Bladder Cancer: Role of Circular RNAs in Oncogenesis, Tumor Suppression, and Therapeutic Target Identification.

In order to identify new treatment modalities and targets for the treatment of bladder cancer (BLC), we have searched the literature (PubMed) for circular RNAs (circRNAs) that mediate efficacy in preclinical BLC-related in vivo systems. Pathogenesis-affecting circRNAs can be up-regulated or down-regulated depending on their function as oncogenes or tumor suppressors. We have grouped the identified circRNAs according to functional aspects or protein categories, such as involvement in drug resistance, transmembrane proteins, secreted proteins, mediators of signaling, enzymes with pathogenic potential, transcription factors, as well as circRNAs involved in microRNA (miR) processing and epigenetic modifications. The identified up-regulated targets can be modulated with small molecules or antibody-based drugs depending on their druggability. Down-regulated circRNAs can potentially be reconstituted by replacement therapy, whereas up-regulated circRNAs can be inhibited by nucleic acid (NA)-based inhibitors. The validity of the approach of exploring circRNAs and their corresponding targets for therapeutic intervention was underlined by the identification of circRNAs that up-regulate fibroblast growth factor receptors, which can be inhibited by erdafitinib, an approved agent for the treatment of bladder cancer.