Circular RNAs (circRNAs), a class of covalently closed RNAs formed by a back-splicing reaction, have been involved in the regulation of diverse oncogenic processes. In this article we describe circVAMP3, a novel circular RNA overexpressed in RH4, a representative cell line of alveolar rhabdomyosarcoma. We demonstrated that circVAMP3 has a differential m⁶A pattern opposed to its linear counterpart, suggesting that the two isoforms can be differently regulated by such RNA modification. Moreover, we show how circVAMP3 depletion in alveolar rhabdomyosarcoma cells can impair cell cycle progression, through the alteration of the AKT-related pathways, pointing to this non-coding RNA as a novel regulator of the alveolar rhabdomyosarcoma progression and as a putative future therapeutic target.

Circular RNAs (circRNAs), covalently closed RNAs that originate from back-splicing events, participate in the control of several processes, including those that occur in the development of pathological conditions such as cancer. Hereby, we describe circAFF1, a circular RNA overexpressed in alveolar rhabdomyosarcoma. Using RH4 and RH30 cell lines, a classical cell line models for alveolar rhabdomyosarcoma, we demonstrated that circAFF1 is a cytoplasmatic circRNA and its depletion impacts cell homeostasis favouring cell migration through the downregulation of genes involved in cell adhesion pathways. The presented data underline the importance of this circular RNA as a new partial suppressor of the alveolar rhabdomyosarcoma tumour progression and as a putative future therapeutic target.

Circular RNAs (circRNAs) are a class of RNA with multiple functions, including the ability to be translated. Several intrinsic features of circRNAs, such as high stability, confer them advantages over linear RNAs; therefore, circRNA-based drugs have recently received increasing attention. However, the inefficiency of their cap-independent translation and the difficulties in the large-scale production of long circRNAs negatively impact on their use in therapy. Some efforts have been done to solve these issues related to circRNA adoption, but, to date, circRNA translation still relies on long IRESs (600-800) and chemical group addition. In this study, identified a 63-nt element able to drive circRNA translation comparably to the most commonly used IRESs. This element includes a a 13-nt sequence previously reported to enhance linear RNA translation and a segment of the UTR of the endogenously translated circRNA circZNF609. Notably, this element combines a comparable IRES-like efficiency to a considerably shorter length, expanding the landscape of ORFs potentially suitable for being translated from circRNAs and enhancing their potential as therapeutic agents in therapy.