circHMGCS1 Promotes the Progression of NSCLC by Regulating the HuR/SFPQ/TNF Pathway

Among lung cancers, non-small-cell lung cancer (NSCLC) is the most common type. Evidence demonstrates that abnormal expression of circular RNAs (circRNAs) is associated with cancer progression through interactions with RNA-binding proteins (RBPs). Therefore, further elucidation of the role of circular RNAs may provide new therapeutic targets for NSCLC patients. This study identified a novel circRNA, circHMGCS1 (hsa_circ_0072387), using circRNA microarrays. Validation and characterization of circHMGCS1 were performed by Sanger sequencing and RNase R treatment. CCK-8 and Transwell assays were used to determine the function of circHMGCS1 in cell proliferation and migration. The interaction between circHMGCS1 and human antigen R (HuR) protein was verified by RNA pull-down and RNA immunoprecipitation (RIP) assays. The effect of HuR on the stability of splicing factor proline- and glutamine-rich (SFPQ) mRNA was verified by dual-luciferase reporter gene assay and actinomycin D treatment. We found that circHMGCS1 was upregulated in NSCLC cells and tissues. Mechanistically, circHMGCS1 binds to HuR, and its high expression stabilizes HuR by inhibiting its ubiquitin-mediated degradation. HuR was shown to mediate the stability of SFPQ mRNA and promote the progression of NSCLC. RNA sequencing analysis indicated that SFPQ may inhibit apoptosis by suppressing tumor necrosis factor (TNF) signaling. This study revealed that circHMGCS1 contributes to NSCLC progression by stabilizing oncogenic HuR and promoting post-transcriptional upregulation of SFPQ, highlighting its potential as a diagnostic and prognostic biomarker for NSCLC.