RESUMO
Background: Circular ribonucleic acids (circRNAs) play a key role in the development of different types of cancer. Ferroptosis is a type of programmed cell death that contributes to cancer progression. However, the role of circRNAs in lung adenocarcinoma (LUAD) ferroptosis remains unclear. Methods: The gene expression levels of circRNA P4HB (circP4HB), microRNA-1184 (miR-1184) and Solute carrier family 7 member 11 (Slc7a11), also known as Xct were detected using quantitative real-time polymerase chain reaction (qRT-PCR). Ferroptosis of established LUAD cells was induced by erastin. Cell viability was examined via Cell Counting Kit 8 assays. Ferroptosis was evaluated by malondialdehyde (MDA), Prostaglandin-endoperoxide Synthase 2 (Ptgs2), lipid reactive oxygen species (lipid ROS), and JC-1 detection. The mechanism of circP4HB/miR-1184/SLC7A11 was investigated by luciferase reporter assays, RNA immunoprecipitation, RNA pull-down, and western blot assays. A functional for circP4HB in vivo was determined using xenograft nude mice models. Results: CircP4HB expression levels were increased in LUAD. It triggered glutathione (GSH) synthesis and, therefore protected LUAD cells from ferroptosis induced by erastin. CircP4HB may function as a competing endogenous RNA by modulating miR-1184 to regulate SLC7A11. CircP4HB inhibited ferroptosis by regulating miR-1184/ SLC7A11-mediated GSH synthesis. In vivo, overexpression of circP4HB promoted tumor growth and inhibited ferroptosis. Conclusions: The circRNA, circP4HB acts as a novel ferroptosis suppressor in LUAD. Furthermore, circP4HB protects LUAD from ferroptosis via modulation of the miR-1184/SLC7A11 axis. Our findings identified circP4HB as a novel biomarker in LUAD and warrants further investigation in the early diagnosis and treatment of LUAD.
RESUMO
Lung adenocarcinoma accounts for half of all lung cancer cases in most countries. Mounting evidence has demonstrated that microRNAs play important roles in cancer progression, and some of them can be identified as potential biomarkers. This study aimed to explore the role of miR-550a-5p, a lung adenocarcinoma-associated mature microRNA screened out from the TCGA database via R-studio and Perl, with abundant expression in samples and with 5-year survival prognosis difference, as well as having not been studied in lung cancer yet. Potential target genes were predicted by the online database. Gene ontology enrichment, pathway enrichment, protein-protein interaction network, and hub genes-microRNA network were constructed by FunRich, STRING database, and Cytoscape. Then, LIMD1, a known tumor suppressor gene reported by multiple articles, was found to have a negative correlation with miR-550a-5p. The expression of miR-550a-5p was up-regulated in tumor samples and tumor-associated cell lines. Its high expression was also correlated with tumor size. Cell line A549 treated with miR-550a-5p overexpression promoted tumor proliferation, while H1299 treated with miR-550a-5p knockdown showed the opposite result. Mechanically, miR-550a-5p negatively regulated LIMD1 by directly binding to its 3'-UTR validated by dual luciferase assay. In summary, a new potential prognostic and therapeutic biomarker, miR-550a-5p, has been identified by bioinformatics analysis and experimental validation in vitro and in vivo, which promotes lung adenocarcinoma by silencing a known suppressor oncogene LIMD1.