Determination of erythrocyte Glutathione S-Transferase activity in individuals with gastric and colon cancer

Glutathione-S-Transferase (GST) in human cells has great importance in the detoxification mechanism of carcinogenic chemicals. Therefore, (GST) may be a useful tumor marker. This study examines whether GST activity in Gastric cancer (GC) and Colon Cancer (CC) is a helpful marker in diagnosing and monitoring the disease course. GST activity was investigated in patients with CC and GC and healthy individuals.

Erythrocyte isolation was performed in 3 ml blood samples from volunteers aged 18-75 years. Hemoglobin amounts were determined from the standard graph drawn by monitoring the conversion of methemoglobin to cyanmethemoglobin in the presence of cyanide at 540 nm. Glutathione S-transferase activity was determined by measuring the amount of enzyme that catalyzes 1 µmol of S-(2,4-dinitrophenyl) glutathione formed per minute using 1-Chloro-2,4-Dinitrobenzene. The mean values of GST activities of patients with CC and GC, respectively; (1.28 ± 0.23 U/gHb; 1.20 ± 0.30 U/gHb), were significantly higher when compared to the mean values of healthy individuals with GST activity (0.59 ± 0.13 U/gHb) (p < 0.05). The GST activity of patients with colon cancer, measured as (1.56 ± 0.13 U/gHb) after chemotherapy, was significantly higher than before (1.09 ± 0.12 U/gHb) (p < 0.05). GST activity measured as (1.53± 0.24 U/gHb) after chemotherapy in gastric cancer patients was significantly higher when compared to the value measured before chemotherapy (0.97± 0.12 U/gHb) (p < 0.05). Our results show that the change in GST activity in CC and GC can be used as a biomarker to monitor the disease course and response to chemotherapy.