CircHERC1 promotes non-small cell lung cancer cell progression by sequestering FOXO1 in the cytoplasm and regulating the miR-142-3p-HMGB1 axis.

BACKGROUND: Noncoding RNAs such as circular RNAs (circRNAs) are abundant in the human body and influence the occurrence and development of various diseases. Non-small cell lung cancer (NSCLC) is one of the most common malignant cancers. Information on the functions and mechanism of circRNAs in lung cancer is limited; thus, the topic needs more exploration. The purpose of this study was to identify aberrantly expressed circRNAs in lung cancer, unravel their roles in NSCLC progression, and provide new targets for lung cancer diagnosis and therapy. METHODS: High-throughput sequencing was used to analyze differential circRNA expression in patients with lung cancer. qRT‒PCR was used to determine the level of circHERC1 in lung cancer tissues and plasma samples. Gain- and loss-of-function experiments were implemented to observe the impacts of circHERC1 on the growth, invasion, and metastasis of lung cancer cells in vitro and in vivo. Mechanistically, dual luciferase reporter assays, fluorescence in situ hybridization (FISH), RNA immunoprecipitation (RIP) and RNA pull-down experiments were performed to confirm the underlying mechanisms of circHERC1. Nucleocytoplasmic localization of FOXO1 was determined by nucleocytoplasmic isolation and immunofluorescence. The interaction of circHERC1 with FOXO1 was verified by RNA pull-down, RNA immunoprecipitation (RIP) and western blot assays. The proliferation and migration of circHERC1 in vivo were verified by subcutaneous and tail vein injection in nude mice. RESULTS: CircHERC1 was significantly upregulated in lung cancer tissues and cells, ectopic expression of circHERC1 strikingly facilitated the proliferation, invasion and metastasis, and inhibited the apoptosis of lung cancer cells in vitro and in vivo. However, knockdown of circHERC1 exerted the opposite effects. CircHERC1 was mainly distributed in the cytoplasm. Further mechanistic research indicated that circHERC1 acted as a competing endogenous RNA of miR-142-3p to relieve the repressive effect of miR-142-3p on its target HMGB1, activating the MAPK/ERK and NF-κB pathways and promoting cell migration and invasion. More importantly, we found that circHERC1 could bind FOXO1 and sequester it in the cytoplasm, adjusting the feedback AKT pathway. The accumulation of FOXO1 in the cytosol and nuclear exclusion promoted cell proliferation and inhibited apoptosis. CircHERC1 is a new circRNA that promotes tumor function in NSCLC and may serve as a potential prognostic biomarker and therapeutic target for NSCLC. CONCLUSIONS: CircHERC1 is a new circRNA that promotes tumor function in NSCLC and may serve as a potential diagnosis biomarker and therapeutic target for NSCLC. Our findings indicate that circHERC1 facilitates the invasion and metastasis of NSCLC cells by regulating the miR-142-3p/HMGB1 axis and activating the MAPK/ERK and NF-κB pathways. In addition, circHERC1 can promote cell proliferation and inhibit apoptosis by sequestering FOXO1 in the cytoplasm to regulate AKT activity and BIM transcription.

circTAB2 inhibits lung cancer proliferation, migration and invasion by sponging miR-3142 to upregulate GLIS2.

Circular RNAs (circRNAs) are a specialized circular structure, are deregulated in cancers and play essential roles in biological processes involved in tumor progression. However, the mechanism by which circRNAs affect lung tumorigenesis and progression remains largely unexplored. To investigate the role of circRNA in lung cancer, circRNA expression profile was screened by bioinformatics analysis. The levels of circTAB2, miR-3142, and GLIS family zinc finger 2 (GLIS2) were measured by quantitate real-time (qRT-PCR) or western blot. Cell proliferation, apoptosis, migration and invasion were detected by EdU, flow cytometry, and transwell assays, respectively. Bioinformatics, western blot, RIP, pull down, dual luciferase reporter and rescue experiments were used to verify the direct relationship between miR-3142 and circTAB2 or GLIS2. The xenograft assays were used to assess the role of circTAB2 in vivo.CircTAB2 exhibited low expression in cancer tissues. Gain and loss-of-function assays indicated that circTAB2 could inhibit cell proliferation, migration and invasion. Functional studies revealed that circTAB2 acted as a miRNA sponge, directly interacted with miR-3142 and consequently regulated GLIS2 /AKT. Taken together, circTAB2 serves as an inhibitory role in lung cancer through a novel circTAB2 /miR-3142 /GLIS2 /AKT pathway and could be exploited a novel marker in lung cancer.