PIR and breast cancer: Additionally, earlier studies showed that piR-34736, piR-35407, piR-36249, piR-34377, and piR-36318 are typically downregulated, while piR-651, piR-36026, piR-20582, piR-932, piR-36743, piR-021285, and piR-31106 are upregulated in breast cancer [302].