tRNA-derived fragment tRF-17-8SPOL52 induces resistance to bortezomib in multiple myeloma via autophagy activation.

Drug resistance limits the long-term survival of patients with multiple myeloma. The role of tRNA-derived fragments (tsRNAs) in bortezomib resistance in myeloma remains unknown. In this study, the most significantly upregulated tsRNA in relapsed/refractory myeloma was screened. RNA interference was used to explore the function of this tsRNA. The mechanism of the tsRNA-mediated resistance was explored by Ago-RIP-sequencing, dual-luciferase reporter assay, and transmission electron microscopy. tRF-17-8SPOL52 was identified as the most highly expressed tsRNA in relapsed/refractory myeloma. tRF-17-8SPOL52 promoted bortezomib resistance in vitro and in vivo. Ago-RIP-sequencing and dual-luciferase reporter assay showed that tRF-17-8SPOL52 negatively regulated RUBCN. Data from Ago-silenced myeloma cells suggested that the regulation of RUBCN by tRF-17-8SPOL52 was Ago-dependent. Further research showed increased autophagy induced by tRF-17-8SPOL52. In constructed RUBCN overexpressed or inhibited myeloma cells, tRF-17-8SPOL52 promoted cell autophagy by inhibiting RUBCN. Rescue experiments with chloroquine and rapamycin showed that tRF-17-8SPOL52 mediated bortezomib resistance by promoting autophagy. We concluded that tRF-17-8SPOL52 activates autophagy by inhibiting RUBCN in an Ago-dependent manner, which in turn leads to bortezomib resistance in myeloma.