Early expression of cyclo-oxygenase-2 during sporadic colorectal carcinogenesis

J Pathol. 1999 Feb;187(3):295-301. doi: 10.1002/(SICI)1096-9896(199902)187:3<295::AID-PATH254>3.0.CO;2-Y.


Regular administration of non-steroidal anti-inflammatory drugs (NSAIDs) may reduce the incidence of colorectal cancer by targeting cyclo-oxygenase-2 (Cox-2), a key enzyme in arachidonic acid metabolism. To evaluate the role of Cox-2 in sporadic colorectal cancer development, Cox-2 expression was investigated by immunohistochemistry in 85 adenomas, 53 carcinomas, 34 hyperplastic lesions and 104 samples of histologically normal mucosa adjacent to adenoma or carcinoma. In addition, Cox-2 mRNA expression was assessed by reverse transcription-polymerase chain reaction (RT-PCR) in six adenomas and 14 carcinomas with paired grossly normal mucosa. Immunohistochemistry for the proliferation-associated antigen Ki-67 and in situ end labelling for demonstrating apoptotic bodies were also used to analyse the associations between Cox-2 expression and proliferation and apoptosis. Cox-2 protein expression was increased in 76/85 (89.4 per cent) adenomas and 44/53 (83.0 per cent) carcinomas compared with normal mucosa. Cox-2 protein expression was unrelated either to the degree of dysplasia or to the size of the adenomas (p > 0.50, p > 0.10, respectively) or to differentiation, Dukes stage or lymph node metastasis of carcinomas (all p > 0.50). Interestingly, 20/34 (58.8 per cent) hyperplastic lesions adjacent to adenomas or carcinomas displayed expression higher than in normal mucosa (18.3 per cent) (p < 0.0001) but lower than in adenomas or carcinomas (p < 10(-5), p < 0.001, respectively). There were no correlations between Cox-2 protein expression and proliferative or apoptotic index in either adenomas or carcinomas (all p > 0.25). Cox-2 mRNA expression was significantly increased in adenomas and carcinomas compared with normal mucosa (p < 0.005, p < 0.001, respectively). There were no differences between adenomas and carcinomas in either protein or mRNA levels (p > 0.25, p > 0.90, respectively). These data indicate that enhanced expression of Cox-2 occurs early during colorectal carcinogenesis and may contribute to tumour formation.

MeSH terms

  • Adenoma / enzymology
  • Cell Transformation, Neoplastic / metabolism*
  • Colorectal Neoplasms / enzymology*
  • Cyclooxygenase 2
  • Disease Progression
  • Gene Expression
  • Humans
  • Immunoenzyme Techniques
  • In Situ Nick-End Labeling
  • Intestinal Mucosa / enzymology
  • Isoenzymes / metabolism*
  • Membrane Proteins
  • Peroxidases / metabolism*
  • Prostaglandin-Endoperoxide Synthases / metabolism*
  • RNA, Messenger / genetics
  • RNA, Neoplasm / genetics
  • Reverse Transcriptase Polymerase Chain Reaction


  • Isoenzymes
  • Membrane Proteins
  • RNA, Messenger
  • RNA, Neoplasm
  • Peroxidases
  • Cyclooxygenase 2
  • PTGS2 protein, human
  • Prostaglandin-Endoperoxide Synthases