Mechanisms of PIK3CA helical domain mutations driving colorectal tumorigenesis

该提案的总体目标是开发PIK 3CA突变型结直肠癌的精确治疗。 （CRC）。磷脂酰肌醇3-激酶（PI 3 K）是由p110催化亚基和p85催化亚基组成的异源二聚体。 调节亚单位本申请的PI共同发现，编码p110α的PIK 3CA经常被 在多种人类癌症中突变，包括约30%的CRC。大多数PIK 3CA/p110α致癌突变发生在 在两个热点区域，一个在螺旋结构域，另一个在激酶结构域。几乎一半的p110α 突变位于螺旋结构域中。越来越多的证据表明，螺旋结构域和激酶 突变通过不同的机制发挥其致癌功能。对于螺旋结构域突变，我们 发现致癌信号是通过两条独特的途径传递的。我们以前发现p110α 螺旋结构域突变蛋白不依赖于p85而直接与IRS 1结合以激活PI 3 K α-AKT。现在我们的 初步研究表明，p85β与p110α螺旋结构域突变蛋白分离 复合并转移到细胞核中。核p85β稳定EZH 1和EZH 2，这两种酶 催化组蛋白H3 K27三甲基化。值得注意的是，我们发现EZH抑制剂GSK 126与 p110α特异性抑制剂Alpelisib诱导含有PIK 3CA螺旋结构域的CRC肿瘤消退 突变因此，我们推测核p85β促进p110α螺旋结构域的致癌功能 突变，同时抑制核p85β功能和p110α激酶将是有效的 治疗具有螺旋结构域突变的肿瘤的方法。提出了两个目标来检验中心假设： 1)阐明核p85β促进PIK 3CA螺旋结构域致癌功能的机制 突变;和2）使用一组CRC突变确定GSK 126和Alpelisib的组合的功效。 具有PIK 3CA螺旋结构域突变的患者来源的异种移植物。成功完成学业将 证明GSK 126和Alpelisib的组合作为具有PIK 3CA螺旋的CRC的有效治疗 结构域突变的临床前模型，并奠定了坚实的基础，为未来的临床试验。此外，我们的研究 揭示p85β核转位是PIK 3CA螺旋结构域突变发挥其作用的新机制。 致癌功能

The overarching goal of this proposal is to develop precision therapy for PIK3CA-mutant colorectal cancer (CRC). Phosphatidylinositol 3-kinases (PI3K) are heterodimers consisting of a p110 catalytic subunit and a p85 regulatory subunit. The PI of this application co-discovered that PIK3CA, which encodes p110α, is frequently mutated in a variety of human cancers, including ~30% of CRC. Most PIK3CA/p110α oncogenic mutations occur at two hot spot regions, one in the helical domain and the other in the kinase domain. Nearly half of all p110α mutations are located in the helical domain. Increasing evidence suggests that the helical domain and kinase mutations exert their oncogenic function through distinct mechanisms. For the helical domain mutations, we discovered that the oncogenic signal is transduced by two unique pathways. We previously found that the p110α helical domain mutant protein directly associates with IRS1 independent of p85 to activate PI3Kα-AKT. Now, our preliminary studies demonstrate that p85β disassociates from the p110α helical domain mutant protein complexes and translocates into the nucleus. The nuclear p85β stabilizes EZH1 and EZH2, two enzymes that catalyze histone H3K27 trimethylation. Remarkably, we found that a combination of EZH inhibitor GSK126 with a p110α-specific inhibitor Alpelisib induced tumor regression of CRCs harboring a PIK3CA helical domain mutation. Thus, we hypothesize that nuclear p85β promotes oncogenic functions of p110α helical domain mutations and that simultaneous inhibition of both nuclear p85β function and p110α kinase will be an effective approach to treat tumors with a helical domain mutation. Two aims are proposed to test the central hypothesis: 1) elucidate the mechanisms by which nuclear p85β promotes oncogenic functions of PIK3CA helical domain mutations; and 2) determine the efficacy of the combination of GSK126 and Alpelisib using a panel of CRC patient-derived xenografts with a PIK3CA helical domain mutation. Successful completion of our studies will demonstrate the combination of GSK126 and Alpelisib as an effective treatment for CRCs with PIK3CA helical domain mutations in preclinical models and lay a solid foundation for future clinical trials. Moreover, our studies uncover p85β nuclear translocation as a novel mechanism by which PIK3CA helical domain mutations exert their oncogenic functions.