ISG20L2 suppresses bortezomib antimyeloma activity by attenuating bortezomib binding to PSMB5
Yan Yang, Yuhan Gao, Jingcao Huang, Zhuang Yang, Hongmei Luo, Fangfang Wang, Juan Xu, Yushan Cui, Hong Ding, Zhimei Lin, Xinyu Zhai, Ying Qu, Li Zhang, Ting Liu, Lingqun Ye, Ting Niu, Yuhuan Zheng
Yan Yang, Yuhan Gao, Jingcao Huang, Zhuang Yang, Hongmei Luo, Fangfang Wang, Juan Xu, Yushan Cui, Hong Ding, Zhimei Lin, Xinyu Zhai, Ying Qu, Li Zhang, Ting Liu, Lingqun Ye, Ting Niu, Yuhuan Zheng
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Research Article Hematology

ISG20L2 suppresses bortezomib antimyeloma activity by attenuating bortezomib binding to PSMB5

Abstract

The proteasome inhibitors (PIs) bortezomib and carfilzomib, which target proteasome 20S subunit beta 5 (PSMB5) in cells, are widely used in multiple myeloma (MM) treatment. In this study, we demonstrated the role of interferon-stimulated 20 kDa exonuclease-like 2 (ISG20L2) in MM PI resistance. Gain- and loss-of-function studies showed that ISG20L2 suppressed MM cell sensitivity to PIs in vitro and in vivo. Patients with ISG20L2lo MM had a better response to PIs and a longer overall survival than patients with ISG20L2hi MM. Biotinylated bortezomib pull-down assays showed that ISG20L2 competed with PSMB5 in binding to bortezomib. The surface plasmon resonance assay confirmed the direct binding of bortezomib to ISG20L2. In ISG20L2hi MM cells, ISG20L2 attenuated the binding of bortezomib to PSMB5, resulting in lower inhibition of proteasome activity and therefore less bortezomib-induced cell death. Overall, we identified a potentially novel mechanism by which ISG20L2 conferred bortezomib resistance on MM. The expression of ISG20L2 correlated with MM PI responses and patient treatment outcomes.

Authors

Yan Yang, Yuhan Gao, Jingcao Huang, Zhuang Yang, Hongmei Luo, Fangfang Wang, Juan Xu, Yushan Cui, Hong Ding, Zhimei Lin, Xinyu Zhai, Ying Qu, Li Zhang, Ting Liu, Lingqun Ye, Ting Niu, Yuhuan Zheng

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Figure 2

ISG20L2 regulates MM cell sensitivity to PIs.

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ISG20L2 regulates MM cell sensitivity to PIs. (A) CTR-KD and ISG-KD (sh1...
(A) CTR-KD and ISG-KD (sh1 used) ARD cells were treated with different drugs for 24 hours. BTZ (5 nM), CFZ (3.5 nM), doxorubicin (DOX, 2 μM), melphalan (MEL, 15 μM), and dexamethasone (DEX, 40 μM) were used. Cell apoptosis was analyzed by flow cytometry with annexin V and propidium iodide (PI) double staining (left), and the percentage of apoptotic cells was quantified (right, n = 3). Student’s t test was performed. **P ≤ 0.01; ***P ≤ 0.001. (B) AMO1 cells infected with control virus (CTR) or ISG-OE were treated with BTZ (5 nM) and CFZ (3.5 nM) for 24 hours. Cell apoptosis was analyzed (left), and the results were quantified (right, n = 3). Student’s t test was performed. **P ≤ 0.01. (C) CTR-KD versus ISG-KD ARD cells and CTR versus ISG-OE AMO1 cells were treated with BTZ (5 nM for 12 hours). Western blot results of cleaved caspase-3 and GAPDH are shown. (D) CTR-KD or ISG-KD (sh1 used) ARD cells expressing luciferase were intravenously injected into B-NDG mice to establish a human MM xenograft mouse model. Bioluminescence imaging indicated a correlation between ISG20L2 expression and MM sensitivity to BTZ in vivo (n = 5 for each group). (E) Monoclonal protein (human κ light chain secreted by ARD cells) levels in mouse peripheral blood were examined by ELISA. Two-way ANOVA with Tukey’s post hoc test was performed. (****P < 0.0001 for BTZ-treated CTR-KD vs. ISG-KD mice.) (F) Survival curves of B-NDG mice with different treatments. The Mantel-Cox test was performed. (**P < 0.01 for CTR-KD vs. ISG-KD mice treated with BTZ.)