CircIFFO1 suppresses tumor growth and metastasis of cutaneous squamous cell carcinoma by targeting the miR-424-5p/NFIB axis

Cutaneous squamous cell carcinoma (CSCC) is a severe malignancy derived from the skin. Circular RNAs (circRNAs) play an important role in the pathological process of many malignant tumors. Moreover, circIFFO1 is reported to be down-regulated in CSCC tissues compared with non-lesional skin tissues. This study aimed to explore the specific role and potential mechanism of circIFFO1 in CSCC progression. Cell proliferation ability was analyzed by 3-(4, 5-dimethylthiazol-2-y1)-2,5-diphenyl tetrazolium bromide (MTT), 5-ethynyl-2′-deoxyuridine (EdU) incorporation, and colony-formation assays. Cell cycle progression and apoptosis were detected by flow cytometry. Cell migration and invasion were examined by transwell assays. The interaction between microRNA-424-5p (miR-424-5p) and circIFFO1 or nuclear factor I/B (NFIB) was validated by dual-luciferase reporter, RNA pull-down, and RNA immunoprecipitation (RIP) assays. Xenograft tumor assay and immunohistochemistry (IHC) assay were employed to analyze the tumorigenesis in vivo. CircIFFO1 level was down-regulated in CSCC tissues and cell lines. CircIFFO1 overexpression suppressed the proliferation, migration, invasion, and promoted apoptosis of CSCC cells. CircIFFO1 acted as a molecular sponge for miR-424-5p. The anti-tumor effects mediated by circIFFO1 overexpression in CSCC cells could be reversed by miR-424-5p overexpression. miR-424-5p interacted with the 3’ untranslated region (3’UTR) of Nuclear Factor I/B (NFIB). miR-424-5p knockdown suppressed the malignant behaviors of CSCC cells, and NFIB knockdown counteracted the anti-tumor effects of miR-424-5p absence in CSCC cells. Additionally, circIFFO1 overexpression restrained xenograft tumor growth in vivo. CircIFFO1 suppressed the malignant behaviors of CSCC by mediating the miR-424-5p/NFIB axis, which provided new insights into the pathogenesis of CSCC.