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Clin Cancer Res. 2001 Apr;7(4):824-30.

Elevated and altered expression of the multifunctional DNA base excision repair and redox enzyme Ape1/ref-1 in prostate cancer.

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Department of Pediatrics, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, 702 Barnhill Drive, Indianapolis, Indiana 46202, USA.


The DNA base excision repair pathway is responsible for the repair of cellular alkylation and oxidative DNA damage. A crucial step in the BER pathway involves the cleavage of baseless sites in DNA by an apurinic/apyrimidinic or baseless (AP) endonuclease (Ape1/ref-1), which is a multifunctional enzyme that acts not only as an AP endonuclease but also as a redox-modifying factor for a variety of transcription factors including Fos, Jun, paired box containing genes (PAX), nuclear factor-kappaB, hypoxia-inducible factor alpha (HIF-1alpha), HIF-like factor (HLF), p53, and others. The expression of Ape1/ref-1 in prostate has not been characterized previously. Ape1/ref-1 nuclear immunohistochemistry levels, scored for intensity as 1+, 2+, or 3+, were 91, 3, and 6% in benign hypertrophy (BPH), 0, 42, and 58% in prostatic intraepithelial neoplasia (PIN) and 3, 30, and 67% in prostate cancer, respectively, clearly showing an increase in Ape1/ref-1 nuclear staining in the PIN and cancer compared with BPH. Furthermore, the level of cytoplasmic staining of Ape1/ref-1 in cancer and PIN were elevated (42 and 36%, respectively) compared with BPH (5%). There was no correlation with prostate-specific antigen values or doubling times to Ape1/ref-1 levels. In conclusion, we have demonstrated that Ape1/ref-1 is dramatically elevated in prostate cancer, the level of staining of Ape1/ref-1 increases from low in BPH to intense in PIN and cancer, and there is an increase in the amount of Ape1/ref-1 in the cytoplasm of PIN and cancer compared with BPH. Given these results, we conclude that Ape1/ref-1 may be a diagnostic marker for early prostate cancer and play a role, through its repair, redox, or both functions, in the physiology of the early development of prostate cancer.

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