Circular RNA circFCHO2(hsa_circ_0002490) promotes the proliferation of melanoma by directly binding to DND1.

Circular RNAs (circRNAs) have been documented to play crucial roles in the biology of various cancers. However, their investigation in melanoma is still at an early stage, particularly as a broader mechanism beyond acting as miRNA sponges needs to be explored. We report here that circFCHO2(hsa_circ_0002490), a circRNA encompassing exons 19 and 20 of the FCHO2 gene, exhibited a consistent overexpression in melanoma tissues. Furthermore, elevated circFCHO2 levels demonstrated a positive correlation with the malignant phenotype and poor prognosis among the 158 melanoma patients studied. Besides, we observed that heightened levels of circFCHO2 promoted melanoma cell proliferation, migration, and invasion in vitro, along with contributing to tumor growth in vivo. Furthermore, we found differences in the secondary structure of circFCHO2 compared to most other circular RNA structures. It has fewer miRNA binding sites, while it has more RNA binding protein binding sites. We therefore speculate that circFCHO2 may have a function of interacting with RNA binding proteins. Mechanistically, it was confirmed by fluorescence in situ hybridization (FISH), RNA-pull down, RNA immunoprecipitation (RIP), and western blotting assays that circFCHO2 interacts with dead end protein homolog 1 (DND1) and reverses the inhibition of the PI3K/AKT signaling pathway by binding to DND1. Our findings reveal that circFCHO2 drives melanoma progression by regulating the PI3K/AKT signaling pathway through direct binding to DND1 and may serve as a potential diagnostic biomarker and therapeutic target for the treatment of melanoma.