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

描述（由申请人提供）：本提案旨在鉴定新发现的Lin 28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疗效。let-7 microRNA（miRNA）通过抑制几种癌基因的表达而起到肿瘤抑制剂的作用：let-7在许多肿瘤类型中下调，低let-7与不良预后相关，并且let-7表达的恢复有效地抑制模型系统中的癌症生长。最近发现RNA结合蛋白Lin 28 A和Lin 28 B选择性抑制let-7的表达，从而为开发新的化疗策略以恢复癌症中的let-7表达提供了令人兴奋的机会。Lin 28 A/B通常仅在早期胚胎发育期间表达，但在~15%的人类癌症中异常地再活化，let-7水平相应降低，并且异位Lin 28 A/B表达增强细胞增殖并促进细胞转化。重要的是，当let-7被重新引入转化细胞中时，这种作用可以被消除。相反，人类癌细胞系中Lin 28 A或Lin 28 B的耗尽导致细胞增殖、迁移和致瘤性降低。令人惊讶的是，Lin 28 A和Lin 28 B在低分化和预后最差的肿瘤亚组中特异性活化。Lin 28 A募集Zcchc 11，一种新的3'末端尿苷酰转移酶（TUTase）来阻断let-7生物合成。因此，Lin 28 A-TUTase代表了癌症治疗的重要新靶标。新的高通量筛选（HTS）方法将被开发和利用，以确定药物，恢复让-7表达的Lin 28 A表达的癌症。HTS将采用两种互补试验：一种基于细胞的系统，用于监测let-7表达;另一种生化试验，用于鉴定TUTase抑制剂。命中化合物将使用一系列二次筛选进行验证，并将检查这些化合物对癌细胞增殖的影响。这种方法将把基础科学发现转化为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.