MicroRNA128 Regulation of Polycomb Repressor Complexes1 and 2 in Glioblastoma

描述（由申请人提供）：恶性胶质瘤（多形性胶质母细胞瘤，GBM，胶质瘤）是最常见和最具侵袭性的原发性成人脑肿瘤。GBM患者的预后仍然很差，尽管手术，放疗和化疗。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作为多梳阻遏物复合物1（PRC1）的一部分，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（GSC）的自我更新。通过对多个基因的调节，microRNA（miRNA）协调基因表达的复杂程序，并作为细胞过程的主要调节剂。因此，基于miRNA的疗法可以影响广泛的细胞程序，导致癌细胞分化、细胞周期停滞、细胞凋亡、侵袭抑制和对放射/化疗的敏感性。我们的数据显示，miR-128靶向胶质瘤细胞和GSC中的BMI1和SUZ12。这种特定的miR在GBM中弱表达，并且miR-128直接靶向BMI1和PRC2组分SUZ12。这两个PRC的同时瞄准防止了它们的部分冗余功能。我们证明了miR-128增加了GSC的放射敏感性，并且使用胶质瘤的小鼠遗传模型，证明了miR-128在胶质瘤发生的早期事件中的丢失。因此，我们的总体假设是，GSC中这种特定miR表达的恢复将通过涉及PRC 1/2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，我们因此提出：目的1：在体外表征miR-128对扩大的GSC组中的治疗致敏和随后的细胞死亡的影响;目的2：在胶质母细胞瘤的小鼠遗传模型中确定miR-128在PRC调节中的作用;目的3：确定是否可以利用miR-128使胶质母细胞瘤对体内常规疗法敏感。所提出的实验的成功完成将为PRC在胶质瘤发生和维持中的作用的基于miR的调节提供额外的机制见解，并且为使用靶向GSC中的PRC成员的miR用于治疗胶质瘤的新型治疗策略的临床转化提供理论基础。

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.