Circ-N4BP2L2 enhances mitochondrial function in non-small cell lung cancer cells through regulating the miR-135a-5p/ARL5B axis.

Non-small cell lung cancer (NSCLC) is the main histological subtype of lung cancer with a high incidence and mortality. Circular RNAs (circRNAs) exert vital functions in various cancers by acting as a sponge of miRNAs to abolish their inhibitory effect on target genes. This study aims to explore the biological function of circRNA NEDD4 binding protein 2 like 2 (circ-N4BP2L2) in NSCLC. We found that circ-N4BP2L2 was upregulated in NSCLC tissues and cells by using RT-qPCR. A549 cells were transfected with pcDNA-circN4BP2L2 or sh-circN4BP2L2 to obtain circN4BP2L2-overexpressed or -silenced cells, and then cell proliferation, invasion and apoptosis were determined. The results showed that knockdown of circ-N4BP2L2 repressed cell proliferation, invasion as well as mitochondrial function, and promoted cell apoptosis; while overexpression of circ-N4BP2L2 resulted in the opposite results. Mechanistically, the targeting correlations between miR-135a-5p and circ-N4BP2L2 or ADP-ribosylation factorlike 5B (ARL5B) were confirmed by using dual luciferase reporter, RNA pull-down and RNA immunoprecipitation assays. In addition, we found that circ-N4BP2L2 could promote the expression of ARL5B by serving as a sponge of miR-135a-5p. Moreover, rescue assays revealed that silencing miR-135a-5p or overexpressing ARL5B was able to abate the effects of circ-N4BP2L2 knockdown on malignant phenotypes and mitochondrial function of A549 cells. Finally, tumorigenicity assay demonstrated that circ-N4BP2L2 facilitated NSCLC tumor growth in vivo. Taken together, circ-N4BP2L2 enhanced NSCLC progression via the miR-135a-5p/ARL5B axis, which may provide a novel therapeutic target of NSCLC.