Emerging role of circular RNAs in breast cancer.

Circular RNAs (cirRNAs) are generally considered as non-coding RNAs which can act as molecular sponges for miRNAs, exert regulatory roles in transcription or splicing, and interplay with RNA binding proteins. These single-stranded transcripts can affect tumor growth, the metastatic ability of cancer cells, stemness properties, and resistance to therapeutic options. Recent investigations have shown the crucial effects of circrNAs in the evolution of breast cancer. Signature of circRNAs in breast cancer samples has been mostly assessed through microarray-based methods revealing up-regulation of some circRNAs such as circ-TFF1, circACAP2, circ-TFCP2L1, hsa_circ_0000519, circDENND4C, circPLK1 and circRNA_069718, while down-regulation of other circRNAs such as hsa_circ_0000375, circYap, hsa_circ_0025202, circTADA2A-E6, circASS1 and circRNA_BARD1 in breast cancer samples. Mechanistically, these transcripts mainly affect breast cancer tumorigenesis via serving as sponges for miRNAs. In the current manuscript, we explore the results of researches that appraised the role of circRNAs in breast cancer.