通过frenolicin分子探针发现其抑制帽依赖翻译的抗肿瘤作用机制

Cap-dependent translation plays the central role in the proliferation and growth of solid cancer cells including colorectal cancer. Genetic blockade of cap-dependent translation by a non-phosphorylated 4E-BP1 mutant can effectively suppress tumor growth and metastasis in the animal model. Based on the related reporter assay, we recently discovered that the antitumor activity of frenolicin-type pyranonaphthoquinone natural products was adopted from their inhibition of the cap-dependent translation process. The specific mechanism is associated to the inactivating phosphorylation of 4E-BP1, the rate-limiting translational repressor in the formation of cap complex. Since 4E-BP1 phosphorylation function as a critical node to several upstream kinase signals and direct targeting to the 4E-BP1-regulated oncogenes have been limited studied worldwide, herein we proposed to learn the structure-activity relationship between pyranonaphthoquinone natural products and their inhibition of 4E-BP1 phosphorylation on the basis of our total synthetic routes. Next, the objective of this proposed research is to elucidate the direct target(s) and molecular mechanism of action with the design and development of multi-function probes by focusing upon increased potency, selective activity toward 4E-BP1, anti-cancer activity, and reduced general toxicity. These studies would provide novel agents with an expectation to define a new generation of targeted therapies for cap-dependent translation of colorectal cancer progression and potentially other major cancers.

帽依赖翻译是实体肿瘤细胞尤其是结肠癌细胞生长增殖中的核心环节。使用无法磷酸化的变异eIF-4E结合蛋白1（4E-BP1）阻断帽依赖翻译，可以有效地抑制体内模型的肿瘤生长和转移。基于相关筛选模型，我们前期发现以frenolicin为代表的吡喃并萘醌天然产物的抗肿瘤作用主要源于其对帽依赖翻译的抑制。进一步研究发现，本类化合物通过抑制帽复合物形成过程中的限速因子——4E-BP1磷酸化，导致细胞凋亡。由于4E-BP1磷酸化是上游多个激酶信号传导的关键节点，又考虑以其为生物标记物的抗癌作用机制尚缺乏研究，因此本课题拟在对部分本类天然产物全合成基础上，着重研究其和4E-BP1磷酸化的构效关系。应用其构效关系设计和合成多功能的探针分子，并使用探针分子探索本类化合物的作用靶蛋白和具体的上下游分子作用机制。最后基于获得靶蛋白信息，指导进一步的活性和成药性优化，以期获得一类抑制帽依赖翻译的新型抗癌先导化。

本项目前期探索了frenolicin代表的吡喃并萘醌类天然产物合成，经测试发现了吡喃并萘醌类天然产物的抗肿瘤作用主要源于其对帽依赖翻译的抑制；进一步研究发现本类天然产物强抑制4E-BP1磷酸化水平，且与已知cap-dependent translation通路相关调节因子的抑制剂具有不同的作用机制。因此，我们在本项目中主要着眼于，本类化合物抑制4E-BP1磷酸化的作用靶标和机制发现。首先通过开展了多个亚类吡喃并萘醌天然产物分子的全合成研究，全面总结了天然结构的构效关系; 然后设计和制备了亲和探针分子,通过基于亲和作用的蛋白组方法应用探针分子开展靶标垂钓；最终明确了本类化合物抑制结肠癌肿瘤增殖作用的靶蛋白，并据此优化证实了天然结构的主要核心药效团；发现了活性提高的先导化合物，并以结肠癌动物模型尝试使用本类结构开展治疗的可行性。