Gleason scores 3+3 to 3+4 is intermediate PCa grade 3 with a secondary pattern of grade 3 or 4 4. to intermediate grade PCa (Gleason scores 3+3 to 3+4) or BN tissues. PrxsSO3 were increased in high grade PCa. Oxidized Trx1 and PrxsSO3 are indicators of oxidative stress. To study whether redox imbalance may potentially affect enzyme activities of antioxidant proteins (AP), we decided levels of selected AP in PCa tissues by western blot analysis and found that mitochondrial manganese superoxide dismutase (MnSOD), Prx 3, and Trx1 were increased in high grade PCa tissues when compared with BN tissues. Enzyme activities of MnSOD in high grade PCa tissues were significantly increased but at a lower magnitude when compared with the levels of MnSOD protein (0.5 folds vs. 2 folds increase). Trx1 activity was not changed in high grade PCa tissues despite a large increase in Trx1 protein expression. Further studies demonstrated a significant increase in posttranslational modifications of tyrosine and lysine residues in MnSOD protein and oxidation of Cys at active site (Cys 32 and Cys 35) and regulatory site (Cys 62 and Cys 69) of Trx1 in high grade PCa compared to BN tissues. These discordant changes between protein levels and AGN 205327 enzyme activities are consistent with protein inactivation by redox imbalance and/or posttranslational modifications. In contrast, the protein level and activity of extracellular superoxide dismutase (ECSOD) were significantly decreased in high grade PCa when compared with adjacent BN tissues. Results from cell lines mirror those from PCa tissues. Knowledge of redox state profiles in specific cancers may help to predict the behavior and response of each malignancy to chemotherapeutic drugs and radiation. Keywords:ECSOD, MnSOD, Prx, Trx1, prostate cancer, posttranslational modifications, redox balance == Introduction == Alteration of redox status is an important feature of carcinogenesis and has been exploited therapeutically in the treatment of cancer. For example, cancer cells are frequently in oxidative stress conditions as exhibited by higher levels of intracellular reactive oxygen species (ROS), increased hydrogen peroxide (H2O2) release as well as being susceptible to prooxidant-induced AGN 205327 cell death [1-3]. Radiation and many other therapeutic brokers such as doxorubicin or mitomycin C may exhibit their cancer killing effects by increased ROS production, pushing already stressed malignancy cells beyond their limits of tolerance [4-5]. On the other hand, up-regulation of antioxidant enzymes has been frequently detected in cancers and has been suggested to confer resistance of cancer cells to ROS-generating therapeutic brokers [6]. These contradictory results emphasize the importance of defining the redox state of each type of cancer. Prostate cancer (PCa) is the most common and second leading cause of cancer deaths of men in the USA. Previous studies in our laboratory have exhibited an increase in oxidative/nitrative damage in human PCa tissues and cells [7-8], implicating a role of oxidative stress in cancer development. In addition, we exhibited that intra-and extracellular redox says were altered in aggressive PCa cells [9-10] and subsequently regulated PCa cell behavior [11]. It is increasingly acknowledged that subcellular redox systems have distinct functions and are subject to impartial regulation [12]. The redox status of proteins involved in the transmission of redox signals in distinct suborganelles such as thioredoxin 1(Trx1), peroxiredoxin(s) (Prxs), manganese superoxide dismutase (MnSOD), or extracellular superoxide dismutase (ECSOD) have not been previously studied in human PCa tissues. Trx1 is usually Rabbit Polyclonal to NSF a redox modulating protein, providing reducing equivalents to numerous redox-sensitive proteins, such as ribonucleotide reductase [13] and redox-related transcriptional factors [6]. Trx1 contains five cysteine residues and reduces target proteins using its two vicinal cysteine (Cys) residues (Cys32 and Cys35) in the active site, where the molecule itself becomes oxidized, forming an intramolecular disulfide bond. Further oxidation of Trx1 results in the formation of a second intramolecular disulfide bond between Cys62 and Cys69, and then an intermolecular disulfide bond between Cys73 of two different Trx1 molecules [14]. Our previous study using PCa cell lines suggested that Trx1 redox says may function as a biomarker of redox imbalance and play an important role in modulating the response of PCa cells to prooxidant treatments [15]. One AGN 205327 of the Trx1-target.