Background: Cyclooxygenase enzymes (COX-1, COX-2, and COX-3) convert arachidonic acid to prostaglandins, prostacyclins, thromboxanes, and other hydroxy fatty acids. Among these, prostaglandin E(2) (PGE(2)) has tumor growth-promoting activity. The COX-2 isoform is the primary enzyme involved in PGE(2) production in cancerous tissue.
Objective/hypothesis: We administered the COX-2 inhibitor celecoxib (200 mg b.i.d.) to women at increased breast cancer risk. Our hypothesis was that PGE(2) would be secreted in breast nipple aspirate fluid (NAF), that levels in NAF would be higher than in corresponding plasma, and that celecoxib would decrease PGE(2) levels in NAF (reflecting a decreased breast tissue eicosanoid production) and plasma.
Specific aim: To determine if PGE(2) concentrations in NAF and plasma decrease after a 2-week course of celecoxib and then return to baseline 2 weeks after stopping the medication (washout).
Study design: NAF and plasma were collected before celecoxib treatment, 2 weeks after taking celecoxib, and 2 weeks after washout. Each woman served as her own control.
Results: PGE(2) concentrations in NAF and plasma were detectable in samples using two measurement techniques. On average, NAF PGE(2) levels were 81-fold higher in NAF than in matched plasma. Technically, there were differences in PGE(2) concentrations measured in similar fluids depending on the assay technique used (RIA versus chemiluminescence immunoassay). There were no significant decreases in PGE(2) concentrations after celecoxib administration.
Conclusions: PGE(2) can be measured in NAF. PGE(2) levels are concentrated in NAF when compared with matched plasma samples. Celecoxib 200 mg b.i.d. does not appear to significantly decrease PGE(2) concentrations in NAF and plasma.