Summary
Multiple myeloma (MM) is characterised by the proliferation and accumulation of malignant plasma cells in the bone marrow. Despite the progress in treatment over the last few years, MM remains incurable and the majority of patients relapse. MM stem‐like cells (MMSCs) have been considered as the main reason for drug resistance and eventual relapse. Currently, therapeutic agents are not enough to eradicate MMSCs, and finding effective strategies to eradicate MMSCs may improve the outcome of patients. Here we showed that lycorine, a natural compound from the Amaryllidaceae species, effectively inhibits the proliferation of myeloma cells from cell lines or patients, mainly through decreasing ALDH1+ cells. Mechanistically, lycorine decreases the MMSC population through inhibition of the Wnt/β‐catenin pathway by reducing the β‐catenin protein level. Moreover, lycorine could overcome the increasing proportion of ALDH1+ cells caused by bortezomib (BTZ) treatment, and a combination BTZ and lycorine have a synergistic effect on anti‐myeloma cells. Furthermore, we found a similar reduction of MMSC characteristics by lycorine in BTZ‐resistant MM cells and primary CD138+ plasma cells. Collectively, our findings indicate lycorine as a promising agent to target MMSCs to overcome the drug resistance of BTZ, and that, alone or in combination with BTZ, lycorine is a potential therapeutic strategy for MM treatments.
Multiple myeloma stem-like cells (MMSCs) are responsible for initiation and relapse, though novel treatment paradigms that effectively eradicate MMSCs are yet to be developed. Selective inhibition of the cell cycle regulatory kinase Wee1 by MK1775 is being explored as a potential anti-cancer therapeutic. We report that higher expression of Wee1 is correlated with poor survival in multiple myeloma (MM). The MM models and patientderived CD138 + plasma cells are particularly sensitive to the growth-inhibitory effects of the Wee1 inhibitor MK1775. MK1775 induces Mus81-Eme1 endonuclease-mediated DNA damage in S-phase cell cycle that results in a blockade of replication and then apoptosis. Furthermore, MK1775 strongly suppresses the features of stemness in vitro, in vivo and in primary CD138 + cells by decreasing ALDH1 + cell fraction and the expression of ALDH1. In addition, co-treatment of MK1775 with bortezomib is synergistic in vitro and in vivo. Bortezomib, although it enhances ALDH1 + cells, when combined with MK1775 abrogates this stimulatory effect on stemness. Considering MM as an invariably incurable malignancy due to the presence of heterogenic myeloma stem-like cells, our study presents inhibition of Wee1 as a promising targeted therapy for MM and provides a compelling rationale to further investigate the activity of MK1775 against myeloma in clinical settings.
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