Smoking activates EMT in COPD bronchial epithelial cells through PIK3CA overexpression

Background

Airway remodeling caused by smoking is an important pathological change in chronic obstructive pulmonary disease (COPD), and epithelial-mesenchymal transition (EMT) is one of the core mechanisms involved in airway remodeling. However, the exact molecules and pathway mechanisms involved in the induction of EMT in COPD remain largely unknown. Numerous previous studies have elucidated that overexpression of PIK3CA promotes the proliferation and metastasis in various types of tumors by inducing EMT, while inhibition of PIK3CA can inhibit the invasion and proliferation of tumors. However, the relationship between PIK3CA and EMT has not been reported in COPD.

Methods

Fresh pulmonary specimens were collected away from the tumor site from the smoker with COPD (n = 9) and non-smokers without COPD control group (n = 9) who underwent lung tissue resection, and conducted deep sequencing of lung tissue mRNA. It was found that the PIK3CA and EMT pathways play a significant role in the development of COPD using bioinformatics. Therefore a mouse model of emphysema exposed to cigarette smoke(CS) was constructed which demonstrated increased PIK3CA expression and EMT activation in bronchial epithelial cells with increased apoptosis by immunohistochemical and immunofluorescence. In vitro, it was further confirmed the expression of PIK3CA and the activation of EMT by cigarette smoke extract (CSE)-incubated BEAS-2B cells. By PIK3CA knockout, it was proved that PIK3CA plays an important role in the EMT process.

Results

Through the analysis of mRNA sequencing data of fresh pulmonary specimens from smokers with COPD and non-smokers without COPD, we found that EMT plays a core role in COPD. Through analysis of GSEA and PPI, we found that PIK3CA is a key gene in COPD. By studying the established mouse model of COPD and BEAS-2B cells incubated with CSE, we found that CS exposure increased PIK3CA expression and associated EMT activation. CSE can induce EMT in vitro by increasing PIK3CA expression, and knockout PIK3CA can reverse CSE-induced EMT.

Conclusion

Cigarette smoke induces EMT in bronchial epithelial cells by up-regulating PIK3CA expression. PIK3CA knockdown reversed CSE-induced EMT. EMT and PIK3CA may be potential new targets for the treatment of COPD in the future.