Circular RNAs have been identified as diagnostic and therapeutic targets for various
tumors. The expression of circ_rac
GTPase-activating protein 1 (circRACGAP1) is reported to drive the development of
non-small cell lung cancer (NSCLC). This study further explored the potential mechanism of circRACGAP1-mediated development of NSCLC. The circRACGAP1 level was detected by quantitative RT-PCR. Sphere formation, CD133-positive cell percentage, and expression of octamer-binding
transcription factor 4, Sox2, Nanog, and CD133 were detected to evaluate stemness of NSCLC. Migration and invasion were determined using wound healing and transwell assays.
Protein expression was measured using Western blotting. The molecular mechanism was evaluated using
RNA pull-down,
RNA immunoprecipitation, and coimmunoprecipitation assays. In vivo
tumor growth and
metastasis were determined in nude mice. circRACGAP1 was highly expressed in NSCLC and was associated with stemness marker Sox2 expression. The stemness,
metastasis, and epithelial mesenchymal transformation were repressed in circRACGAP1-depleted NSCLC cells. Mechanistically, circRACGAP1 recruited
RNA-binding protein polypyrimidine tract-binding protein 1 to enhance the stability and expression of sirtuin-3 (
SIRT3), which subsequently led to replication timing regulatory factor 1 (RIF1) deacetylation and activation of the Wnt/β-
catenin pathway. circRACGAP1 overexpression counteracted
SIRT3 or RIF1 knockdown-mediated inhibition in stemness and
metastasis of NSCLC cells. The in vivo
tumor growth and
metastasis were repressed by circRACGAP1 depletion. Patients with NSCLC with a higher serum exosomal circRACGAP1 level had a lower overall survival rate. In conclusion, circRACGAP1 facilitated stemness and
metastasis of NSCLC cells through the recruitment of
polypyrimidine tract-binding protein 1 to promote SIRT3-mediated RIF1 deacetylation. Our results uncover a novel regulatory mechanism of circRACGAP1 in NSCLC and identify circRACGAP1 as a promising therapeutic target.