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)是最常见和最具侵袭性的成人原发脑肿瘤。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发挥作用的基因，包括BMI1和SUZ12，在GBM中高度表达。BMI1作为多梳抑制物复合体1(PRC1)的一部分，SUZ12作为PRC2的一部分。这些复合体通过改变染色质结构，在表观遗传沉默中发挥关键作用。已有研究表明，PRC1/2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器。因此，基于miRNA的治疗方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、抑制侵袭和对放射/化疗增敏。我们的数据显示，miR-128针对胶质瘤细胞和GSC中的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。这两个PRC的同时目标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，并且利用小鼠胶质瘤的遗传模型，miR-128的丢失在胶质瘤形成的早期事件中发生。因此，我们的总体假设是，在GSC中恢复这种特定miR的表达将通过一种涉及PRC1/2复合体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，我们因此建议：目标1：在体外表征miR-128对GSC扩展小组的治疗增敏和随后的细胞死亡的影响；目标2：在小鼠胶质母细胞瘤遗传模型中验证miR-128在调节PRC中的作用；目标3：确定是否可以利用miR-128在体内使胶质母细胞瘤对传统疗法增敏。拟议实验的成功完成将为基于miR调控PRC在胶质瘤发生和维持中的作用提供更多的机械学见解，并为临床翻译一种新的治疗策略提供理论基础，该策略以GSCs中针对PRC成员的miR为靶点。

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.