Analysis of cyclooxygenase expression in human colorectal adenomas

INTRODUCTION: Evidence from rodent intestinal tumorigenesis models suggests that both cyclooxygenase-1 and cyclooxygenase-2 may play important roles in the development and progression of human sporadic colorectal adenomas. However, previous studies of cyclooxygenase isoform expression in human colorectal adenomas have produced conflicting data. Cyclooxygenase-1 expression has been poorly studied, and cyclooxygenase-2 positivity of adenomas has been variable depending on the detection technique used. It also remains unclear whether villous adenomas express cyclooxygenase-2. METHODS: Cyclooxygenase isoform expression in human sporadic colorectal adenomas was analyzed by reverse transcription-polymerase chain reaction, Western blot analysis, and immunohistochemistry. RESULTS: Variable cyclooxygenase-1 expression was detected in all adenomas (n = 9) by both reverse transcription-polymerase chain reaction and Western blot analysis. Cyclooxygenase-2 expression was detected in eight (89 percent) of nine adenomas by reverse transcription-polymerase chain reaction and immunohistochemistry. Cyclooxygenase-2 protein was not detected by Western blot analysis in any adenoma. Cyclooxygenase-2 was expressed by all histopathologic types of adenoma and localized predominantly to superficial interstitial cells, in which it was associated with increased adenoma size. CONCLUSION: Cyclooxygenase-1 is expressed at variable levels by all adenomas. Cyclooxygenase-2 is expressed by the majority of adenomas, including those of the villous type, at levels below the sensitivity of Western blot analysis.