Phospholipase D activity in human gastric carcinoma.

Growth factor-stimulated phospholipase D (PLD) catalyzes the hydrolysis of phosphatidylcholine, generating phosphatidic acid which may act as a second messenger during cell proliferation, therefore PLD is believed to play an important role in tumorigenesis. Thus we measured PLD activity in human gastric carcinoma to evaluate its role in gastric carcinogenesis. PLD activity was assayed by a unique transphosphatidylation reaction using microsomal fraction of 21 pairs of surgically resected human gastric carcinomas and adjacent noncancerous mucosas. The mean PLD activities in gastric carcinoma and adjacent noncancerous mucosa were 63.0 +/- 69.5, 44.2 +/- 60.1 pmol/min/mg, respectively (p < 0.01; Wilcoxon signed rank test). The mean ratio of PLD activity in gastric carcinoma and adjacent noncancerous mucosa was 1.63. This ratio was significantly higher in patients with larger tumors (> or = 5 cm) (p < 0.01; Mann-Whitney U-test). Our results indicate that the elevation of PLD activity plays an important role in the promotion of gastric carcinoma.