Measurement of glutathione S-transferase and its class-π 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-π glutathione S-transferase (GST) in plasma, and tissue biopsies obtained from upper gastrointestinal cancer (UGI Ca) patients. Methods GST activity and GST-π 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-π 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 ≤ 0.01). GST and GST-π levels were higher in surgically resected tumor biopsies as compared to normal tissues adjacent to a tumor (p< 0.05). GST-π 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-π with that in malignant tissues was observed. Total GST and GST-π were also correlated in different malignant tissues. Conclusions Biopsies obtained at endoscopy can be used satisfactorily to measure tumor markers.