MnSOD Promotes Tumor Invasion via Upregulation of FoxM1–MMP2 Axis and Related with Poor Survival and Relapse in Lung Adenocarcinomas

Po-Ming Chen,Shwn-Huey Shieh,Yi-Hui Wu,Min-Chin Li,Chih-Yi Chen,Gwo-Tarng Sheu,Tzu-Chin Wu,Huei Lee,Ya-Wen Cheng

doi:10.1158/1541-7786.mcr-12-0527

Abstract

Manganese superoxide dismutase (MnSOD) is an antioxidant enzyme responsible for the elimination of superoxide radical. The role of MnSOD in tumor progression in different human cancers is still controversial. In the present study, MnSOD expression in lung cancer cells was explored by knockdown or overexpression using transfection of a short hairpin RNA (shRNA) or an expression vector, respectively, to determine whether MnSOD expression mediates lung cancer cell migration, invasion, and oncogenic potential by increasing FoxM1 and MMP2 expression. Western blotting showed that FoxM1 and MMP2 expression was dependent on MnSOD expression, suggesting that FoxM1 could be upregulated by MnSOD. Three FoxM1 promoters were constructed to verify this activation of FoxM1 by MnSOD and to determine the transcription factors responsible. Luciferase reporter and chromatin immunoprecipitation assays indicated that MnSOD overexpression in lung cancer cells promoted binding of E2F1 and Sp1 to their putative FoxM1 promoter-binding sites and activated FoxM1 reporter activity. MnSOD also enhanced the potential for cell migration, invasion, and anchorage-independent colony growth on soft-agar plates, again via upregulation of FoxM1 and MMP2 expression. In patients with lung cancer, evaluation of MnSOD expression in lung tumors by immunohistochemistry indicated a positive correlation between FoxM1 and MMP2 mRNA expressions. Kaplan-Meier and Cox regression analysis revealed a poorer overall survival (OS) and relapse-free survival (RFS) in patients with MnSOD-positive tumors than with MnSOD-negative tumors. We conclude that MnSOD may promote tumor aggressiveness via upregulation of the FoxM1-MMP2 axis, and that MnSOD expression can independently predict survival and relapse in patients with resected lung adenocarcinoma.

Highlights

The manganese superoxide dismutase (MnSOD) is an important antioxidant enzyme that eliminates superoxide radical (O2À) by converting it into H2O2 [1]
The potential association of MnSOD with MMP2 expression was evaluated by Western blot analyses of MnSOD and MMP2 protein expressions in 14 lung cancer cell lines
A positive correlation was indicated between MnSOD and the expression of both FoxM1 and MMP2 in different lung cancer cell lines, which suggested that the capability of lung cancer cells for invasion might be promoted via upregulation of FoxM1 and MMP2 by MnSOD

Summary

Introduction

The manganese superoxide dismutase (MnSOD) is an important antioxidant enzyme that eliminates superoxide radical (O2À) by converting it into H2O2 [1]. MnSOD may promote tumor progression in cancers, such as fibrosarcoma [9], gastric cancer [10, 11], glioblastoma [12], T-cell lymphoma [13], breast cancer [14, 15], cervical cancer [16], prostate cancer [17], and lung cancer [18]. Zhang and colleagues showed activation of MMP2 by MnSOD in human breast cancer MCF-7 cells via the regulation of intracellular reactive oxygen species A study on immunodeficient mice showed that MnSOD promoted the metastastic potential of fibrosarcoma cells via increased levels of MMP1 mRNA [22]. No connection has yet been established between MnSOD upregulation of MMP1 or MMP2 and the www.aacrjournals.org increased metastatic potential of MCF-7 and fibrosarcoma cells

Methods

Results

Conclusion