Department of Physiology and Pathophysiology, School of Basic Medical Science, Tianjin Medical University, Heping, Tianjin, 300070, China.
School of Medicine, Hunan Normal University, Changsha, Hunan, 410006, China.
Oncogene. 2020 Jan;39(4):922-934. doi: 10.1038/s41388-019-1037-6. Epub 2019 Oct 1.
Multiple myeloma (MM) is still incurable despite the successful application of proteasome inhibitors in clinic. Bortezomib represents the most common chemotherapy for MM, whereas acquired drug resistance and eventually developed relapse remain the major obstruction. In the current study, we established bortezomib-resistant myeloma cell lines and screened gene expression profiles using single cell RNA-sequencing. Resistant MM cells exhibited increased clonogenic potential, specific metabolic, and epigenetic signatures, along with the self-renewal signaling characteristic of MM stem-like cells. Aberrant activation of hedgehog (Hh) signaling was correlated with drug resistance and stem cell-like transcriptional program. The key transcriptional factor GLI2 of the Hh pathway was restricted in the high acetylation and low ubiquitination states in bortezomib-resistant myeloma cells. Further investigation revealed that SIRT1 deacetylates and stabilizes GLI2 protein at lysine 757 and consequentially activates the Hh signaling, and itself serves as a direct target of Hh signaling to format a positive regulating loop. Using combination screening with an epigenetic compound library, we identified the SIRT1 specific inhibitor S1541 and S2804 had very obvious synergetic antimyeloma effect. Sirt1 inhibition could partially impeded the Hh pathway and conferred bortezomib sensitivity in vitro and in vivo. Notably, elevated SIRT1 level was also a prominent hallmark for the resistant myeloma cells, and this expression pattern was confirmed in myeloma patients, but independent of RAS/RAF mutations. Clinically, SIRT1 expression in patients with complete response was suppressed but elevated in relapsed patients, and retrospective analysis showed patients with higher SIRT1 expression had poorer outcomes. In conclusion, the cooperation of SIRT1 and Hh is an important mechanism of drug resistance in myeloma, and therapeutics combining SIRT1 inhibitors will sensitize myeloma cells to proteasome inhibitors.
多发性骨髓瘤（MM）尽管在临床中成功应用了蛋白酶体抑制剂，但仍无法治愈。硼替佐米是 MM 最常用的化疗药物，而获得性耐药最终导致复发仍然是主要障碍。在本研究中，我们建立了硼替佐米耐药骨髓瘤细胞系，并使用单细胞 RNA 测序筛选基因表达谱。耐药 MM 细胞表现出增加的集落形成能力、特定的代谢和表观遗传特征，以及 MM 干细胞样细胞的自我更新信号特征。 hedgehog（Hh）信号的异常激活与耐药和干细胞样转录程序相关。Hh 通路的关键转录因子 GLI2 在硼替佐米耐药骨髓瘤细胞中被限制在高乙酰化和低泛素化状态。进一步的研究表明，SIRT1 在赖氨酸 757 处去乙酰化并稳定 GLI2 蛋白，从而激活 Hh 信号，并且自身作为 Hh 信号的直接靶标形成正反馈调节环。通过与表观遗传化合物库的组合筛选，我们发现 SIRT1 特异性抑制剂 S1541 和 S2804 具有非常明显的协同抗骨髓瘤作用。 Sirt1 抑制可部分阻断 Hh 通路并在体外和体内赋予硼替佐米敏感性。值得注意的是，升高的 SIRT1 水平也是耐药骨髓瘤细胞的一个显著特征，并且在骨髓瘤患者中得到了证实，但与 RAS/RAF 突变无关。临床上，完全缓解患者的 SIRT1 表达受到抑制，但复发患者的表达升高，回顾性分析表明 SIRT1 表达较高的患者预后较差。总之，SIRT1 和 Hh 的合作是骨髓瘤耐药的重要机制，联合 SIRT1 抑制剂的治疗将使骨髓瘤细胞对蛋白酶体抑制剂敏感。
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