Circular RNA-regulated autophagy is involved in cancer progression

Circular RNAs (circRNAs) are a sort of long, non-coding RNA molecules with a covalently closed continuous ring structure without 5'-3' polarity and poly-A tail. The modulative role of circRNAs in malignant diseases has been elucidated by many studies in recent years via bioinformatics and high-throughput sequencing technologies. Generally, circRNA affects the proliferative, invasive, and migrative capacity of malignant cells via various mechanisms, exhibiting great potential as novel biomarkers in the diagnoses or treatments of malignancies. Meanwhile, autophagy preserves cellular homeostasis, serving as a vital molecular process in tumor progression. Mounting studies have demonstrated that autophagy can not only contribute to cancer cell survival but can also induce autophagic cell death in specific conditions. A growing number of research studies have indicated that there existed abundant associations between circRNAs and autophagy. Herein, we systemically reviewed and discussed recent studies on this topic in different malignancies and concluded that the circRNA–autophagy axis played crucial roles in the proliferation, metastasis, invasion, and drug or radiation resistance of different tumor cells.