Background Circular RNAs (circRNAs) are attractive candidates to be used as biomarkers of human cancers, including lung adenocarcinoma (LUAD). Our study aimed to investigate the functions and regulatory mechanisms of hsa_circ_0129047 in the tumorigenesis of LUAD. Methods Reverse transcription‐quantitative polymerase chain reaction was performed to determine the circRNA, microRNA (miRNA), and mRNA expression levels in LUAD cell lines and tissues. Tumor xenografts were established in nude mice to evaluate whether hsa_circ_0129047 affected LUAD tumor development in vivo. Cell counting kit‐8 and transwell assays were performed to assess the mechanisms by which hsa_circ_0129047 influenced the viability and migration of LUAD cells, respectively. Apoptosis was evaluated via determination of the levels of the apoptotic markers, B‐cell lymphoma‐2, and Bcl‐2‐associated X, via Western blotting. Dual‐luciferase reporter assay, RNA immunoprecipitation assay, and Pearson's correlation analysis were performed to determine the relationships among miR‐375 and hsa_circ_0129047 and activin A receptor‐like type 1 (ACVRL1). Results Downregulation of hsa_circ_0129047 levels was observed in LUAD cell lines and tissues. Meanwhile, the upregulation of hsa_circ_0129047 levels repressed the proliferative, migratory, and survival capacities of LUAD cells in vitro. Hsa_circ_0129047 exerted antitumor effects during in vivo tumor development. Finally, we demonstrated that hsa_circ_0129047 sponged miR‐375. This interaction facilitated the expression of the downstream target of miR‐375, ACVRL1, whose upregulation inhibited the development and malignancy of LUAD. Conclusion These findings demonstrate that hsa_circ_0129047 functions as a tumor inhibitor in LUAD by modulating the miR‐375/ACVRL1 axis. Hence, hsa_circ_0129047 may be a promising biomarker and gene target for LUAD treatment.

Compelling evidence has demonstrated the critical role of circular RNAs (circRNAs) during lung adenocarcinoma (LUAD) progression. Herein, we explored a novel circRNA, circ_0129047, and detailed its mechanism of action. The expression of circ 0129047, microRNA-665 (miR-665), and protein tyrosine phosphatase receptor type B (PTPRB) in LUAD tissues and cells was determined using reverse transcription quantitative polymerase chain reaction and Western blotting. Cell Counting Kit-8 and colony formation assays were conducted to detect LUAD cell proliferation, and western blotting was performed to quantify apoptosis-related proteins (Bcl-2 and Bax). Luciferase reporter and RNA immunoprecipitation assays were used to validate the predicted interaction between miR-665 and circ_0129047 or PTPRB. A xenograft assay was used for the in vivo experiments. Circ_0129047 and PTPRB were downregulated in LUAD tissues and cells, whereas miR-665 expression was upregulated. Overexpression of circ_0129047 suppresses LUAD growth in vivo and in vitro . Circ_0129047 is the target of miR-665, and the miR-665 mimic ablated the anti-proliferative and pro-apoptotic phenotypes of LUAD cells by circ_0129047 augmentation. MiR-665 targets the 3ʹUTR of PTPRB and downregulates PTPRB expression. PTPRB overexpression offsets the pro-proliferative potential of miR-665 in LUAD cells. Circ_0129047 sequestered miR-665 and upregulated PTPRB expression, thereby reducing LUAD progression, suggesting a promising approach for preventing LUAD.