Increased Glutathione Reductase Expression and Activity in Colorectal Cancer Tissue Samples: An Investigational Study in Mashhad, Iran

Abstract

Background: Glutathione reductase is an important enzyme in oxidative metabolism that provides reduced glutathione from its oxidized form in the cells. The role of oxidative stress in tumor tissues has led us to investigate the gene expression and activity of this enzyme in tumor and adjacent resected margins of colorectal cancer tissues, one of the most common malignancies in humans. Methods: We conducted this study on 15 Iranian colorectal cancer patients. RNA was extracted from fresh colon tissues that included tumor and anatomically normal margin tissue. Expression of the glutathione reductase gene was determined using realtime PCR by the ΔΔCt relative quantification method. The gene expression results were standardized with glyceraldehyde 3-phosphate dehydrogenase as the endogenous reference gene. In addition, we measured enzyme activity of glutathione reductase with a commercial kit based on a colorimetric assay. Results: The tumor tissue had higher expression of glutathione reductase compared to the margin tissue (P=0.005). There was significantly greater glutathione reductase enzyme activity in the tumor tissue (116.9±34.31 nmol/min/ml) compared to the noncancerous adjacent tissues (76.7±36.85 nmol/min/ml; P=0.003). Conclusion: These data showed increased glutathione reductase expression and enzyme activity in colorectal tumor tissue. Given the key role of glutathione in synthesis of dNTPs for DNA repair with the glutaredoxin system, the increased glutathione reductase expression and activity might be a reflection of hyperactivity of this enzyme in DNA synthesis and the repair process in colorectal cancer cells.

Keywords

• Colorectal cancer
• Glutathione reductase
• Oxidative stress
• Real-time PCR