Diagnostic value of thiols, paraoxonase 1, arylesterase and oxidative balance in colorectal cancer in human

Oxidative stress has been shown to play an important role in carcinogenesis. We hypothesize that serum oxidative and anti-oxidative factors work together to influence colon and rectal cancer through an oxidative balance mechanism. Total thiol (Ttl) is considered a plasma antioxidant and high density lipoprotein (HDL)- dependent paraoxonase 1 (PON1) is known as a free radical scavenger. This study was undertaken to determine the activity of PON1, arylesterase (ARE) and Ttl levels and oxidative balance in colorectal cancer (CRC) patients and healthy subjects. Paraoxonase and arylesterase activities of the HDL-dependent PON1 enzyme and the level of Ttl, total oxidant status (TOS),total antioxidant status (TAS) in forty patients with CRC (19 female, 21 male; mean age, 56.5 +/- 2.1) and thirty-nine age and sex matched healthy persons (22 female, 17 male; mean age 56 +/- 1.7) were studied. PON1 and ARE activities were significantly lower in patients with CRC compared to controls (p<0.001 for each), whereas oxidant parameters (TOS and OSI) were significantly higher in CRC patients (p<0.001 for each). However, TAS and Ttl significantly decreased in patients with CRC (p=0.03 and p<0.0001, respectively). According to the ROC curve analysis, Ttl was superior to other parameters in terms of diagnostic sensitivity and specificity which were 97.5% and 92.3%, respectively, and the AUC 0.97 in CRC patients. Decreased Ttl and HDL-dependent PON 1 enzyme activities and high TOS levels imply an imbalance of the free radical system which enhances the support the hypothesis that CRC is associated with excess reactive oxygen species. These findings show that of serum oxidative imbalance was associated with an increased risk of CRC. To our knowledge, this is the first report demonstrating lower serum PON1, ARE activities in CRC patients. The mechanism behind this association needs further elucidation.