involvement of a COX-1-dependent pathway, presumably from platelets. This was supported by the finding that in cocultures of a human
colon adenocarcinoma cell line (HT-29) and platelets enhanced TXA(2) generation was almost completely inhibited by pretreatment of platelets with
aspirin, a preferential inhibitor of COX-1. In FAP,
celecoxib profoundly suppressed
PGE(2) and PGI(2) biosynthesis that was associated with a significant increase in circulating levels of most proangiogenesis
proteins but also the antiangiogenic
tissue inhibitor of metalloproteinase 2. Urinary PGI-M, but not
PGE-M, was negatively correlated with circulating levels of
fibroblast growth factor 2 and
angiogenin. In conclusion, inhibition of
tumor COX-2-dependent
PGE(2) by
celecoxib may reduce
tumor progression. However, the coincident depression of vascular PGI(2), in a context of enhanced TXA(2) biosynthesis, may modulate the attendant angiogenesis, contributing to variability in the chemopreventive efficacy of
COX-2 inhibitors such as
celecoxib.