CiRS-7/CDR1as; An oncogenic circular RNA as a potential cancer biomarker.

Circular RNAs (circRNAs) as a new class of non-coding RNAs (ncRNAs) play role in gene regulation in multicellular organisms via various interactions with nucleic acids, proteins and particularly microRNAs. They have been found to be involved in a number of biological functions particularly in regulation of cell cycle, and extracellular interactions. Thus, dysregulation of circRNAs is found to be associated with several human diseases and especially numerous types of cancers. ciRS-7 is an example of circRNAs which have been studied in a number of human diseases like neurological diseases, diabetes mellitus, and importantly different malignancies. It has been found to regulate cell proliferation and malignant features in cancer cells. CiRS-7 is upregulated in several cancers and its overexpression promoted malignant phenotype of cancer cells via enhancing cell proliferation, migration, and invasion in vitro and in vivo. As a competing endogenous RNA (ceRNA), ciRS-7 is found to sponge miR-7 as the most common miRNA target in interaction together. Functional analyses show role of ciRS-7 in downregulation of miR-7 and involvement of a series of signaling pathways in turn through them it is believed that ciRS-7 regulates malignant behaviors of cancer cells. Clinical studies demonstrate upregulation of ciRS-7 in cancer tissues compared to their non-cancerous adjacent tissues, correlation with worse clinicopathological features in cancerous patients and an independent prognostic factor. In this review, we have an overview to the role of ciRS-7 in development and progression of cancer and also assess its potentials as a diagnostic and prognostic biomarker in human cancers.