Expression of peroxiredoxin and thioredoxin in human lung cancer and paired normal lung

Background: Peroxiredoxins (Prxs) have been implicated in regulating many cellular processes including cell proliferation, differentiation and apoptosis. However, the pathophysiological significance of Prx proteins, especially in lung disease, has not been defined. Therefore, the authors investigated the distribution and expression of various Prx isoforms in lung cancer and compared this with normal lung from human and mouse. Methods: Patients diagnosed with lung cancer who underwent surgery at Ajou Medical Center were enrolled. Expression of Prxs, thioredoxin and thioredoxin reductase was analysed by proteomic techniques. Immunohistochemistry was performed to localize Prx proteins. Results: Immunohistochemical staining showed that the isoforms of Prx I, II, III and V were predominantly expressed in bronchial and alveolar epithelium as well as in alveolar macrophages of the normal mouse lung. The isoforms I, III and thioredoxin were overexpressed in lung cancer tissues compared with normal lungs. There was also an increased amount of oxidized form of Prx I and a putative truncated form of Prx III in lung cancer samples when analysed on two‐dimensional electrophoresis. In addition, a 40‐kDa intermediate MW protein band and high MW bands of over 20 kDa, recognized by anti‐Prx (a‐Prx) I antibody, were present in tissue extracts of lung cancer patients on one‐dimensional electrophoresis. Conclusion: The upregulation of Prx I, Prx III and thioredoxin in lung cancer tissue may represent an attempt by tumour cells to adjust to the microenvironment in a manner that is advantageous to survival and proliferation.