† These authors contributed equally.
Objectives: Piwi-interacting RNAs (piRNAs), are a family of small, non-coding RNA transcipts, previously thought to silence gene expression in germ cells through the piRNA-PIWI complex. In recent studies, piRNAs were found to be prominently involved in the development and prognosis of malignant tumors. The study aims to identify differentially expressed circulating piRNAs in breast cancer patients. Methods: 8 piRNAs were tested using Real-time PCR assay in the plasma samples of 33 healthy subjects and 37 breast cancer patients. Results: In this study, we found that piR-651, piR-17458, and piR-20485 were significantly down-regulated in breast cancer patients when compared with healthy controls. Further, piR-20485 was found to be decreased in patients with metastatic disease relative to those with carcinoma in situ. Conclusion: These findings demonstrate that piRNAs are potential biomarkers in peripheral blood for breast cancer diagnosis.