The Expression Levels of Circulating miR-129 and miR-203a in Association with Breast Cancer and Related Metastasis

Background: A significant part of deaths related to breast cancer is the result of invasion to other organs. It is essential to discover new non-invasive biomarkers to improve anticipation of recurrence risk in breast cancer patients. In this study, the plasma levels of miR-129 and miR-203a were evaluated to investigate their diagnostic potential in breast cancer and its metastasis. 
Methods: In this case-control study, conducted in Tarbiat Modares University, Tehran, Iran, in 2019, Invasive Ductal Carcinoma blood samples were divided into 3 groups based on their stages as I, II/III, IV. Each group contained 30 individuals. We also recruited 30 normal individuals as a control group. Real-Time PCR was conducted to evaluate miR-129 and miR-203a expression levels. The discriminatory ability of the evaluated plasma miRNAs was assessed by ROC (Receiver Operating Characteristic) curves in breast cancer diagnosis and its metastasis. 
Results: MiR-129 and miR-203a expression levels were significantly downregulated in breast cancer. Reducing tendency was observed in the mentioned miRNAs from less to more invasive stages. The expression level of miR-129 was decreased in metastatic than non-metastatic patients and it was significantly related to metastasis. A significant association between miR-129 expression level and lymph node status was also observed (P=0.04). Evaluation of ROC curves revealed that miR-129 and miR-203a were able to discriminate breast cancer fairly and poorly respectively. The ability of miR-129 in the diagnosis of breast cancer metastasis was poor. 
Conclusion: MiR-129 and miR-203a may both act as tumor suppressor miRNAs. Our results need further evidence in a large population to be confirmed as diagnostic markers.