Overexpression of Krüppel-like factor 4 suppresses migration and invasion of non-small cell lung cancer through c-Jun-NH2-terminal kinase/epithelial-mesenchymal transition signaling pathway

Krüppel-like factor 4 (KLF4) is a transcription factor and plays a vital role in cancer initiation and development. However, the role of Krüppel-like factor 4 in the metastasis of non-small cell lung cancer (NSCLC) is not clear. Here, we demonstrated that the expression of Krüppel-like factor 4 was significantly decreased in human non-small cell lung cancer tissues compared with that in normal tissues using Western blot. We performed immunohistochemical staining and observed the decreased expression of Krüppel-like factor 4 in human lung cancer tissues, and metastatic tumor tissues located in the trachea and main bronchus. We also found that the E-cadherin expression was decreased, while vimentin expression was increased in human NSCLC tissues and metastatic tumor tissues located in the trachea and main bronchus. Additionally, enforced expression of Krüppel-like factor 4 in mouse lungs significantly inhibited the metastasis of circulating Lewis lung carcinoma cells to the lungs by attenuating mesenchymal-epithelial transition (MET). Furthermore, cell scratch assays and Matrigel invasion assays revealed that overexpression of Krüppel-like factor 4 inhibited the migration and invasion of non-small cell lung cancer cell lines A549, H1299, H226, and H1650 cells. Moreover, overexpression of Krüppel-like factor 4 attenuated TGF-b1-induced epithelial-mesenchymal transition (EMT) in A549, and inhibited the phosphorylation of c-JunNH2-terminal kinase (JNK), an important pathway in metastasis in non-small cell lung cancer. Our in vivo and in vitro findings illustrate that Krüppel-like factor 4 inhibited metastasis and migration of non-small cell lung cancer, and indicate that Krüppel-like factor 4 could be a potential therapeutic target for the treatment of non-small cell lung cancer.