High molecular weight phospholipase A2 and fatty acids in human colon tumours and associated normal tissue

Human colon tumours usually form more prostaglandins (PGs) than associated normal tissues, but the mechanism(s) are not fully understood. We analysed fatty acid compositions, in particular arachidonate, and measured the amount and the activity of high molecular weight cytoplasmic phospholipase A2 (cPLA2) of these tissues. Total lipids extracted from homogenised surgical specimens were transesterified and fatty acids were analysed by gas chromatography. cPLA2 was separated by SDS-PAGE, Western-blotted, immunoblotted using a specific antibody to cPLA2 and semiquantified following enhanced chemiluminescence using a scanning densitometer. cPLA2 biological activity was also assayed using 1-stearoyl, 2-[1-14C]-arachidonyl, L-3-phosphatidylcholine. Compared with normal mucosa/submucosa, there was more total arachidonate in tumours (P < 0.01), and increased levels of cPLA2 occurred in 6 of 17 tumours. In conclusion, the higher amounts of tumour total arachidonate and the sometimes higher levels of cPLA2, might help to explain why some human colon tumours form increased amounts of PGs.