hsa-miR-631 resensitizes bortezomib-resistant multiple myeloma cell lines by inhibiting UbcH10

Although bortezomib (BTZ) remains a first-line agent for multiple myeloma (MM) therapy, the development of BTZ resistance has become an indicator of poor prognosis in MM patients. It is thus urgent to develop strategies to restore the vulnerability of MM to BTZ. This study demonstrated, for the first time, that UbcH10 is highly expressed in BTZ-resistant myeloma cell lines U-266/BTZ, NCI-H929/BTZ and RPMI-8226/BTZ, which is attributed to the inactivation of post-transcriptional control. The in-depth study revealed that during the development of BTZ resistance in these cells, the hsa-miR-631 levels were decreased, which resulted in the increased expression of the target gene UbcH10. We also found that the multiple drug-resistant protein MDR1 exhibited a positive correlation with UbcH10 due to the reduced ubiquitination of MDR1, which was caused by high UbcH10 expression. Following overexpression of miR-631, both BTZ sensitivity and BTZ-induced apoptosis were enhanced in the resistant cells. Meanwhile, resensitization by miR-631 overexpression was blocked by exogenous expression of UbcH10, which was not regulated by intracellular miR-631. In conclusion, the miR-631/UbcH10/MDR1 pathway is closely associated with the development of BTZ resistance in myeloma cells, and the overexpression of miR-631 can significantly improve BTZ sensitivity in resistant myeloma cells.