Abstract 1867: Application of oxylipin metabolomics to a celecoxib intervention in men at risk for colorectal neoplasia recurrence

Abstract

Abstract Background. In randomized controlled trials, non-steroidal anti-inflammatory agents (NSAIDs) have been shown to prevent the development of colorectal adenoma (CRA) by 15-40% depending on the agent, dose and duration of exposure. Toxicity concerns limit the acceptability of these agents for general use in the population, particularly for COX2 selective agents such as celecoxib. COX2 metabolizes arachidonic acid (AA) to the pro-inflammatory prostaglandins (PGs); an established pathway in CRA development. AA is also metabolized by cytochrome P450 (CYP450) and lipoxygenase (LOX) enzymes to produce other biologically active metabolites called oxylipins that mediate pain, hypertension, and other physiologic functions. Methods. In 2001, we initiated a randomized phase III clinical trial to evaluate the chemopreventive effect of the COX2 inhibitor celecoxib in individuals at risk for CRA. In a subset of participants (N=126 men and N=59 women) who received celecoxib or placebo for a minimum of 12 months, we performed plasma oxylipin profiling analysis using HPLC coupled to a 4000 QTRAP mass spectrometer (MS). Fasting plasma samples for this ancillary study were collected at the one-year clinic visit and immediately stored at -80C at collection. These samples have never undergone prior freeze-thaw. Once thawed, triphenylphosphine (TPP) and butylated hydroxytoluene (BHT) (0.2% w/w) were added to preserve the oxylipins. Plasma samples (250 µL) were subjected to solid phase extraction before analysis as described previously (Liu et al 2009). Results. Using HPLC-MS, we were able to separate and quantify 89 oxylipins (CV's <30%). On average, the levels of the COX2 metabolite and primary target of the intervention, prostaglandin E2 (PGE2), were non-significantly lower (23%) in the celecoxib treated individuals when compared to placebo (P=0.20). The 5-LOX metabolite, 5-HETE (inducer of pulmonary vasoconstriction and edema) was higher in the celecoxib group (P=0.033) whereas CYP450 metabolites: 8,9-DiHETrE (P=0.018), 11,12-DiHETrE (P=0.053), 16,17-DiHDPE (P=0.059) and 10,11-DiHDPE (P=0.040) - associated with hypertension - were higher in the celecoxib treated individuals when compared to placebo. Conclusions. Upregulation of COX2 (and subsequent production of pro-inflammatory PGE2) is a well-established mechanism in the pathogenesis of colorectal cancer, and thus an attractive chemoprevention target. Our results suggest that CYP450 and LOX metabolites increase in celecoxib treated subjects, when compared to placebo, while achieving only modest inhibition of COX2 dependent PGE2. These findings suggest that selective perturbation of the AA metabolic pathway may induce the P450 and LOX metabolism of AA resulting in increased levels of potentially harmful oxylipins. Preliminary analyses of the relationship between oxylipins, CRA and toxicity outcomes in this sub-study by treatment status will be presented. Citation Format: Jessica Anne Miller, Jun Yang, Bruce Hammock, Peter Lance, Erin Ashbeck, Patricia A. Thompson. Application of oxylipin metabolomics to a celecoxib intervention in men at risk for colorectal neoplasia recurrence. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1867. doi:10.1158/1538-7445.AM2014-1867