Exosomes are nanoscale
phospholipid bilayer vesicles that can be artificially engineered into vectors for the treatment of
cancer.
Circular RNA (
circRNA), a type of
non-coding RNA, has crucial regulatory functions in various aspects of
cancer, such as
tumorigenesis, apoptosis, proliferation, invasion,
metastasis and chemo- and radiotherapeutic resistance, as well as in
cancer prognosis. Notably, the exosomal transfer of
circRNAs may function to both promote and inhibit
cancer. Numerous studies have addressed the importance of
circRNAs in
cancer and non-coding RNAs (such as
microRNAs and long non-coding RNAs) in exosomes. However, little research has focussed on a class of RNAs called exosomal
circRNAs. The present review discusses current studies regarding exosomal
circRNAs, including their biogenesis and biological functions, their abundance in exosomes and possible sorting mechanisms and their potential roles in both promoting and inhibiting
cancer. It is predicted that in the next five years there will be increasing research exploring the functional mechanisms of exosomal
circRNA in various diseases, in particular their roles in
cancer genesis and progression.