Introduction Barrett's oesophagus (BO) is a premalignant condition for oesophageal adenocarcinoma, an increasingly common malignancy with poor survival. The prostanoids and leukotrienes are lipid inflammatory mediators derived from a common precursor by the cyclooxygenase (COX) and 5-lipoxygenase (5-LO) pathways respectively. Both families have been implicated in oesophageal adenocarcinoma, prompting studies of the effects on disease progression of drugs that modulate these pathways. NSAIDs may prevent tumorigenesis by inhibiting COX, but are also a risk factor for reflux and Barrett's disease. Increased expression of 5-LO pathway proteins is implicated in oesophageal adenocarcinoma, so we hypothesised that in vitro exposure of oesophageal tissue to an NSAID may induce transcriptional expression of genes for 5-LO pathway enzymes.
Methods Patients with known BO (n=14) were recruited as they attended endoscopy for routine surveillance. There was no evidence of dysplasia before or after this endoscopy. In each patient, oesophageal biopsies were taken from a single level of BO and from proximal squamous mucosa. Biopsies from each site were cultured for 15 h at 37°C in HEPES-buffered DMEM in the presence or absence of indomethacin (10 μM). Biopsies were then transferred to lysis buffer for quantification of mRNA for 5-LO, FLAP, LTA4 hydrolase and LTC4 synthase using quantitative RT-PCR. Transcript levels for each enzyme were calculated as mean ∆∆Ct values compared to baseline expression after correction with a calibration sample across all plates.
Results Culture with indomethacin (10 μM, 15 h) significantly increased transcriptional expression of 5-LO (p<0.01) and FLAP (p<0.05) in squamous control biopsies, with a trend for increased LTC4 synthase transcripts (p=0.08) but not LTA4 hydrolase (p=0.38), suggesting induction of a cysteinyl-leukotriene biosynthetic pathway. Expression of the 5-LO pathway genes was elevated at baseline in Barrett's tissues and in vitro exposure to indomethacin did not produce further changes in this group (all p>0.2).
Conclusion These results indicate that indomethacin increases transcriptional expression of the proximal, rate-limiting enzymes of the 5-LO pathway in squamous oesophageal tissues, which may lead to increased enzyme activity and production of tumorigenic leukotrienes. This preliminary study suggests that brief NSAID exposure in vitro may mimic changes in the expression of 5-LO pathway genes induced in vivo in Barrett's metaplasia.
Competing interests None declared.
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