Cytosolic phospholipase A2, cyclo-oxygenases and arachidonate in human stomach tumours.

Abstract Human stomach tumours usually form more prostaglandins (PGs) than their associated normal mucosa/submucosa, but the mechanisms are not fully understood. The key enzymes are cytosolic phospholipase A 2 (cPLA 2 , Mr 85000) and the cyclo-oxygenases (COXs) which exist in constitutive (COX-1) and inducible forms (COX-2). In human stomach tumours and associated macroscopically normal tissues, we determined the fatty acid composition by gas chromatography, amounts of cPLA 2 , COX-1 and COX-2 by immunoblotting with specific antibodies and cPLA 2 enzyme activity using a tritiated substrate. Although compared to normal mucosa there was less arachidonate in tumours ( P 2 and COX-1 and cPLA 2 activity were similar in tumours and normal mucosa. However, substantial amounts of COX-2 were found in the tumours but not in the mucosa, which may explain why many gastric tumours form increased amounts of PGs. © 1997 Elsevier Science Ltd.