Focus on Dicer inhibition as a novel treatment for brain tumors

 描述（由申请人提供）：我们建议的重点是评估Dicer抑制是否是选择性靶向髓母细胞瘤细胞同时保留 神经元虽然Dicer的microRNA依赖性功能是众所周知的，但最近的研究已经确定了Dicer在DNA损伤修复中的一种新的，microRNA独立的功能。由于基因组完整性的维持对于经历组成性复制应激诱导的DNA损伤的快速分裂细胞是至关重要的，我们评估了Dicer是否是在小脑发育的背景下解决体内这种DNA损伤所必需的。在缺乏Dicer的情况下，快速分裂的小脑颗粒神经元前体（CGNP）积累DNA损伤，导致其变性。值得注意的是，这种变性被p53缺陷拯救，表明Dicer缺陷触发了p53介导的DNA损伤途径的激活。与Dicer在增殖CGNP中的高表达相反，我们发现Dicer在小脑颗粒神经元中几乎检测不到。这些结果表明，与增殖的CGNP不同，Dicer可能不是有丝分裂后神经元存活所必需的-我们将在小鼠模型中测试这一假设，在该模型中，我们可以在有丝分裂后小脑神经元中有条件地选择性删除Dicer。 重要的是，我们还将评估Dicer的失活是否会引发髓母细胞瘤中的细胞死亡。髓母细胞瘤是儿童小脑肿瘤，其产生于发育期以外的CGNP的异常和持续增殖。髓母细胞瘤细胞表达Dicer，我们预测，正如在发育过程中增殖的CGNP所见，增殖的髓母细胞瘤肿瘤细胞也依赖于Dicer来解决内源性DNA损伤。我们将在两种髓母细胞瘤小鼠模型中检验这一假设，在这两种模型中，我们可以容易地评估Dicer缺失对肿瘤生长以及肿瘤消退的结果。总之，这些实验批判性地评估了Dicer作为神经母细胞瘤治疗靶点的意外潜力，神经毒性最小。

 DESCRIPTION (provided by applicant): The focus of our proposal is to evaluate whether Dicer inhibition is an effective strategy to selectively target medulloblastoma cells while sparing neurons. While the microRNA-dependent functions of Dicer are well known, recent studies have identified a novel, microRNA-independent function of Dicer in DNA damage repair. As maintenance of genomic integrity is critical for rapidly dividing cells that experience constitutiv replicative stress-induced DNA damage, we evaluated whether Dicer was essential for resolving such DNA damage in vivo in the context of developing cerebellum. In the absence of Dicer, the rapidly dividing cerebellar granule neuron precursors (CGNPs) accumulated DNA damage, which resulted in their degeneration. Remarkably, this degeneration was rescued by p53 deficiency, indicating that Dicer deficiency triggered the activation of the p53-mediated DNA damage pathway. In contrast to the high expression of Dicer in proliferating CGNPs, we found that Dicer is virtually undetectable in cerebellar granule neurons. These results suggest that unlike the proliferating CGNPs, Dicer may not be essential for survival in postmitotic neurons - a hypothesis we will test in a mouse model where we can conditionally delete Dicer selectively in the postmitotic cerebellar neurons. Importantly, we will also evaluate whether inactivation of Dicer could trigger cell death in medulloblastomas. Medulloblastomas are pediatric cerebellar tumors that arise from the aberrant and sustained proliferation of CGNPs beyond the developmental period. Medulloblastoma cells express Dicer, and we predict that, just as seen with the proliferating CGNPs during development, the proliferating medulloblastoma tumor cells also depend on Dicer for resolving endogenous DNA damage. We will test this hypothesis in two mouse models of medulloblastoma where we can readily assess the outcome of Dicer deletion on tumor growth as well as tumor regression. Together, these experiments critically evaluate the unexpected potential of Dicer as a therapeutic target for medulloblastoma with minimal neurotoxicity.