ABSTRACT
BACKGROUND: Epithelial-mesenchymal transition (EMT), a phenotypic conversion of the epithelial to mesenchymal state, contributes to cancer progression. Currently, several microRNAs (miRNAs) are associated with EMT-mediated cancer progression, but the contribution of miR-34a to EMT in cancer cells remains controversial. The present study aimed to clarify the role of miR-34a in the EMT-related phenotypes of human non-small cell lung cancer (NSCLC) cell lines, A549 (p53 wild-type) and H1299 (p53-deficient). METHODS: The miR-34a mimic and p53 small interfering RNA (siRNA) were transfected into the cells using Lipofectamine, and the obtained total RNA and cell lysates were used for real-time polymerase chain reaction and Western blotting analysis, respectively. RESULTS: The introduction of the miR-34a mimic led to an increase in the mRNA and protein expression levels of α-smooth muscle actin (α-SMA), a mesenchymal marker gene, in A549, but not in H1299 cells. Additionally, miR-34a-induced the upregulation of p53 activity and migration was observed in A549, but not in H1299 cells. However, under the p53-knockdown condition, only α-SMA upregulation by miR-34a was abolished. CONCLUSION: These findings indicate a close relationship between p53 and miR-34a-induced EMT in p53-wild type NSCLC cells, which provides novel insights about the role of miR-34a in EMT-like phenotypic changes in NSCLC.
Subject(s)
Carcinoma, Non-Small-Cell Lung/genetics , Lung Neoplasms/genetics , MicroRNAs/genetics , Tumor Suppressor Protein p53/genetics , A549 Cells , Actins/metabolism , Carcinoma, Non-Small-Cell Lung/metabolism , Cell Line, Tumor , Epithelial-Mesenchymal Transition , Gene Expression Profiling , Gene Expression Regulation, Neoplastic , Humans , Lung Neoplasms/metabolism , Up-RegulationABSTRACT
Several studies using bleomycin (BLM)-induced lung injury rat model revealed that epithelial-mesenchymal transition (EMT) contributes to pulmonary fibrosis. Conversely, microRNAs (miRNAs) are considered as useful markers of various diseases. In the present study, we aimed to characterize the EMT state through focusing on alveolar epithelial cells and identify the miRNAs that can be used as markers to predict pulmonary fibrosis using a BLM-induced lung injury rat model. Intratracheal administration of BLM increased hydroxyproline, a component of collagen, in lung tissues at day 14, but not at day 7. However, BLM induced EMT at day 7, which was accompanied with increased mRNA expression of α-smooth muscle actin, a representative EMT marker, in alveolar epithelium, thereby suggesting that EMT occurs prior to pulmonary fibrosis in alveolar epithelial cells. Using this rat model, the expression levels of several EMT-associated miRNAs were examined, and miR-222 was found to be upregulated in alveolar epithelial cells as well as bronchoalveolar lavage fluid from day 3. Our findings indicate that EMT in alveolar epithelial cells may occur before pulmonary fibrosis, and miR-222 may be used as a potential marker for early prediction of pulmonary fibrosis.
Subject(s)
Bleomycin/toxicity , Epithelial-Mesenchymal Transition/drug effects , Lung Injury/chemically induced , Pulmonary Fibrosis/chemically induced , Alveolar Epithelial Cells/cytology , Alveolar Epithelial Cells/drug effects , Animals , Antibiotics, Antineoplastic/administration & dosage , Antibiotics, Antineoplastic/toxicity , Bleomycin/administration & dosage , Lung Injury/genetics , Lung Injury/physiopathology , Male , MicroRNAs/genetics , Pulmonary Fibrosis/genetics , Pulmonary Fibrosis/physiopathology , Rats , Rats, Sprague-Dawley , Time FactorsABSTRACT
PURPOSE: Several anticancer drugs including bleomycin (BLM) and methotrexate (MTX) cause serious lung diseases such as pulmonary fibrosis. Although evidences showing the association of epithelial-mesenchymal transition (EMT) with pulmonary fibrosis are increasing, the mechanism underlying anticancer drug-induced EMT has been poorly understood. On the other hand, miR-34a, a non-coding small RNA, has been highlighted as a key factor to regulate EMT in lung. In this study, we elucidated the role of miR-34a in anticancer drug-induced EMT using A549/ABCA3 cells as a novel type II alveolar epithelium model. METHODS: Expression levels of α-smooth muscle actin (α-SMA) mRNA, miR-34a, and p53 were evaluated by real-time PCR and western blot analysis, respectively. RESULTS: BLM and MTX induced EMT-like morphological changes and increase in mRNA expression level of α-SMA, an EMT marker. Also, both drugs increased the expression level of miR-34a. Furthermore, mRNA expression level of α-SMA was enhanced by introduction of miR-34a mimic into A549/ABCA3 cells. To examine the mechanism underlying drug-induced enhancement of miR-34a expression, we focused on p53/miR-34a axis. Both drugs upregulated protein expression of p53, an inducer of miR-34a, as well as phosphorylation of Ser15 in p53. CONCLUSIONS: These findings indicated that p53/miR-34a axis may contribute to anticancer drug-induced EMT in type II alveolar epithelial cells.
