Plasma thiols in prostate cancer.

Sir, We greatly appreciated one of the recently published article entitled Does plasma thiol and disulphide be a new marker for prostate cancer in prostate-specific antigen level between 10 and 20ng/mL by Topaktas et al. in your journal. The authors performed a prospective study investigating the plasma total thiol (TT), native thiol (NT), and disulfide (SS) levels as potential new biomarkers for the diagnosis of prostate cancer (PC), combining serum TT, NT, and SS levels with serum PSA measurements in 76 participants with elevated PSA levels ranging 0–20ng/mL, and further concluding that serum TT levels may help guide detecting PC, particularly with PSA levels between 10 and 20ng/ml [1]. However, we would like to kindly challenge some of the findings of the study as there seems to be confusing and conflicting parts as indicated below. As previously and generally shown in the literature, serum TT, NT, and SS levels were found to be significantly low in benign proliferative pathologies and cancer disease compared to healthy subjects and also shown to be independent predictors of poor survival [2,3]. In the present study, the authors found serum TT, NT, and SS levels higher in Group 1 than those of Group 2, with no significant difference. However, in the discussion part, they reported the following conclusion; “although not statistically significant, when PSA levels were between 10 and 20 (group 2), serum TT and NT levels were found to be high” as indicated by their own words in the manuscript. The results and conclusion appear to be discordant, hence having a likelihood of a huge confounder. How do the authors explain these inconsistent findings? One another important finding needs to be clarified is that authors have mentioned from a recent study [4] investigating the role of thiol/disulfide homeostasis in the differentiation of benign diseases from PC, which concluded that serum TT and NT levels were significantly higher in patients with PC than those found in patients with benign diseases. Of course, the literature can include various results; however, in order to support their results, the authors have cited another paper [5], which evaluated thiol/disulfide homeostasis prior to and 6months following radical prostatectomy in PC patients reporting that decreased TT and total antioxidant status levels weakened anti-oxidant defense mechanism in patients with PC, and further concluding that increased oxidative stress in PC patients may have a role in the etiopathogenesis of PC. However, the results of the two studies mentioned in the manuscript oppose to each other, hence need to be clarified. There are deficiencies in terms of Material – Method. The authors did not specify whether serum samples were obtained immediately by centrifugation and the Celcius degree to which they were stored. Moreover, another important point is that the researchers did not state whether they stored serum samples for the same period on average, according to the PSA groups because it is known that thiols are depleted over time, even in optimal storage conditions in vitro. Many thanks again for this scientific paper as providing significant contribution to the literature, but we kindly ask the authors, if possible, to enlighten us for the confusing parts in the study.