Understanding the mechanism of action for anticancer sulfonamides that target splicing

父应用程序项目摘要/摘要 尽管最近取得了进展，但癌症仍然是美国的主要死亡原因， 迫切需要新的治疗方法。对数百种人类肿瘤的全基因组研究揭示了前mRNA 剪接作为癌细胞生长的关键途径，因此是新疗法的有吸引力的靶点。许多 参与前mRNA剪接的蛋白质缺乏酶活性，因此通常难以靶向 小分子药物。我们最近发现了一类抗癌磺胺类药物，靶向前- mRNA剪接，我们称之为SPLAM（剪接抑制剂磺酰胺）。 SPLAM通过募集RBM 39（RNA结合基序39）作为DCAF 15（DDB 1/CUL）的新底物而起作用 相关因素15）。DCAF 15是CUL 4 E3泛素连接酶受体复合物的一部分。因此，在这方面， RBM 39向DCAF 15的募集导致RBM 39泛素化和蛋白酶体降解。RBM 39是 对于选择内含子和外显子前mRNA剪接是重要的。因此，由于SPLAM 处理后，RBM 39降解导致前体mRNA剪接缺陷。特别地雷的作用机制是： 类似于FDA批准的药物，沙利度胺和来那度胺（也称为IMiD）。IMiD招募 cereblon是DCAF蛋白家族的另一个成员。IMiD与CRBN的结合具有 多效性效应，其是靶向独特的新底物或抑制内源性 cereblon的活动。 目前，尚不清楚SPLAM与DCAF 15的结合对替代的新底物具有什么影响， 内源活性在我们的第一个目标中，我们建议鉴定一种DCAF 15突变，该突变对SPLAM具有抗性， 以确定受SPLAM影响的靶细胞通路。在我们的第二个目标中，我们提出了一套 实验以鉴定DCAF 15内源性底物以及RBM 39以外的新底物。 基于SPLAM的治疗的临床开发将需要确定哪些患者最有可能 回答。我们已经发现RBM 39降解仅导致癌细胞亚群中的细胞死亡。在我们 最后的目的，我们提出了一组实验，以了解这种选择性的基础上，通过研究功能 RBM 39在SPLAM敏感和不敏感细胞中的表达。特别是，我们的初步数据表明， 在人类癌症中也发现的剪接因子突变的细胞对SPLAM敏感。我们 提出了一组实验来研究RBM 39生物学和SPLAM在人类癌症模型中的敏感性 携带这些剪接突变。

Parent Application Project Summary / Abstract In spite of recent advances, cancer remains a leading cause of death in the United States, and there is an urgent need for new therapies. Genome-wide studies of hundreds of human tumors have revealed pre-mRNA splicing as a critical pathway for cancer cell growth, and thus an attractive target for new therapies. Many of the proteins involved with pre-mRNA splicing lack enzymatic activity, and therefore are unusually difficult to target with small molecule drugs. We have recently discovered a class of anticancer sulfonamides that target pre- mRNA splicing which we refer to as SPLAMs (SPLicing inhibitor sulfonAMides). SPLAMs act by recruiting RBM39 (RNA binding motif 39) as a neo-substrate to DCAF15 (DDB1/CUL Associated Factor 15). DCAF15 is part of a CUL4 E3 ubiquitin ligase receptor complex. As a consequence, recruitment of RBM39 to DCAF15 leads to RBM39 ubiquitination and proteasomal degradation. RBM39 is important for pre-mRNA splicing of select introns and exons. Therefore, as a consequence of SPLAM treatment, RBM39 degradation leads to pre-mRNA splicing defects. The mechanism of action of SPLAMs is similar to the FDA approved drugs, thalidomide and lenalidomide (also known as IMiDs). IMiDs recruit neosubstrates to cereblon, which is another member of the DCAF family of proteins. IMiD binding to CRBN has pleiotropic effects which are either the result of targeting unique neo-substrates or inhibiting the endogenous activity of cereblon. Currently, it is not known as to what effects SPLAM binding to DCAF15 has on alternative neo-substrates and endogenous activity. In our first aim, we propose to identify a DCAF15 mutation that is resistant to SPLAMs in order to identify on-target cellular pathways influenced by SPLAMs. In our second aim, we propose a set of experiments to identify both DCAF15 endogenous substrates as well as neo-substrates other than RBM39. The clinical development of a SPLAM based therapy will require identifying which patients are most likely to respond. We have found that RBM39 degradation only causes cell death in a subset of cancer cells. In our final aim, we propose a set of experiments to understand the basis for this selectivity by studying the function of RBM39 in SPLAM-sensitive and insensitive cells. In particular, our preliminary data suggests that cancer cells with mutations in splicing factors that are also found in human cancers are sensitive to SPLAMs. We propose a set of experiments to study RBM39 biology and SPLAM sensitivity in models of human cancer harboring these splicing mutations.