Measurement of glutathione S-transferase and its class-pi in plasma and tissue biopsies obtained after laparoscopy and endoscopy from subjects with esophagus and gastric cancer
Objectives: To develop an indirect enzyme-linked immunosorbent assay (ELISA) for measuring class-pi glutathione S-transferase (GST) in plasma, and tissue biopsies obtained from upper gastrointestinal cancer (UGI Ca) patients. Methods: GST activity and GST-pi concentration were detected in normal human squamous esophageal epithelium, normal gastric cardia and their corresponding malignant tumor biopsies. Results: Plasma GST was significantly higher (p < 0.05) in UGI Ca patients as compared to those obtained from normal individuals. Plasma GST-pi concentration in normal subjects was 6.6 +/- 1.9 ng/mg protein, whereas it was higher in UGI Ca patients (esophageal, 10.0 +/- 1.8; gastric, 10.7 +/- 1.7 ng/mL, p less than or equal to 0.01). GST and GST-pi levels were higher in surgically resected tumor biopsies as compared to normal tissues adjacent to a tumor (p < 0.05). GST-pi was also elevated in malignant esophagus and gastric biopsies taken at endoscopy as compared to normal and normal-appearing esophageal tissues (p < 0.05). Total GST was also increased significantly in gastric malignant tissues although its activity was within the same range in normal and normal-appearing tissues. A significant correlation between plasma GST-pi with that in malignant tissues was observed. Total GST and GST-pi were also correlated in different malignant tissues. Conclusions: Biopsies obtained at endoscopy can be used satisfactorily to measure tumor markers. (C) 2003 The Canadian Society of Clinical Chemists. All rights reserved.