Exosomal circRNAs: key modulators in breast cancer progression

Breast cancer (BC) poses significant challenges globally, necessitating a deeper understanding of its complexities. Exosomes are cell-specific secreted extracellular vesicles of interest, characterized by a lipid bilayer structure. Exosomes can carry a variety of bioactive components, including nucleic acids, lipids, amino acids, and small molecules, to mediate intercellular signaling. CircRNAs are a novel class of single-stranded RNA molecules, characterized by a closed-loop structure. CircRNAs mainly exert ceRNA functions to intricately modulate gene expression and signaling pathways in breast cancer, influencing tumor progression and therapeutic responses. The unique packaging of circRNAs within exosomes serves as novel genetic information transmitters, facilitating communication between BC cells and microenvironmental cells, thereby regulating critical aspects of BC progression, immune evasion, and drug resistance. Besides, exosomal circRNAs possess the capabilities of serving as diagnostic and therapeutic biomarkers of BC, due to their stability, specificity, and regulatory roles in tumorigenesis and metastasis. Therefore, this review aims to elucidate the novel roles and mechanisms of exosomal circRNAs in BC progression, as well as their potential for diagnosis and therapeutics. The ongoing investigations of exosomal circRNAs will potentially revolutionize treatment paradigms and improve patient outcomes of BC.