RUNX2 regulates cell proliferation, autophagy activity and apoptosis in LUAD cell via transcriptionally activating TMEM74.

Abstract

Lung cancer has the highest mortality rate of all cancers, and lung adenocarcinoma (LUAD) is one of the most common subtypes. TMEM74 expression is upregulated in both lung cancer patients and LUAD cell lines, and its high expression correlates with poor patient survival. Targeted TMEM74 knockdown and overexpression vectors were successfully constructed, and stably transfected LUAD cell lines were established. TMEM74 was found to significantly enhance LUAD cell proliferation and colony formation while suppressing apoptosis. TMEM74 overexpression elevated the LC3II/I ratio, reduced p62 levels, and boosted autolysosome formation, whereas TMEM74 knockdown exerted opposite effects. Bafilomycin A1-mediated autophagy inhibition abrogated the pro-proliferative and anti-apoptotic effects driven by TMEM74 overexpression. Subcutaneous xenograft experiments revealed that TMEM74 knockdown restrained tumor growth, and impaired autophagic activity in tumor. A positive correlation was observed between the expression levels of Runt-related transcription factor 2 (RUNX2) and TMEM74 in LUAD. RUNX2 overexpression in LUAD cells induced upregulation of TMEM74 mRNA levels. Dual luciferase reporter assays demonstrated that RUNX2 significantly enhanced the transcriptional activity of TMEM74 in LUAD cells. TMEM74 knockdown reversed the increased cell proliferation, reduced apoptosis and enhanced autophagosome formation induced by RUNX2 overexpression in LUAD cells. Collectively, our experimental results demonstrate that RUNX2 transcriptionally activates TMEM74, thereby promoting LUAD cell proliferation and autophagy and inhibiting cell apoptosis in vitro; TMEM74 knockdown suppresses tumor growth in vivo.