Circular RNAs (circRNAs) are connected at the 3′ and 5′ ends by exon or intron cyclization, forming a complete ring structure. circRNA is more stable and conservative than linear RNA and abounds in various organisms. In recent years, increasing numbers of reports have found that circRNA plays a major role in the biological functions of a network of competing endogenous RNA (ceRNA). circRNAs can compete together with microRNAs (miRNAs) to influence the stability of target RNAs or their translation, thus, regulating gene expression at the transcriptional level. circRNAs are involved in biological processes such as tumor cell proliferation, apoptosis, invasion, and migration as ceRNAs. circRNAs, therefore, represent promising candidates for clinical diagnosis and treatment. Here, we review the progress in studying the role of circRNAs as ceRNAs in tumors and highlight the participation of circRNAs in signal transduction pathways to regulate cellular functions.

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Circular RNAs function as ceRNAs to regulate and control human cancer progression.

Circular RNA and its mechanisms in disease: From the bench to the clinic.

Circular RNAs (circRNAs) are a class of single-stranded, covalently closed RNA molecules with a variety of biological functions. Studies have shown that circRNAs are involved in a variety of biological processes and play an important role in the development of various complex diseases, so the identification of circRNA-disease associations would contribute to the diagnosis and treatment of diseases. In this review, we summarize the discovery, classifications and functions of circRNAs and introduce four important diseases associated with circRNAs. Then, we list some significant and publicly accessible databases containing comprehensive annotation resources of circRNAs and experimentally validated circRNA-disease associations. Next, we introduce some state-of-the-art computational models for predicting novel circRNA-disease associations and divide them into two categories, namely network algorithm-based and machine learning-based models. Subsequently, several evaluation methods of prediction performance of these computational models are summarized. Finally, we analyze the advantages and disadvantages of different types of computational models and provide some suggestions to promote the development of circRNA-disease association identification from the perspective of the construction of new computational models and the accumulation of circRNA-related data.

MicroRNAs and complex diseases: from experimental results to computational models.

Circular RNAs (circRNAs) are a class of single-stranded closed RNA molecules that are formed by precursor mRNA back-splicing or skipping events of thousands of genes in eukaryotes as covalently closed continuous loops. High-throughput sequencing and bioinformatics approaches have uncovered the broad expression of circRNAs across species. Their high stability, abundance, and evolutionary conservation among species points to their distinct properties and diverse cellular functions as efficient microRNAs and protein sponges; they also play important roles in modulating transcription and splicing. Additionally, most circRNAs are aberrantly expressed in pathological conditions and in a tissue-specific manner such as development and progression of cancer. Herein, we highlight the characteristics, functions, and mechanisms of action of circRNAs in cancer; we also provide an overview of recent progress in the circRNA field and future application of circRNAs as cancer biomarkers and novel therapeutic targets.

Circular RNAs in Cancer

CircRNAs and cancer: Biomarkers and master regulators.

Circular RNAs (circRNAs) are a type of noncoding RNAs generated from back-splicing, which have been verified to mediate multiple tumorigenesis. With the development of high-throughput sequencing, massive circRNAs are discovered in tumorous tissue. However, the potential physiological effect of circRNAs in breast cancer is still unknown. The purpose of this study is to investigate the expression profile of circRNA in breast cancer tissue and explore the in-depth regulatory mechanism in breast cancer tumorigenesis. In the present study, we screened the circRNA expression profiles in breast cancer tissue using circRNA microarray analysis. Totally 1705 circRNAs were identified to be significantly aberrant. Among these dysregulated circRNAs, hsa_circ_0001982 was markedly overexpressed in breast cancer tissue and cell lines. Bioinformatics analysis predicted that miR-143 acted as target of hsa_circ_0001982, which was confirmed by Dual-luciferase reporter assay. Loss-of-function and rescue experiments revealed that hsa_circ_0001982 knockdown suppressed breast cancer cell proliferation and invasion and induced apoptosis by targeting miR-143. In summary, our study preliminarily investigates the circRNA expression in breast cancer tissue and explores the role of competing endogenous RNA (ceRNA) mechanism in the progression, providing a novel insight for breast cancer tumorigenesis.

Circular RNA hsa_circ_0001982 Promotes Breast Cancer Cell Carcinogenesis Through Decreasing miR-143.

Neoadjuvant chemotherapy (NAC) is increasingly widely used in breast cancer treatment, and accurate evaluation of its response provides essential information for treatment and prognosis. Thus, the imaging tools used to quantify the disease response are critical in evaluating and managing patients treated with NAC. We discussed the recent progress, advantages, and disadvantages of common imaging methods in assessing the efficacy of NAC for breast cancer.

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Jia-Jun Duan

Papers

Circular RNA hsa_circ_0001982 Promotes Breast Cancer Cell Carcinogenesis Through Decreasing miR-143.

Advances in Imaging in Evaluating the Efficacy of Neoadjuvant Chemotherapy for Breast Cancer