Cytoplasmic Ape1 Expression Elevated by p53 Aberration May Predict Survival and Relapse in Resected Non-Small Cell Lung Cancer

Abstract

Subcellular localization of apurinic/apyrimidinic endonuclease-1/redox factor-1 (Ape1) has been demonstrated to promote lung tumor malignancy via NF-κB activation. We hypothesized that increased cytoplasmic Ape1 expression might cause NF-κB activation by p53 aberration, and result in poor outcome in non-small cell lung cancer (NSCLC). Herein, knockdown of E6 or p53 and overexpression of E6 were performed in various lung cancer cells to test whether cytoplasmic Ape1 expression could be elevated by p53 aberration. To examine whether cytoplasmic Ape1 could be associated with patients' outcome, 125 lung tumors from patients with NSCLC were collected to determine Ape1 protein and mRNA expression by immunohistochemistry and real-time RT-PCR. Our data showed that cytoplasmic Ape1 decreased in E6-knockdown TL-1 cells and increased in E6-overexpressed TL-4 and p53-knockdown H520 cells; and cell invasion capability was dependent on the presence of cytoplasmic Ape1. Increases in cytoplasmic Ape1 by p53 aberration may be through activation of Ape1 transcription and S-nitrosation of Ape1 protein. Kaplan-Meier and Cox models showed that patients with high cytoplasmic Ape1 had shorter cancer-specific survival (CSS) and relapse-free survival (RFS) periods than did those with low cytoplasmic Ape1. We suggest that cytoplasmic Ape1 expression elevated by p53 aberration may be used to predict poor survival and relapse in patients with NSCLC.