Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 15 2 2024 02 28 81 93 Mahdieh Salimi Department of Medical Genetics, Institute of Medical Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran Shamim Dashti Gohari Department of Medical Genetics, Institute of Medical Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran 2023 10 30 2023 12 24 Breast cancer is the most common malignancy among women, and early diagnosis and targeted therapy have garnered significant attention. Non-coding RNAs have emerged as potential diagnostic, prognostic, and treatment biomarkers for breast cancer. This study aimed to evaluate the expression of non-coding RNAs, specifically miR-506 and circular RNA 000284, and their target gene SNAIL-2 in breast tumors compared to normal controls. The study also focused on clinicopathological characteristics, and plasma was monitored for expression of circ0000284 to identify a possible accessible cancer-related marker. Using the SYBR-Green Real-time PCR technique, total RNA was extracted from 80 breast tumors and normal adjacent tissues, and circ0000284, miR-506, and SNAIL2 expression were analyzed. The results showed overexpression, down-regulation, and up-regulation of circRNA 000284, miR-506, and SNAIL-2 gene, respectively. These expression changes were associated with advanced stages of the disease and lymph nodal involvement, which are signs of a poor prognosis. Additionally, a positive direct correlation was observed between circRNA000284 expression in tumors and plasma. Moreover, it was discovered that circ-0000284 sponged miR-506, causing up-regulation of SNAIL-2 as its mRNA target. The upregulation of SNAIL-2 as an epithelial-mesenchymal-transition (EMT)factor leads to poor prognosis in breast cancer and is epigenetically regulated by miR-506 and circRNA 000284. Therefore, the overexpression of circRNA000284 in plasma could be considered an indicator of lymph nodal involvement and advanced stages of cancer, and nominated as a poor prognostic biomarker for future considerations. https://bccr.tums.ac.ir/index.php/bccrj/article/view/498