Screening for drugs that restore let-7 microRNA expression in cancer

描述（由申请人提供）：本提案旨在确定新发现的Lin28致癌途径的化学抑制剂，并确定这些化合物作为潜在化疗药物的功效。let-7 microRNAs （miRNAs）通过抑制几种癌基因的表达而发挥抑癌作用：let-7在许多肿瘤类型中下调，低let-7与预后不良相关，恢复let-7表达可有效抑制模型系统中的肿瘤生长。最近发现，rna结合蛋白Lin28A和Lin28B选择性地抑制let-7的表达，从而为开发新的化疗策略来恢复癌细胞中let-7的表达提供了令人兴奋的机会。Lin28A/B通常仅在早期胚胎发育中表达，但在约15%的人类癌症中异常重新激活，并相应降低let-7水平，异位表达Lin28A/B可增强细胞增殖并促进细胞转化。重要的是，当将let-7重新引入转化细胞时，这种效应可以被消除。相反，人类癌细胞系中Lin28A或Lin28B的缺失导致细胞增殖、迁移和致瘤性降低。引人注目的是，Lin28A和Lin28B在低分化和预后最差的肿瘤亚群中被特异性激活。Lin28A招募zchc11，一种新的3'端尿苷基转移酶（TUTase）来阻止let-7的生物发生。因此，Lin28A-TUTase是癌症治疗的重要新靶点。新的高通量筛选（HTS）方法将被开发并用于鉴定在表达lin28a的癌症中恢复let-7表达的药物。HTS将采用两种互补的检测方法：一种基于细胞的系统来监测let-7的表达，一种生化检测来识别TUTase的抑制剂。Hit化合物将通过一系列的二次筛选进行验证，这些化合物对癌细胞增殖的影响将被检查。这种方法将把基础科学发现转化为开发新的有效的癌症治疗方法。

DESCRIPTION (provided by applicant): This proposal aims to identify chemical inhibitors of the newly discovered Lin28 oncogenic pathway, and to establish the efficacy of these compounds as potential chemotherapeutics. let-7 microRNAs (miRNAs) function as tumor suppressors by inhibiting the expression of several oncogenes: let-7 is downregulated in numerous tumor types, low let-7 correlates with poor prognosis, and restoration let-7 expression effectively inhibits cancer growth in model systems. It was recently found that the RNA-binding proteins Lin28A and Lin28B selectively inhibit expression of let-7 and thus provides an exciting opportunity for the development of novel chemotherapeutic strategies to restore let-7 expression in cancer. Lin28A/B are normally only expressed during early embryonic development but is aberrantly reactivated in ~15% of human cancers, with a corresponding reduction in let-7 levels, and ectopic Lin28A/B expression enhances cell proliferation and promotes cellular transformation. Importantly, this effect can be abrogated when let-7 is reintroduced into the transformed cells. Conversely, depletion of Lin28A or Lin28B in human cancer cells lines results in decreased cell proliferation, migration, and tumorigenicity. Strikingly, Lin28A and Lin28B are specifically activated in the subset of tumors that are poorly differentiated and carry the worst prognosis. Lin28A recruits Zcchc11, a novel 3' terminal uridylyl transferase (TUTase) to block let-7 biogenesis. Thus Lin28A-TUTase represents an important new target for cancer treatment. Novel high-throughput screening (HTS) approaches will be developed and utilized to identify drugs that restore let-7 expression in Lin28A-expressing cancers. Two complementary assays will be utilized for HTS: a cell-based system to monitor let-7 expression, and a biochemical assay to identify inhibitors of the TUTase. Hit compounds will be validated using a series of secondary screens and the effect of these compounds on cancer cell proliferation will be examined. This methodology will translate basic science discoveries to the development of new and effective cancer treatments.