Background-Experimental, clinical, and epidemiological studies have implica
ted mitogenic metabolites of arachidonic acid such as prostaglandin E-2 (PG
E(2)) in colorectal carcinogenesis. Recently, cyclooxygenase 2 (COX-2) whic
h catalyses the conversion of arachidonic acid to PGE(2), has displayed inc
reased levels in human colorectal cancer.
Aims-To evaluate whether there is differential COX-2 expression from differ
ent locations (caecum, ascending, transverse, descending, or sigmoid colon,
and rectum) in human colorectal cancer.
Methods-Protein levels of COX-2 were determined by western blot analysis in
tumours and adjacent normal mucosa of 39 patients with colorectal cancer.
Results-There was a notable overexpression of COX-2 protein in tumours loca
ted in the rectum (p<0.001) compared with other locations in the colon. Rec
tal tumours revealed elevated COX-2 protein levels in 18/20 cases compared
with 4/19 colonic cases. No association between enhanced COX-2 protein expr
ession in tumour tissue and Dukes's stages was found,
Conclusions/Results suggest that the differential COX-2 expression may be d
ue to differences in gene regulatory factors affecting COX-2 expression and
/or reflect secondary changes in tumour progression which may have clinical
implications.