MicroRNA128 Regulation of Polycomb Repressor Complexes1 and 2 in Glioblastoma

描述（申请人提供）：恶性胶质瘤（多形性胶质母细胞瘤、GBM、胶质瘤）是最常见、侵袭性最强的成人原发性脑肿瘤。尽管进行了手术、放疗和化疗，但GBM患者的预后仍然很差。值得注意的是，在神经干细胞维持中起作用的基因，包括BMI1和SUZ12，在GBM中高度表达。BMI1作为多梳抑制复合体1 （PRC1）的一部分，而SUZ12作为PRC2的一部分。这些复合物通过修饰染色质结构在表观遗传沉默中起关键作用。PRC1/2已被证明有助于胶质瘤细胞的致瘤性和胶质瘤“干细胞样”细胞（GSCs）的自我更新。通过对多个基因的调控，microRNAs （miRNA）协调复杂的基因表达程序，并作为细胞过程的主要调节剂。因此，基于mirna的治疗可以影响广泛的细胞程序，导致癌细胞分化，细胞周期阻滞，细胞凋亡，抑制侵袭和对放射/化疗的敏感化。我们的数据显示，miR-128在胶质瘤细胞和GSCs中靶向BMI1和SUZ12。这种特殊的miR在GBM中弱表达，miR-128直接靶向BMI1和PRC2成分SUZ12。同时针对这两种prc可防止其部分冗余功能。我们证明了miR-128增加了GSCs的放射敏感性，并且使用小鼠胶质瘤遗传模型，在胶质瘤形成的早期事件中miR-128的丢失。因此，我们的总体假设是，恢复GSCs中这种特殊miR的表达将通过涉及PRC1/2复合物成员的机制导致自我更新减少和放射敏感性增加。为了追求这一总体假设的有效性，我们提出：目的1：在体外表征miR-128对治疗致敏和随后的GSCs死亡的影响；目的2：验证miR-128在胶质母细胞瘤小鼠遗传模型中调控PRC的作用；目的3：确定miR-128是否可以在体内使胶质母细胞瘤对常规疗法敏感。该实验的成功完成将为基于miR的PRC在胶质瘤形成和维持中的作用的调节提供额外的机制见解，并为使用靶向GSCs中PRC成员的miRs治疗胶质瘤的新治疗策略的临床翻译提供理论依据。

DESCRIPTION (provided by applicant): Malignant glioma (Glioblastoma multiforme, GBM, glioma) is the most common and aggressive primary adult brain tumor. The prognosis of GBM patients remains poor, despite surgery, radiation and chemotherapy. Significantly, genes that play a role in neural stem cell maintenance, including BMI1 and SUZ12, are highly expressed in GBM. BMI1 acts as part of the polycomb repressor complex 1 (PRC1) and SUZ12 as a part of PRC2. These complexes play critical role in epigenetic silencing by modifying chromatin structure. PRC1/2 have been shown to contribute to glioma cells tumorigenicity and glioma "stem-like" cells (GSCs) self-renewal. Through their regulation of multiple genes, microRNAs (miRNA) orchestrate complex programs of gene expression and act as master regulators of cellular processes. MiRNA-based therapeutics could thus impact broad cellular programs, leading to cancer cell differentiation, cell cycle arrest, apoptosis, inhibition of invasion and sensitization to radio/chemotherapy. Our data show that miR-128 targets BMI1 and SUZ12 in glioma cells and GSCs. This particular miR is weakly expressed in GBM, and, miR-128 directly targets BMI1 and PRC2 component SUZ12. This simultaneous targeting of both PRCs prevents their partially redundant functions. We demonstrated that miR-128 increases radio-sensitivity of GSCs and, using mouse genetic model of glioma, that loss of miR-128 in early event in gliomagenesis. Therefore, our overall hypothesis is that restoration of the expression of this particular miR in GSCs will result in reduced self-renewal and increased radio- sensitivity through a mechanism that involves members of PRC1/2 complexes. To pursue the validity of this overall hypothesis, we thus propose to: Aim 1: Characterize in vitro the influence of miR-128 on therapy sensitization and subsequent cell death in extended panel of GSCs; Aim 2: Validate the role of miR-128 in regulation of PRC in mouse genetic models of glioblastoma; Aim 3: Determine if miR-128 can be exploited to sensitize glioblastoma to conventional therapies in vivo. Successful completion of the proposed experiments will provide additional mechanistic insights into miR based regulation of PRC's role in gliomagenesis and maintenance and a rationale for the clinical translation of a novel therapeutic strategy using miRs that target members of PRC in GSCs for the treatment of gliomas.