KLF9-dependent pathways in multiple myeloma drug resistance

 描述（由申请人提供）：多发性骨髓瘤（MM）是一种浆细胞疾病，约占所有血液恶性肿瘤的10%。可逆性蛋白酶体抑制剂硼替佐米（BTZ）联合其他药物是MM治疗的主要策略。2012年批准的不可逆蛋白酶体抑制剂卡非佐米（CFZ）在复发性/难治性MM肿瘤中显示出有希望的结果，并且比BTZ更有效地诱导MM细胞死亡。虽然MM患者的总体生存率大幅增加，但该疾病仍然无法治愈。BTZ和CFZ在MM细胞中的细胞毒性机制远未被理解。该提案的最终目标是表征这些机制，并确定MM干预的新靶点。 最近，我们已经证明，BTZ诱导MM细胞死亡的部分通过表观遗传上调的Kruppel样转录因子9（KLF 9）的水平。此外，在BTZ治疗前从患者分离的MM细胞中KLF 9 mRNA水平（通过微阵列评估）与BTZ治疗的良好反应相关。CFZ的细胞毒性高于BTZ。我们通过头对头比较表明，CFZ比BTZ更有效地上调KLF 9水平。因此，我们将检验以下假设：KLF 9的上调是BTZ和CFZ细胞毒性的共同机制，并且CFZ的更高细胞毒性是由于KLF 9的更有效诱导。 BTZ和CFZ细胞毒性的KLF 9依赖性途径尚不清楚。为了寻找这些途径，我们利用ChIP-Seq和定量RT-PCR分析，发现KLF 9抑制直接或间接降低氧化应激的基因表达。在参与氧化应激反应的KLF 9靶点中，我们确定了两个基因，它们表现出KLF 9、CFZ和BTZ依赖性表达模式，其遗传或药理学抑制部分重现了BTZ或CFZ在这些细胞中诱导的效应。因此，我们将在MM小鼠模型中检验以下假设：KLF 9靶点的部分消耗介导BTZ和CFZ的细胞毒性，而这些靶点的更有效的遗传或药理学抑制降低肿瘤负荷并增加BTZ或CFZ的疗效。

 DESCRIPTION (provided by applicant): Multiple myeloma (MM) is a plasma cell disorder that accounts for approximately 10% of all hematologic malignancies. Reversible proteasome inhibitor bortezomib (BTZ) in combination with other agents represents a major strategy for MM treatment. Approved in 2012, irreversible proteasome inhibitor carfilzomib (CFZ) demonstrated promising results in relapsed/refractory MM tumors and more potently induced death in MM cells than BTZ. Although the overall survival of MM patients has substantially increased, the disease remains incurable. The mechanisms of BTZ and CFZ cytotoxicity in MM cells are far from being understood. The ultimate goal of this proposal is to characterize such mechanisms and to identify novel targets for MM intervention. Recently, we have demonstrated that BTZ induces death in MM cells in part via epigenetic upregulation of the levels of Kruppel-like transcription factor 9 (KLF9). Moreover, KLF9 mRNA levels in MM cells isolated from patients prior to BTZ therapy (as assessed by microarrays) correlated with good response to BTZ treatment. CFZ demonstrated higher cytotoxicity than BTZ. We showed via head-to-head comparison that CFZ upregulates KLF9 levels even more efficiently than BTZ. Thus we will test the hypothesis that upregulation of KLF9 is a common mechanism of cytotoxicity of BTZ and CFZ, and that the higher cytotoxicity of CFZ is due to a more efficient induction of KLF9. KLF9-dependent pathways underlying cytotoxicity of BTZ and CFZ are unknown. In search for such pathways, we utilized ChIP-Seq and quantitative RT-PCR assays and discovered that KLF9 suppresses expression of genes that directly or indirectly decrease oxidative stress. Among KLF9 targets involved in response to oxidative stress, we identified two genes that demonstrated KLF9-, CFZ- and BTZ-dependent expression pattern and whose genetic or pharmacological inhibition partially recapitulates the effects induced in these cells by BTZ or CFZ. Thus, we will test the hypothesis that partial depletion of KLF9 targets mediates cytotoxicity of BTZ and CFZ, while more efficient genetic or pharmacological inhibition of these targets reduces tumor burden and increases efficacy of BTZ or CFZ in a mouse model of MM.