Targeting Translation Dependence in Colorectal Cancer Progression

项目总结 转移性结直肠癌(CRC)是一种侵袭性疾病，每年影响约50,000人死亡。 美国。转移性结直肠癌患者对现有的治疗方法大多无反应。转移性 这一过程在一定程度上是由致癌mRNAs的失调翻译介导的，导致其过度生产。 编码的蛋白质。先前的发现证实了下游依赖帽的mRNA翻译的失调 4E-BP1/eIF4E水平的mTOR在结直肠癌的形成和转移过程中起关键作用。而当 靶向mTOR被认为是治疗结直肠癌的一种有前途的策略，mTOR的治疗效果有限 抑制药与4E-BP1翻译抑制功能的丧失密切相关。更新的发现 提示Snail是4E-BP1转录的强阻遏子，并与mTOR介导的转录具有协同作用 4E-BP1的磷酸化(失活)显著增加eIF4E启动的帽依赖的mRNA 翻译。这些过程支持了肿瘤的生长，并降低了mTOR激酶(ATP- 竞争性)抑制剂(MTORkis)用于结直肠癌治疗。尽管mTORKis有效地抑制了4E- Bp1并恢复其对帽依赖翻译和肿瘤生长的抑制作用，mTORkis治疗 结直肠癌细胞可促进免疫抑制蛋白PD-L1的主动翻译和表达 以帽不依赖的方式在内部核糖体进入位点(IRES)启动。此外，RNA解旋酶 EIF4A是一个关键的PD-L1 IRES结合蛋白，调节其翻译和表达。重要的是，提升了 MTORKIS诱导的PD-L1水平可导致抗CRC免疫逃避。此外，对PD-L1的靶向抑制 可以恢复T细胞免疫，增强mTORKIS的疗效。根据这些调查结果，中央 这项研究的假设是，结直肠癌细胞篡夺了这两个上限的调节机制。 Snail和mTOR共激活依赖翻译及IRES介导的PD-L1到 在mTOR激酶靶向治疗中逃避免疫监视，从而导致结直肠癌对mTORkis耐药 和促进儿童权利公约的进展。为了验证这一假设，提出了以下具体目标：1)确定 Snail如何与mTOR合作，在翻译控制CRC进展和调制mTOR激酶- 靶向治疗；2)确定PD-L1mRNA翻译对mTOR的非依赖性机制 3)确定共靶向PD-L1和mTOR以加强结直肠癌治疗的体内效用。 这项研究的重点是创新的概念，即Snail和PD-L1都通过 与mTOR合作通过4E-BP1-1的失调调节对mTORkis的治疗反应 中介的翻译启动过程。这项研究不仅将定义两者的新机制角色 Snail和PD-L1在mTOR/4E-BP1介导的结直肠癌进展和转译控制中的作用 抵制mTORKIS，但也促进了理性的方法来开发新的可翻译的 晚期结直肠癌患者的治疗策略。

PROJECT SUMMARY Metastatic colorectal cancer (CRC) is an aggressive disease impacting about 50,000 deaths annually in the USA. Patients with metastatic CRC are predominantly unresponsive to existing therapies. The metastatic process is mediated in part by dysregulated translation of oncogenic mRNAs, leading to overproduction of their encoded proteins. Previous findings established dysregulation of cap-dependent mRNA translation downstream of mTOR at the level of 4E-BP1/eIF4E as a key to tumor formation and metastatic progression in CRC. While targeting mTOR is thought to be a promising strategy for CRC therapy, limited therapeutic efficacy of mTOR inhibitor drugs correlates largely with loss of the translation repressive function of 4E-BP1. More recent findings indicate that Snail acts as a strong repressor of 4E-BP1 transcription and cooperates with mTOR-mediated phosphorylation (inactivation) of 4E-BP1 to significantly increase eIF4E-initiated cap-dependent mRNA translation. These processes support tumor growth and decrease the efficacy of the mTOR kinase (ATP- competitive) inhibitors (mTORkis) in CRC therapy. Although mTORkis effectively inhibit phosphorylation of 4E- BP1 and restore its repressive effects on cap-dependent translation and tumor growth, treatment with mTORkis in CRC cells can promote the active translation and expression of the immunosuppressive protein PD-L1 via initiation at an internal ribosome entry site (IRES) in a cap-independent manner. In addition, the RNA helicase eIF4A is a key PD-L1 IRES binding protein that regulates its translation and expression. Importantly, elevated PD-L1 levels induced by mTORkis result in evasion of anti-CRC immunity. Further, targeted inhibition of PD-L1 can restore T-cell immunity and enhance the efficacy of mTORkis. Based on these findings, the central hypothesis of the proposed study is that CRC cells usurp the regulatory mechanisms underlying both cap- dependent translation through co-activation of Snail and mTOR and IRES-mediated translation of PD-L1 to escape immune surveillance in mTOR kinase-targeted therapy, thereby causing CRC resistance to mTORkis and promoting CRC progression. To test this hypothesis, the following specific aims are proposed: 1) to identify how Snail cooperates with mTOR in translational control of CRC progression and modulation of mTOR kinase- targeted therapy; 2) to determine the cap-independent mechanism of PD-L1 mRNA translation upon mTOR kinase inhibition; and 3) to define the in vivo utility of co-targeting PD-L1 and mTOR to enhance CRC therapy. The focus of this study is the innovative concept that both Snail and PD-L1 promote CRC progression by cooperating with mTOR to modulate therapeutic response to mTORkis through dysregulation of 4E-BP1- mediated translation initiation processes. This research will not only define the novel mechanistic roles of both Snail and PD-L1 in the modulation of mTOR/4E-BP1-mediated translational control of CRC progression and resistance to mTORkis, but also facilitate rational approaches for the development of new translatable therapeutic strategies for patients with advanced CRC.