MDSCs调控piRNA介导DNA甲基化参与骨髓瘤干细胞形成及耐药的分子机制

The formation and stemness maintenance of multiple myeloma cancer stem cells (MM CSCs) depend on bone marrow microenvironment. Myeloid-derived suppressor cells (MDSCs) participate in the pathogenesis of MM as one of the main components of the microenvironment, however, its effects and regulation mechanism on MM CSCs is still unclear. Our previous studies confirmed that piRNA-823 regulate the cell cycle of MM cells through DNA methylation. In the preliminary experiment we found MDSCs can significantly promote the rate of side population cells and increase piRNA-823 levels in MM. DNA methylation is an important way for epigenetic regulation of CSCs, therefore we speculate that MDSCs possibly upregulates piRNA-823 expression to induce DNA methylation, which then promotes the formation of MM CSCs and mediates chemoresistance to MM. This project aims to establish an in vitro MDSCs-MM co-culture system and in vivo SCID-rab-MM tumor bearing mice model, to observe the role of MDSCs in the MM CSCs formation and chemoresistance to MM. Furthermore, down regulate the expression of piRNA-823 or block DNA methylation levels, to investigate the mechanism and exact target by which MDSCs induce MM CSCs formation. This project is expected to clarify a new mechanism of MM occurrence and chemoresistance from the perspective of CSCs and immunology, to provide a new target for the treatment of MM.

多发性骨髓瘤干细胞（MM CSCs）的形成和“干性”维持有赖于骨髓微环境。髓源性抑制细胞（MDSCs）作为微环境重要成员参与MM发病，然而其调控MM CSCs的作用及机制尚不明确。我们前期研究证实piRNA-823通过介导DNA甲基化调控MM周期；预实验发现MDSCs可提高MM侧群细胞比例，上调piRNA-823表达。DNA甲基化是表观遗传学调控CSCs的重要方式，因此我们推测：MDSCs可能通过调控piRNA-823介导DNA甲基化，促进MM CSCs的形成和MM耐药。本项目拟建立MDSCs-MM共培养体系与SCID-rab-MM小鼠模型，观察MDSCs促MM CSCs形成及耐药的作用，进一步沉默piRNA-823表达或阻断DNA甲基化水平，探讨MDSCs诱导MM CSCs形成的分子机制和靶点。本项目有望从癌干细胞与免疫学角度，进一步阐明MM发生和耐药的新机制，为MM的治疗提供新靶点。

多发性骨髓瘤的形成和干性的维持有赖于骨髓微环境。髓源性抑制细胞（MDSCs）作为微环境重要成员参与MM发病，然而MDSCs对MM CSCs的作用及机制尚不明确。我们的前期研究证实了piRNA-823通过介导DNA甲基化调控MM周期，且预实验发现MDSCs可提高MM侧群细胞比例，上调piRNA-823表达。本项目通过建立G-MDSCs-MM共培养体系，证实G-MDSCs可促进MM细胞系中的SP细胞比例、增加肿瘤球形成、上调干性相关基因的表达。进一步的机制研究发现，这种调节作用是通过DNA甲基化通路实现。沉默piRNA-823在MM细胞系的表达，可在共培养体系中抑制G-MDSCs对MM干性的促进作用，在荷瘤小鼠体内抑制肿瘤生长和血管新生。而且我们的临床数据显示，患者骨髓的G-MDSCs比例和piRNA823水平与预后明显相关。本研究从癌干细胞与免疫学角度阐述了MM发生和干性维持的新机制，为日后MM治疗提供了新的思路和理论依据。