SIRT1去乙酰化修饰GLI2对非经典Hedgehog信号通路和多发性骨髓瘤耐药性调控机制的研究

Hh信号通路在多发性骨髓瘤的耐药性中发挥重要作用，其关键转录因子GLI2转录后蛋白水平的修饰是Hh通路活化的关键。最新报道GLI2可以被乙酰化修饰，但是具体的位点、对其DNA结合能力的影响、以及对下游靶基因的调控机制尚不明确。我们发现去乙酰化酶SIRT1在骨髓瘤患者中高表达并且与其恶性程度有相关性；SIRT1通过与GLI2形成复合体阻止蛋白降解并活化Hh通路；骨髓间基质细胞与MM细胞共培养能显著上调SIRT1的表达量。本课题中，我们通过分子、细胞和动物水平的实验验证，结合临床病人标本，进一步深入探讨骨髓微环境上调SIRT1的机制，SIRT1对GLI2蛋白的化学修饰和转录能力的调控，以及促进MM产生耐药性的分子机制。该研究有助于重新认识MM耐药性产生的原因，寻找特异性药物靶点，并指导临床上开发新的治疗方案。

The Hedgehog signaling plays a very important role in Multiple Myeloma drug resistance, and the post-transcriptional modification of the key transcriptional factor GLI2 is essential for the Hedgehog signaling activation. Recent studies have revealed that GLI2 can be modified by acetylation but the acetylated amino acid sites are still unclear. Moreover, the DNA binding activity of GLI2 after acetylation modification and the details of mechanisms controlling the GLI2 processing as well as the Hh signaling downstream targets also remain obscure. Our preliminary data showed that the protein deacetylase, SIRT1, was highly expressed in MM patients and the SIRT1 expression correlated with advanced MM malignancy; overexpression of SIRT1 stabilized GLI2 protein and activated the hedgehog signaling in consequence; Co-Immunoprecipitation experiment showed that SIRT1 and GLI2 formatted a complex; co-culture with bone marrow stromal cells enhanced the expression of SIRT1 in MM cells. These results indicate that interaction of MM cells with the bone marrow stromal cells may promote the expression of SIRT1, and the latter interacts directly or recruits other molecules to modulate the GLI2 protein in purpose of activating the hedgehog signaling and ultimately results in MM cell drug resistance. In the current study, we will collect clinical MM samples, use in vitro molecular biochemistry experiments and in vivo SCID-hu mice model to mimic the bone marrow microenvironment, and explore the modification mechanisms of SIRT1 on GLI2, as well as the molecular mechanism of MM drug resistance. Our study has important significance in gaining new insights into the reason of MM drug resistance, identifying special targets, and developing new strategy for MM treatment in clinic.