Functional characterization of a promoter polymorphism in APE1/Ref‐1 that contributes to reduced lung cancer susceptibility

Apurinic/apyrimidinic endonuclease 1/redox effector factor‐1 (APE1/Ref‐1) is a ubiquitous multifunctional protein that possesses both DNA‐repair and redox regulatory activities. Although it was originally identified as a DNA‐repair enzyme, accumulating evidence supports a role of APE1/Ref‐1 in tumor development. To investigate association between APE1/ Ref‐1 polymorphisms and lung cancer risk in Chinese populations, we first genotyped three variants of APE1/ Ref‐1 and found a ‐141 T‐to‐G variant (rs1760944) in the promoter associated with decreased risk of lung cancer [odds ratio (OR) = 0.62 for GG;P=0.043]. Similar results were obtained in a follow‐up replication study. Combined data from the two studies comprising a total of 1072 lung cancer patients and 1064 cancer‐free control participants generated a more significant association (P= 0.002). We observed lower APE1/Ref‐1 mRNA levels in the presence of the protective G allele in human peripheral blood mononuclear cells and normal lung tissues. The ‐ 141G‐allele‐promoter construct exhibited decreased luciferase reporter gene expression. Electrophoretic mobility shift assays and surface plasmon resonance analysis showed that the — 141G allele impaired the binding affinity of some transcription factor, accounting for lower APE1/Ref‐1‐promoter activity. Supershift assays further revealed that the protein of interest was octamer‐binding transcription factor‐1 (Oct‐1). Chromatin immunoprecipitation reconfirmed binding of Oct‐1 to the APE1/Ref‐1 — 141‐promoter region. We also found that Oct‐1 conferred attenuated transactivation capacity toward the — 141G variant by exogenously introducing Oct‐1. These data indicate that genetic variations in APE1/Ref‐1 may modify susceptibility to lung cancer and provide new insights into an unexpected effect of APE1/Ref‐1 on lung carcinogenesis.—Lu, J., Zhang, S., Chen, D., Wang, H., Wu, W., Wang, X., Lei, Y., Wang, J., Qian, J., Fan, W., Hu, Z., Jin, L., Shen, H., Huang, W., Wei, Q., Lu, D. Functional characterization of a promoter polymorphism in APE1/Ref‐1 that contributes to reduced lung cancer susceptibility. FASEB J. 23, 3459–3469 (2009). www.fasebj.org