Milad Asadi
1 
, Sanam Sadeghi-Mohammadi
2, Najibeh Shekari
3, Venus Zafari
1, Zahra Soleimani
4, Ufuk Mert
5, Maryam Seyyedi
6, Ayse Caner
1,7* , Habib Zarredar
6* 1 Department of Basic Oncology, Institute of Health Sciences, Ege University, Izmir, Turkey
2 ATMP Department, Breast Cancer Research Center, Motamed Cancer Institute, ACECR, Tehran, Iran
3 Department of Immunology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
4 Rahat Breath and Sleep Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
5 Atatürk Health Care Vocational School, Ege University, Izmir, Turkey
6 Tuberculosis and Lung Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
7 Department of Parasitology, Faculty of Medicine, Ege University, Izmir, Turkey
Abstract
Circular RNAs (circRNAs) are a novel class of non-coding RNAs primarily generated through a back-splicing processes. These molecules exhibit extensive expression across various tissues, indicating their significant role in numerous biological processes, particularly in complex diseases such as cancer. Based on their origin, structure, and biogenesis, circular RNAs are categorized into exonic circRNAs (ecirc-RNAs), circular intronic RNAs (ci-RNAs), or exonic-intronic circRNAs (EIci-RNAs). Due to their covalently closed-loop configuration, it is necessary to develop specialized techniques to study them. CircRNAs are known to function as protein and microRNA sponges, regulate transcription, interact with RNA-binding proteins (RBPs), and, in rare cases, serve as templates for translation. In this review, we provide an overview of circRNA features, biogenesis, and functions. In addition, we summarize molecular methods for studying them and explain their significant roles in malignancies.