Natural product-based modulators of 4E-BP1 phosphorylation

 描述(申请人提供)：转移性结直肠癌(CRC)很难治疗，患者几乎没有长期有效的治疗选择。这种疾病的侵袭性在一定程度上是由癌蛋白的异常表达驱动的。在分子水平上，前体致癌mRNAs的帽子依赖翻译经常被激活。具体地说，这是通过4E-BP1磷酸化实现的，当4E-BP1未被磷酸化时，它作为mTOR下游的mRNA翻译抑制因子发挥作用。我们最近发现，通过PI3K/AKT和RAS/RAF/MEK/ERK通路激活的信号通过4E-BP1的收敛磷酸化协同促进CRC的进展。我们的工作进一步证明，4E-BP1磷酸化介导的癌基因翻译是整合AKT和ERK途径的致癌信号在结直肠癌发生和转移中的关键节点。此外，我们发现，结直肠癌对上游激酶靶向治疗的耐药性与不完全抑制4E-BP1的磷酸化有关。值得注意的是，显性活性和非磷酸化的4E-BP1突变体对帽依赖翻译的遗传阻断可以有效地抑制结直肠癌小鼠模型中的肿瘤生长和转移。我们的主要假设是，直接靶向4E-BP1磷酸化介导的癌基因翻译代表了癌症药物开发和治疗的一种新策略。使用帽依赖的翻译为基础的报告实验，我们最近确定了自然存在的吡喃并萘醌类化合物作为4E-BP1磷酸化的选择性抑制剂，其机制与现有的mTOR抑制剂不同。本研究的主要目的是确定吡喃并萘醌类化合物抑制4E-BP1磷酸化的基本机制，并确定具有合适的体内外活性和选择性的优化类似物。总而言之，所提出的研究为鉴定和开发结构和功能上的新药以靶向控制结直肠癌进展和转移提供了很高的潜力，并有可能为治疗结直肠癌的一流靶向治疗定义新的分子探针和早期先导。

 DESCRIPTION (provided by applicant): Metastatic colorectal cancer (CRC) is difficult to treat and patients have few long term effective therapeutic options. The aggressiveness of this disease is in part driven by the aberrant expression of oncoproteins. At the molecular level, cap-dependent translation of the precursor oncogenic mRNAs is frequently activated. Specifically this occurs via 4E-BP1 phosphorylation which, when not phosphorylated, functions as a mRNA translation repressor downstream from mTOR. We recently discovered that activated signaling via the PI3K/AKT and RAS/RAF/MEK/ERK pathways cooperate to promote CRC progression by convergent phosphorylation of 4E-BP1. Our work further demonstrated that 4E-BP1 phosphorylation-mediated oncogene translation functions as a critical node that integrates oncogenic signals of the AKT and ERK pathways for CRC tumorigenesis and metastasis. Moreover, we found that CRC resistance to upstream kinase targeted therapy is associated with incomplete inhibition of 4E-BP1 phosphorylation. Notably, genetic blockade of cap-dependent translation by a dominant active and non-phosphorylated 4E-BP1 mutant can effectively suppress tumor growth and metastasis in the mouse models of CRC. Our overarching hypothesis is that directly targeting 4E-BP1 phosphorylation- mediated oncogene translation represents a novel strategy for cancer drug development and therapy. Using a cap-dependent translation-based reporter assay, we recently identified naturally occurring pyranonaphthoquinones that act as selective inhibitors of 4E-BP1 phosphorylation in a manner that is mechanistically distinct to existing mTOR inhibitors. The primary goals of the proposed studies are to determine the fundamental mechanism of pyranonaphthoquinone-based inhibition of 4E-BP1 phosphorylation and identify optimized analogs with suitable in vitro and in vivo potency and selectivity. Cumulatively, the proposed studies offer high potential for the identification and development of structurally and functionally novel agents to target the translational control of CRC progression and metastasis with the potential to define new molecular probes and early stage leads for first-in-class targeted therapies to treat CRC.