Selectively targeting apoptosis in PIK3CA mutant colorectal cancers

项目摘要 大约20%的结直肠癌（CRC），代表美国每年25，000例患者， 激活PIK 3CA基因中的驱动突变，该基因编码PIK 3CA的催化α亚基， 磷脂酰肌醇-3-激酶（PI 3 K）。这些患者在接受 标准的护理化疗，也未能响应PI 3 K通路的单药抑制剂， 这一问题强调了对PIK 3CA突变体更有效的治疗策略的迫切需要。 《儿童权利公约》。最近，通过将来自人类CRC患者的磷酸化蛋白质组学数据与组合药物组合相结合， 在CRC细胞系中筛选时，我们发现细胞外信号调节激酶（ERK）的抑制剂 途径选择性地使PIK 3CA突变CRC对酪氨酸激酶SRC的抑制剂敏感，而不考虑 其他常见突变基因的突变状态，包括KRAS和BRAF。通过机械 研究表明，该组合对PIK 3CA突变型CRC的选择性归因于（1）SRC的 仅在PIK 3CA突变细胞中选择性激活，其中其药理学抑制与ERK协同作用 途径抑制通过诱导促凋亡蛋白BIM触发凋亡，和（2）事实上 PIK 3CA突变型CRC对由组成性PI 3 K激活驱动的慢性BIM抑制“上瘾”， 因此比它们的PIK 3CA野生型对应物对BIM诱导更加敏感。收购 对SRC和ERK通路抑制剂组合的抗性集中在抗- 凋亡蛋白BCL-XL，其直接拮抗BIM。BCL-XL的前期抑制与 SRC和ERK途径抑制导致渗透细胞杀伤，同时阻断获得性细胞凋亡的出现。 阻力在本建议中，我们通过一系列综合研究，以这些发现为基础，研究（1） PIK 3CA突变体中SRC激活及其与ERK通路协同作用的分子机制 CRC;（2）联合SRC加ERK通路抑制的翻译潜力，使用患者研究- 衍生的异种移植物（PDX）模型以及人患者肿瘤中的相关临床研究;和（3）所述方法， BCL-XL抑制逆转或阻断获得性耐药性的能力，以及阐明 抵抗状态下BCL-XL激活的机制。这项工作将定义一个基本的生存 PIK 3CA突变型CRC中的信号网络，并有望成为第一个选择性靶向治疗药物 针对这种侵袭性疾病亚型的策略。

Project Summary Approximately 20% of colorectal cancers (CRCs), representing 25,000 patients in the U.S. each year, harbor activating driver mutations in the PIK3CA gene, which encodes the catalytic alpha subunit of phosphatidylinositol-3-kinase (PI3K). These patients have particularly poor prognoses when treated with standard-of-care chemotherapies and also fail to respond to single agent inhibitors of the PI3K pathway, a problem that underscores the compelling need for more effective therapeutic strategies for PIK3CA mutant CRC. Recently, by combining phosphoproteomic data from human CRC patients with combinatorial drug screening in CRC cell lines, we discovered that inhibitors of the extracellular signal-regulated kinase (ERK) pathway selectively sensitize PIK3CA mutant CRCs to inhibitors of the tyrosine kinase SRC without regard to the mutational status of other commonly mutated genes, including KRAS and BRAF. Through mechanistic studies, it was revealed that the selectivity of this combination for PIK3CA mutant CRCs owes to (1) SRC's selective activation only in PIK3CA mutant cells, where its pharmacological inhibition cooperates with ERK pathway inhibition to trigger apoptosis through the induction of the pro-apoptotic protein BIM, and (2) the fact that PIK3CA mutant CRCs are “addicted” to chronic BIM suppression driven by constitutive PI3K activation, and are thus vastly more sensitive to BIM induction than their PIK3CA wild-type counterparts. Acquired resistance to combinations of SRC and ERK pathway inhibitors converges on the activation of the anti- apoptotic protein BCL-XL, which directly antagonizes BIM. Upfront inhibition of BCL-XL in combination with SRC and ERK pathway inhibition leads to penetrant cell killing while blocking the emergence of acquired resistance. In this proposal, we build on these findings through a series of integrated studies examining (1) the molecular mechanisms governing SRC activation and its cooperation with the ERK pathway in PIK3CA mutant CRC; (2) the translational potential of combined SRC plus ERK pathway inhibition using studies in patient- derived xenograft (PDX) models alongside correlative clinical studies in human patient tumors; and (3) the ability of BCL-XL inhibition to reverse or block acquired resistance, alongside studies to elucidate the molecular mechanisms governing BCL-XL activation in the resistant state. The work will define an essential survival signaling network in PIK3CA mutant CRC and is expected to lead to the first selective targeted therapeutic strategies for this aggressive disease subtype.