Biological significance of the production of membrane-associated phospholipase A2 in human gastric cancer

Abstract We examined the immunohistochemical expression of membrane-associated phospholipase A 2 (M-PLA 2 ), belonging to group II PLA 2 , in 44 advanced gastric cancers, using the ABC method and monoclonal antibody anti-human M-PLA 2 . M-PLA 2 mRNA was also examined in the same tumors by Northern blot analysis. In addition, the content of M-PLA 2 protein and prostaglandin E 2 (PGE 2 ) in the malignant lesion and in the non-malignant gastric mucosa was examined. The expression was detected in cancer cells in 31 out of 44 advanced gastric cancer tissues (70.4%) by the ABC method. M-PLA 2 mRNA was detected in 36 out of 44 gastric cancer tissues (81.8%), and the density was observed to be higher in tumor tissues than in the adjacent non-malignant gastric mucosa. The M-PLA 2 protein was detected both in malignant tissues and in non-malignant gastric mucosa, and the content of M- PL A 2 protein was significantly higher in malignant tissues than in the non-malignant gastric mucosa. There was a significant positive correlation between the expression of M-PLA 2 mRNA and the amount of M-PLA 2 protein. PGE 2 was also detected in the malignant tissues and in the non-malignant mucosa. The content of PGE 2 was significantly higher in the former. These results indicate that M-PLA 2 is produced both in malignant and non-malignant cells of the stomach, the former producing higher amounts of this enzyme than the latter. M-PLA 2 may be involved in cancer progression through its function or through the function of products of this enzyme's action such as PGE 2 in gastric cancer.