microRNA-155 and Lymphoma

弥漫性大B细胞淋巴瘤(DLBCL)是成人最常见的淋巴系统恶性肿瘤； 仅各州每年就诊断出30.000例新病例。这种肿瘤在临床和分子水平上 异质性的，只有一半的患者能存活下来。MicroRNAs(MiRNA)是非蛋白质的 编码的RNA通过与目标转录本的3‘非编码区配对来控制基因的表达。虽然miRNAs 在癌症中经常被破坏，但它们在DLBCL发病机制中的作用尚不清楚。MiRNA-155(miR- 155)在侵袭性DLBCL亚型中过表达。这种miRNA的致癌性质是 在E？miR-155转基因小鼠中得到证实，而其在淋巴细胞生物学中的关键作用表现为 有功能的动物。然而，miR-155促进淋巴肿大的机制仍然存在。 未知。使用全基因组方法和验证性策略，我们直接发现了miR-155 靶向转录因子Smad5，并显著减弱转化生长因子β/骨形态发生蛋白介导的ID2，a 致癌转录因子PAX5的关键负调控因子。此外，我们还发现DLBCL细胞 过表达miR-155或Smad5 shRNA的转基因品系对生长产生抗性 转化生长因子β1对p21基因表达的抑制作用这样做的总体目标是 建议阐明miR-155在DLBCL中的作用，并测试Smad5靶向的假设，通过 破坏转化生长因子/骨形态发生蛋白信号模块的多个下游效应器，是miR-155的核心 淋巴肿大。我们的具体目标是：1)建立miR-155、Smad5和Smad5之间的相互作用 人原代DLBCL和miR-155-/-小鼠成熟B细胞中的转化生长因子β/骨形态发生蛋白信号，2)特征 体外和体内ID2调节缺陷在miR-155介导的淋巴肿大中的作用 3)明确Smad5调节p21表达的机制，并在体内确立Smad5的作用 Pax5在与miR-155过表达和Smad5特异性敲除相关的淋巴瘤中的表达。这个 到目前为止，miR-155和转化生长因子途径之间的联系是高度相关的。这些研究 可以打造Smad5在癌症中的作用，并强调一种新的机制，癌细胞通过这种机制逃脱 肿瘤抑制转化生长因子信号。对这些下游组件的完整表征 回应应该提高我们对正常和恶性淋巴细胞生物学的理解，并发现 治疗高表达miR-155的DLBCL的新机会。

Diffuse Large B-cell Lymphoma (DLBCL) is the most common lymphoid malignancy in adults; in the United States alone 30.000 new cases are diagnosed every year. This tumor is clinically and molecularly heterogeneous and only half of the patients will survive their disease. MicroRNAs (miRNA) are non-protein coding RNAs which control gene expression by pairing to the 3'UTR of target transcripts. Although miRNAs are often disrupted in cancer, their role in the pathogenesis of DLBCL remains unclear. MiRNA-155 (miR- 155) is overexpressed in aggressive subtypes of DLBCL. The oncogenic nature of this miRNA was confirmed in E¿-miR-155 transgenic mice, whereas its key role in lymphocyte biology was shown in loss of function animals. However, the mechanisms by which miR-155 contributes to lymphomagenesis are still unknown. Using genome-wide approaches and confirmatory strategies we uncovered that miR-155 directly targets the transcription factor SMAD5 and significantly impairs the TGF¿/BMP-mediated induction of ID2, a key negative regulator of the oncogeneic transcription factor PAX5. Furthermore, we found that DLBCL cell lines genetically modified to overexpress miR-155 or a SMAD5 shRNA become resistance to the growth inhibitory effects of TGF¿1 in association with a block in p21 expression. The overall objective of this proposal is to elucidate the role of miR-155 in DLBCL and test the hypothesis that SMAD5 targeting, by disrupting multiple downstream effectors of the TGF¿/BMP signaling module, is at the core of the miR-155 lymphomagenesis. Our specific aims are: 1) Establish the interplay between miR-155, SMAD5 and TGF¿/BMP signals in primary human DLBCLs and mature B-cells from miR-155-/- mice, 2) Characterize in vitro and in vivo the contribution of a defective ID2 regulation to miR-155-mediated lymphomagenesis and, 3) Define the mechanisms by which SMAD5 regulates p21 expression, and establish in vivo the role of PAX5 in the lymphomas associated with miR-155 overexpression and SMAD5-specific knockdown. The hitherto unexplored connection between miR-155 and the TGF¿ pathway is highly relevant. These studies could forge a role for SMAD5 in cancer and highlight a novel mechanism by which cancer cells escape the tumor suppressing TGF¿ signals. Complete characterization of the downstream components of these responses should improve our understanding of normal and malignant lymphocyte biology and uncover novel opportunities for therapeutic manipulation of DLBCLs overexpressing miR-155.