METTL16 enhances proteasome inhibitor resistance in multiple myeloma by inhibiting eIF2α-PERK interaction and promoting PSMB5 translation.

Targeting IGF1R/Insr Pathway with Approved ALK-Inhibitors Overcomes Proteasome Inhibitor Resistance in Multiple Myeloma

Profiling the Cell Surface Landscape of Proteasome Inhibitor-Treated and -Resistant Multiple Myeloma to Guide Immunotherapy Targeting, Diagnosis, and Biology

Novel therapies for multiple myeloma.

SAKK 65/08: A Phase I Dose Escalation Study of Bortezomib in Combination with Nelfinavir in Patients with Advanced Hematologic Malignancies

Exosome-Transmitted PSMA3 and PSMA3-AS1 Promotes Proteasome Inhibitors Resistance in Multiple Myeloma

Introduction In the past decade, response and survival rates in multiple myeloma (MM) patients have been greatly increased by newer therapies. Nevertheless, most patients with MM eventually die from relapsed/refractory disease. Previous studies in our lab and in others have shown that exportin 1 inhibitors (XPO1i) are potent anti-MM drugs, whether used as single agents or in combination with proteasome inhibitors (PIs), immunomodulator drugs (IMiDs), anthracyclines, or alkylating agents. Ixazomib (IXA), an orally available PI, has been shown to be effective when combined with IMiDs, dexamethasone, alkylating agents, and/or prednisone for the treatment of patients with MM. We investigated whether the clinical XPO1i selinexor (SEL) or eltanexor (ELT) combined with IXA could overcome PI resistance in MM cell lines and in ex vivo bone marrow aspirates from PI-refractory patients. Materials and Methods PI-resistant MM cell lines 8226B25 and U226PSR and their respective parental cell lines, 8226 and U266, were treated in vitro and in vivo (mice) with SEL/IXA or ELT/IXA combinations or with each drug as a single agent. Bone marrow aspirates from newly diagnosed and PI-refractory MM patients were treated ex vivo with SEL/IXA or ELT/IXA and assayed for apoptosis. Mechanistic studies included NFkB and IkBα protein assays, immunofluorescence microscopy, ImageStream flow-cytometry, and proximity-ligation assay. IkBα knockdown and NFkB transcriptional activity were measured in SEL/IXA- or ELT/IXA-treated MM cells. Results SEL and ELT each sensitized parental and, to a lesser extent, PI-resistant MM cells to IXA, as measured by apoptosis. XPO1i/IXA treatments inhibited U266 and 8226 MM tumor growth and increased survival in mice; however, PI-resistant tumors were not sensitized by XPO1i/IXA treatment. Myeloma cells isolated from both newly diagnosed and PI-refractory MM patients were sensitized by XPO1i to IXA, as compared to untreated and single agent-treated MM cells, without affecting non-MM cells. Immunofluorescence microscopy, Western blot, and ImageStream analyses of MM cells showed increased nuclear IkBα with the XPO1i/PI treatments. Proximity ligation found increased IkBα-NFkB complexes in treated MM cells. IkBα knockdown abrogated XPO1i/PI-induced cytotoxicity in MM cells. XPO1i/PI treatment decreased NFkB transcriptional activity. Conclusions In previous studies, we found that SEL sensitized PI-resistant cell lines to carfilzomib and bortezomib; however, IXA was less effective in these same MM cells. SEL or ELT used in combination with IXA have the potential to overcome PI drug resistance in MM patients. Sensitization may be due to inactivation of the NFkB pathway by IkBα. Further investigation is underway to examine these mechanisms. The results presented in this study support combinatorial clinical trials in relapsed and refractory MM patients who use PI therapies. Citation Format: Joel G. Turner, Jana Dawson, Alexis Bauer, Juan Gomez, Erkan Baloglu, Yosef Landesman, Daniel M. Sullivan. Ixazomib combined with the nuclear export inhibitors selinexor or eltanexor for the treatment of multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 285.

DDX3X Promotes Multiple Myeloma Cell Survival and Proteasome Inhibitor Resistance through Modulation of Stress Granule Assembly and MAPKAPK2 Translation

Proteasome inhibitor (PI) resistance remains a major therapeutic obstacle in the treatment of multiple myeloma (MM). MM cells demonstrate pronounced dependence on insulin and insulin-like growth factor-1 signaling via their cognate receptors, IGF-1R and INSR. In this study, we identify ceritinib, a clinically approved inhibitor of anaplastic lymphoma kinase (ALK), as a drug, which can inhibit IGF-1R/INSR activity and downstream PI3K/AKT/mTORC1 signaling. Ceritinib can overcome PI-resistance in MM when used in combination with carfilzomib. This synergy was consistently observed across in vitro and in vivo models, and primary patient-derived MM cells. Mechanistically, MM cells exploit IGF- 1R/INSR signaling to sustain expression of key molecular chaperones, including HSP70 and BiP, which are critical for maintaining proteostasis under conditions of high protein synthesis and turnover. Pharmacological inhibition of IGF-1R/INSR signaling by ceritinib abrogates this adaptive stress response, thereby preventing the upregulation of cytoprotective heat shock proteins upon proteasome inhibition. This disruption results in enhanced accumulation of protein aggregates, increased protein polyubiquitination, endoplasmic reticulum stress, and activation of apoptotic pathways. Collectively, our findings support the repurposing of ceritinib in combination with carfilzomib as a translationally relevant and safe strategy to circumvent PI resistance in MM, warranting further clinical investigation in the relapsed/refractory disease setting.

Targeting Redox Overcomes Proteasome Inhibitor Resistance in Multiple Myeloma

The Contribution of Proteasome Subunits to Myeloma Cell Viability and Proteasome Inhibitor Sensitivity

Anti-Myeloma Activity of a Syringolin Analog: A Dual 20S Proteasome Inhibitor of Beta 2 and 5 Subunits

Skp2 Inhibition Diminishes Essential Cell Survival Markers c-Maf and c-Myc, Enhancing Therapeutic Efficacy Against Drug Resistant Multiple Myeloma

Focusing PI and IMiD Resistance in Multiple Myeloma: Impact of DNA Methylation

RFWD2 Induces Cellular Proliferation and Proteasome Inhibitor Resistance By Mediating p27 Ubiqutinaiton in Multiple Myeloma

Introduction: Multiple myeloma (MM) is a plasma malignancy characterized by an accumulation of misfolded immunoglobulins in the cell. Although proteasome inhibitor (PI) can treat MM by inhibiting ubiquitin-proteasome system (UPS), autophagy as a compensatory protein clearance mechanism, it still leads to drug resistance. The discovery of new targets that can simultaneously inhibit UPS and autophagy will provide great potential for the treatment of MM. Methods: The proliferation, invasion, migration, proteasome activity and autophagy were detected in CRIP1- knockdown /overexpression and control MM cells. Co-IP (Co-Immunoprecipitation) with TAP/MS (Tandem affinity purification/Mass spectrum) was performed to detect the binding of USP7, CRIP1 and PA200. Myeloma xenograft model was used to determine the role of CRIP1 to promote proliferation of MM cells and induce BTZ resistance in vivo. Results: The levels of CRIP1 were significantly increased in plasma cells from NDMM (newly diagnosed multiple myeloma) compared to healthy donors, and further increased in patients with RRMM (relapsed/refractory multiple myeloma). Moreover, the high expression of CRIP1 is significantly related to the poor prognosis of MM patients, especially those treated with BTZ. Our results in vitro and in vivo showed that CRIP1 knockdown noteworthy inhibited the cell growth, invasion, migration. MM cells were more sensitive to PIs-induced cell growth arrest when CRIP1 knockdown. The proteasome activity and the protein level of LC3B-Ⅱ of the MM cells were significantly reduced with CRIP1 knockdown. Co-IP analysis showed that CRIP1 formed a complex with USP7/PA200. The protein level of CRIP1 decreased and the ubiquitination CRIP1 increased with USP7 inhibition. These data suggested that CRIP1 is the substrate of USP7.CRIP1 promotes the de-ubiquitination and stabilization of PA200 mediated by USP7 by interacting with USP7 and PA200, which in turn promotes MM cell survival and drug resistant. Functional inhibition of CRIP1 by knocking down of USP7 or PSME4 in CRIP1 OE MM cell line led to a decrease of the activity of proteasome and autophagy, thus enhancing the sensitivity to PIs in intro and in vivo. Conclusion: CRIP1 plays a critical role in MM progression and PIs resistance by formation of CRIP1/USP7/PA200 complex. High level of CRIP1 is a biomarker for high-risk MM patients. CRIP1 is a potential target for MM therapy, can simultaneously inhibit proteasome activity and autophagy. Encore Abstract - previously submitted to EHA 2023 The research was funded by the following foundations:(a) CAMS Innovation Fund for Medical Sciences (CIFMS) (2021-I2M-1-040 and 2022-I2M-1-022), (b) National NaturalScience Foundation of China (82170194, 81920108006, 82270175) and Natural Science Foundation of Fujian Province of China (2021J02040). Keywords: Diagnostic and Prognostic Biomarkers, Multiple Myeloma, Tumor Biology and Heterogeneity No conflicts of interests pertinent to the abstract.