Peroxiredoxins are capable of protecting cells from ROS toxicity and regulating signal transduction pathways OSI-027 mouse that use c-Abl, caspases, nuclear factor-kappaB (NF-κB), and activator protein-1 to influence cell growth and apoptosis. Evidence is fast growing

that oxidative stress is important not only for normal cell physiology but also for many pathological processes such as atherosclerosis, neurodegenerative diseases, and cancer [5–8]. Reactive oxygen species participate in carcinogenesis in all stages, including initiation, promotion, and progression [5] Levels of ROS such as O2 – are increased in Torin 2 breast cancer [9, 10]. The production of ROS accelerates tumor induction [11]. In vitro, Prx genes I-IV are overexpressed

when H2O2 concentration in cells is elevated [12]. Peroxiredoxin I, a cytosol form, is the most abundant and ubiquitously distributed member of the mammalian Prx family, and it has been identified in a large variety of organisms. It has been suggested that Prx I regulates cell proliferation and apoptosis by its interaction with oncogene products such as c-Abl. Peroxiredoxin I has been investigated in various human cancer samples as a potential marker. The reports cited above support that Prx I may be closely Pifithrin-�� in vitro associated with cancers. Nevertheless, the connection between Prx I and cancer has not yet been clearly defined. Elevated expressions of Prx I have been observed in several human cancers, including lung, breast, esophagus, oral, and thyroid [13–15]. In oral squamous cell cancer, Yanagawa et al. [15] found low levels of Prx I expression associated with larger tumor

masses, 3-mercaptopyruvate sulfurtransferase lymph node metastases, and poorly differentiated cancers. In contrast, Karihtala et al. [16] found no correlation between Prx I expression and clinicopathological features in breast cancer. Instead, levels of expression of Prxs III, IV, and V were significantly higher when breast cancers were poorly differentiated, suggesting their relationship to breast cancer. There are two major Prx subfamilies. One subfamily uses two conserved cysteines (2-Cys), and the other uses one cysteine (1-Cys) to scavenge H2O2 and alkyl hydroperoxides. Four mammalian 2-Cys members (Prx I-IV) use thioredoxin (Trx) as the electron donor for antioxidation [17]. Thioredoxin as an antioxidant protein is induced by various kinds of oxidative stresses [18–21]. Similar to Prxs, Trx plays an important role in regulating cancer cell growth, for example, by modulating the DNA binding activity of transcription factors, including nuclear factor-κB, p53, and glucocorticoid and estrogen receptors [22–25]. Thioredoxin may be closely associated with cancers. Immunohistochemical analysis using anti-Trx antibody has shown the expression of Trx in a number of human cancer tissues, including liver, colon, pancreas, and uterine cervix [26–28].