TMEM229A suppresses non-small cell lung cancer progression via inactivating the ERK pathway

Transmembrane protein 229A (TMEM229A) is a member of the TMEM family that plays an important role in tooth differentiation and development. However, the expression level and biological role of TMEM229A in cancer remains unknown. The present study aimed to investigate the expression level of TMEM229A in non-small cell lung cancer (NSCLC), as well as its effect and mechanism on NSCLC progression. Clinical specimens from patients with NSCLC were enrolled from the First People's Hospital of Huzhou (Huzhou, China). TMEM229A expression was detected using reverse transcription-quantitative PCR (RT-qPCR), western blotting and immunohistochemical analysis. The relationship between TMEM229A expression and the survival rate of patients with NSCLC was analyzed using Kaplan-Meier Plotter datasets. The effects of TMEM229A on cell proliferation, migration and invasion were detected using Cell Counting Kit-8, colony formation, soft agar, real-time cellular analysis and Transwell assays. The expression levels of epithelial-mesenchymal transition (EMT)-related proteins, as well as ERK and AKT phosphorylation were determined via RT-qPCR and western blot analysis. The results demonstrated that TMEM229A expression was significantly downregulated in human NSCLC tissues and in several cell lines compared with adjacent normal lung tissues and BEAS-2B cells, respectively. Survival analysis of lung adenocarcinoma and squamous cell lung carcinoma cases identified that low TMEM229A expression was associated with a poor prognosis. The in vitro assays indicated that overexpressing TMEM229A significantly inhibited cell proliferation, migration and invasion, while TMEM229A knockdown had the opposite effect. Mechanistically, TMEM229A overexpression effectively increased E-cadherin expression and reduced N-cadherin, snail family transcriptional repressor 1 and MMP2 expression, indicating that EMT was suppressed. In addition, overexpression of TMEM229A reduced the expression levels of phosphorylated (p)-ERK and p-AKT, and this effect was partially suppressed by the incorporation of specific ERK inhibitor PD98059. Collectively, the results of the present study demonstrated that the effects of TMEM229A on inhibiting cell proliferation, migration and invasion were partially mediated by inactivating the ERK signaling pathway, thereby providing a potential therapeutic target for the treatment of NSCLC.