NCOA3在多发性骨髓瘤耐药性产生中的作用机制及其特异性抑制剂SI-2的应用研究

The chemotherapy induced multidrug resistance is one of the most important reason for the failure of Multiple Myeloma therapy in clinic, and two dilemmas are encountered when solve this intractability: the one is the limitation in understanding the underlying molecular mechanisms, and another is the lack of specific targets and inhibitors. The nuclear receptor coactivator 3 (NCOA3) is an oncogene which plays multi-roles in many kinds of tumors, but its roles in hematological malignances were not investigated. Our preliminary data showed that the expression level of NCOA3 was significantly higher in the refractory MM patients than that in the new diagnosed patients, and patients with higher NCOA3 level had a poorer overall outcomes. In vitro studies found that there was a negative correlation between the NCOA3 expression level and the sensitivity to Bortezomib (BTZ) treatment in the immortalized MM cells, and that NCOA3 protein level in the BTZ-resistant MM cells, which were induced by increasing dosage of BTZ (starting at 0.5nM and up to 5nM during a 6 months period), was obviously upregulated that that in the parental cells; proteomics analysis and RNA-sequencing data both revealed that the protein level and mRNA level of NCOA3 were elevated significantly; using a novel NCOA3 specific inhibitor developed by Dr. Bert O’Malley lab from the Baylor College of Medicine, we found that the sensitivity to BTZ treatment was obviously increased and a synergetic effect was elicited, as well as the reversion of the drug resistance; when comparing the components of the NCOA3 complex in the wild type parental MM cells and the BTZ-resistant cells using co-immunoprecipitation assay, we found that some novel molecules were recruited into the NCOA3 complex in the BTZ-resistant MM cells. These results suggested that the NCOA3 is an important molecule in the initiation of BTZ-induced drug resistance in MM cells, and changes in expression levels and components of the NCOA3 complex will result in functional alternations in modification of the chromatin histones or transcriptional factors, which in turn regulates drug resistant genes as a consequence. In the current study, we will investigate the mechanisms of NCOA3 and the complex in the initiation of BTZ-induced drug resistance using in vitro experiments, as well as the efficacy of targeting NCOA3 in the NCOA3-/- mice as well as the SCID-hu MM model. The purpose of our study is to understand the underlying mechanisms governing BTZ-induced drug resistance in MM cells and will benefit the therapeutic pursuits for other NCOA3-associated cancers.

克服多发性骨髓瘤（MM）耐药性的产生和复发尚存在（1）耐药性产生的机制不明和（2）缺乏特异性靶点及抑制剂两大难题。核受体共激活因子3（NCOA3）是一种重要染色体修饰因子，我们前期结果发现复发MM患者中表达水平显著增高，且与恶性程度正相关；MM细胞中NCOA3表达量与对硼替佐米（BTZ）的敏感性成反比；蛋白质组学筛查发现NCOA3蛋白水平在BTZ诱导的耐药型MM细胞中显著增高；NCOA3新型抑制剂SI-2能显著提高MM对BTZ的敏感性；Co-IP发现耐药型MM细胞中NCOA3复合体可招募新的成员。本项课题将从临床标本、细胞和动物水平深入探究NCOA3在复合体在BTZ诱导MM耐药性产生中对染色体高级构象或转录复合体蛋白的修饰机制，并利用NCOA3-/-鼠和SCID移植瘤及骨破坏模型验证靶向效果。本项目将揭示NCOA3对MM耐药性产生的一种新机制并评估其在临床诊疗中的意义。

化疗耐药性的发展是多发性骨髓瘤（MM）临床治疗失败的主要原因，但遗传和表观遗传变异相互作用导致这种化疗耐药性仍然未知。在本研究中，我们发现，在以硼替佐米（BTZ）为基础的方案治疗的MM患者中，类固醇受体辅激活因子-3（SRC-3）的高表达与复发/难治性和不良预后相关。此外，在永生化细胞系中，高SRC-3增强了对蛋白酶体抑制剂（PI）诱导的细胞凋亡的抵抗力。在t（4；14）易位患者或BTZ耐药MM细胞中过度表达的组蛋白甲基转移酶NSD2通过增强其液-液相分离以超正常修饰抗凋亡基因启动子上的组蛋白H3赖氨酸36二甲基化（H3K36me2）修饰来协调升高的SRC-3。使用新开发的抑制剂SI-2靶向SRC-3或干扰其与NSD2的相互作用，可使BTZ治疗敏化，并克服体外和体内的耐药性。总之，我们的研究结果阐明了SRC-3和NSD2在MM获得性耐药中的一种先前未被认识到的协同作用，并表明SI-2可能有效地克服MM患者的耐药性。