ABSTRACT
FOXM1, a member of the Forkhead transcriptional family, plays an important role in the EMT process, and transforming growth factor-ß1 (TGF-ß1) has been identified as the most potent factor that can independently induce EMT in various types of cancer cells. Here we examine the important role of FOXM1 in TGF-ß1-induced EMT and investigate the mechanism underlying the relationship between TGF-ß1 and FOXM1. Lentivirus-mediated transfection was used to stably upregulate the expression of FOXM1, and a small interfering RNA (siRNA) was introduced to silence the expression of FOXM1. Transwell and wound-healing assays were then performed to assess the invasion and motility potential of non-small cell lung cancer (NSCLC) cells. The NSCLC cell lines exhibited EMT characteristics, including an elongated fibroblastoid shape, induced expression of EMT marker proteins, and increased migratory and invasive potential after induction with TGF-ß1. The overexpression of FOXM1 enhanced TGF-ß1-induced EMT in NSCLC cells. Knockdown of FOXM1 reversed TGF-ß1-induced EMT in NSCLC cell lines but had no effect on the phosphorylation level of ERK. Additionally, U0126, an ERK signaling inhibitor, exerted a reversible effect on TGF-ß1-induced EMT and inhibited FOXM1 expression. FOXM1 regulated by the ERK pathway can mediate TGF-ß1-induced EMT in NSCLC and is a potential target for the treatment of NSCLC.
Subject(s)
Carcinoma, Non-Small-Cell Lung/metabolism , Forkhead Transcription Factors/metabolism , Lung Neoplasms/metabolism , Biomarkers, Tumor/metabolism , Butadienes/pharmacology , Carcinoma, Non-Small-Cell Lung/pathology , Cell Line, Tumor , Cell Movement/genetics , Epithelial-Mesenchymal Transition/drug effects , Epithelial-Mesenchymal Transition/genetics , Forkhead Box Protein M1 , Forkhead Transcription Factors/genetics , Gene Expression Regulation, Neoplastic/drug effects , Humans , Lung Neoplasms/pathology , MAP Kinase Signaling System/drug effects , Molecular Targeted Therapy , Neoplasm Invasiveness/genetics , Nitriles/pharmacology , RNA, Small Interfering/genetics , Transforming Growth Factor beta1/metabolism , Transgenes/genetics , Wound Healing/geneticsABSTRACT
Forkhead box M1 (FOXM1), a member of the Fox family of transcriptional factors, is considered to be an independent predictor of poor survival in many solid cancers. However, the underlying mechanism is not yet clear. The aim of the present study was to investigate the clinical significance of the correlation between FOXM1 and epithelial-mesenchymal transition (EMT) in non-small cell lung carcinoma and the possible mechanism responsible for FOXM1-induced EMT and metastasis. In the present study, expression levels of FOXM1 and EMT indicator proteins were determined by tissue microarray (TMA) and immunohistochemical staining, western blotting and reverse transcription-PCR (RT-PCR). Other cellular and molecular approaches including gene transfection, small interfering RNA (siRNA), and migration and invasion assays were utilized. Our results demonstrated that FOXM1 overexpression was statistically significantly associated with a higher TNM stage (p=0.036), lymph node metastasis (p=0.009) and a positive smoking history of the patients (p=0.044). Additionally, high expression of FOXM1 correlated with loss of E-cadherin expression (p<0.001) and anomalous immunopositivity of Vimentin (p=0.002). Moreover, patient survival analysis demonstrated that high expression of FOXM1 (p=0.043) and the presence of lymph node metastasis (p=0.042) were independent prognostic factors for non-small cell lung cancer (NSCLC). Furthermore, various in vitro experiments indicated that overexpression or knockdown of FOXM1 expression altered EMT through activation or inhibition of the AKT/p70S6K signaling pathway. Collectively, the results suggest that FOXM1 may be used as a prognostic indicator for patients with NSCLC and promotes metastasis by inducing EMT of lung cancer cells through activation of the AKT/p70S6K pathway. Therefore, we suggest that FOXM1 may be a potential target for lung cancer therapy.