Induced oxidative stress and decreased expression of inducible heat shock protein 70 (ihsp 70) in patients with colorectal adenocarcinomas

Background: Colorectal cancer is one of the most common carcinomas observed in humans. Recently we have reported that increased oxidative stress is associated with human colorectal cancer. There are few and controversial studies on the clinical relevance of the expression of heat shock protein 70 (HSP 70), a member of the HSP family, in colorectal cancer. In this study, we assayed lipid peroxide levels, glutathione peroxidase (GPx) activity and the expression of inducible heat shock protein 70 (ihsp 70) in 20 paired samples of colorectal tumor and adjacent normal tissues in order to determine the relationship between oxidative stress and ihsp 70 expression. Histopathological results were also considered to estabish the clinical relevance of ihsp 70 in colorectal cancer. Methods: Malondialdehyde (MDA) levels as an indicator of lipid peroxidation and GPx activity were assayed by spectrophotometric methods. The Western blotting procedure was used for the determination of ihsp 70 expression. Results: Significant increases were observed in MDA levels (111%) and GPx activities (50%) of malignant tissues as compared with normal tissues of the patients with colorectal cancer. The expression of ihsp 70 was found to be decreased in malignant tissues as compared with normal tissues of the patients. Significant negative correlations were detected between MDA levels and ihsp expression (r = -0.516; P < 0.05) and GPx activity and ihsp 70 expression (r = -0.471; P < 0.05) in malignant tissues of patients. When the patients were grouped according to histopathological characteristics, no difference was found in MDA levels, GPx activity and ihsp 70 expression. Conclusion: Our results indicate that ihsp 70 expression is suppressed under induced oxidative stress conditions in malignant tissues of patients with colorectal cancer. Further research is needed to clarify the mechanisms responsible for this decrease and the definitive role of ihsp 70 in colorectal cancer.