ObjectiveAccumulating studies reported the crucial roles of tRFs in tumorigenesis. However, their further mechanisms and clinical values remains unclear. This study aimed at the further investigation of tRF-Leu in breast cancer chemotherapy resistance.MethodsThe high-throughput sequencing was performed and identified the downregulation of tRF-Leu in MCF7/ADR cells. The function of tRF-Leu in breast cancer cells and breast cancer chemotherapy resistance was investigated in vitro and in vivo, including colony formation assay, CCK-8 assay, transwell assay and apoptosis assay. The binding site of tRF-Leu on BIRC5 was verified by dual-luciferase assay.ResultstRF-Leu was downregulated in MCF7/ADR cells. Overexpression of tRF-Leu inhibited the migration of breast cancer cells. Furthermore, tRF-Leu could reverse the resistance of MCF7/ADR cells to Adriamycin both in vitro and in vivo. BIRC5 was a target of tRF-Leu, which might be involved in the chemotherapy resistance regulation.ConclusionWe demonstrated that tRF-Leu could inhibit the chemotherapy resistance of breast cancer by targeting BIRC5. These findings might identify new biomarkers of breast cancer therapy and bring new strategies to reverse chemotherapy resistance.