Novel regulation of PI3K/Akt to direct targeted breast cancer therapies

PI3K/AKT/mTOR信号转导通路在肿瘤的发生发展中起重要作用。异常的PI3K/AKT/mTOR 有证据表明，在很大比例的乳腺癌患者中存在过度激活。然而，PI3K/AKT 由于剂量限制毒性和出现耐药性，抑制剂在临床上显示出有限的疗效。 因此，AKT上游调控异常机制的鉴定和下游调控机制的鉴定 PI3K/AKT信号依赖于与恶性肿瘤相关的表型的机制仍然很关键。 表观遗传调控在肿瘤发生中起着重要作用，靶向表观遗传因子的抑制物有 在临床试验中。组蛋白和非组蛋白的甲基化已被证明在功能上起作用 在包括乳腺癌在内的人类癌症中起着关键作用。然而，无论是致癌信号通路， 包括PI3K/AKT/mTOR，都受到甲基化依赖的调控尚未被探索。我们的 初步数据显示，AKT经历赖氨酰甲基化，这是一种新的调控模式，有助于 蛋白激酶在乳腺癌中的激活。组蛋白甲基转移酶SETDB1缺失可降低AKT 提示SETDB1可能成为PI3K/AKT驱动的乳腺癌的一个新的治疗靶点。 因此，在目标1中，我们提出SETDB1在乳腺癌中的异常表达有助于 AKT以甲基化依赖的方式过度激活。我们将机械地定义SETDB1如何 作为一种新的上游调节机制，促进AKT的激活。我们将进一步研究 SETDB1基因消融在体外和体内是否抑制增殖。 基因转录、蛋白质翻译和代谢重编程是已知的中介作用 PI3K/AKT/mTOR信号与肿瘤我们的初步研究发现了一种以前未被认识到的 机制，其中N-糖基转移酶ALG3(天冬酰胺连接的糖基化3同源)是共同的- 在乳腺癌中用PIK3CA扩增，与乳腺癌中的增殖基因标志密切相关 并且在PI3K/AKT/mTOR下游被磷酸化。ALG3的解除调控诱导内质网应激导致 激活未折叠蛋白反应(UPR)。因此，在目标2中，我们提出ALG3是一个功能靶点 PI3K/AKT/mTOR/S6K1信号通路的过度激活 增加蛋白质翻译，从而减少内质网应激。我们将确定通过什么机制 PI3K/mTOR信号调节ALG3的功能，并在体内和体外进行功能性的糖组分。我们会 确定ALG3对途径突变细胞生长的贡献并使用联合治疗 使用PI3K/AKT/mTOR抑制剂和阻断内质网应激/UPR的药物的方法。拟议的研究将 为开发更有效的靶向治疗提供分子基础和理论基础 PI3K/AKT通路基于个体患者的信号特征，以达到更好的治疗效果。

PI3K/AKT/mTOR signaling is critical for the cancer initiation and progression. Aberrant PI3K/AKT/mTOR hyperactivation has been documented in a large proportion of breast cancer patients. However, PI3K/AKT inhibitors have shown limited efficacy in the clinic, due to dose-limiting toxicities and emergence of resistance. Thus, identification of aberrant mechanisms of upstream regulation of AKT and identification of downstream mechanisms of PI3K/AKT signal relay to phenotypes associated with malignancy, remains critical. Epigenetic regulation plays an important role in tumorigenesis, and inhibitors targeting epigenetic factors are in clinical trials. Methylation of histones as well as non-histone proteins has been shown to play a functionally pivotal role in human cancers, including breast cancer. However, whether oncogenic signaling pathways, including PI3K/AKT/mTOR, are subject to methylation-dependent regulation has not been explored. Our preliminary data show that AKT undergoes lysyl methylation, a novel mode of regulation that contributes to protein kinase activation in breast cancer. Depletion of the histone methyltransferase SETDB1 reduces AKT activity, suggesting that SETDB1 could be a novel therapeutic target for PI3K/AKT-driven breast cancers. Therefore, in Aim 1 we propose that aberrant expression of SETDB1 in breast cancer contributes to hyperactivation of AKT in a methylation-dependent manner. We will define mechanistically how SETDB1 functions as a novel upstream regulatory mechanism that promotes AKT activation. We will further examine whether genetic ablation of SETDB1 suppresses proliferation in vitro and in vivo. Gene transcription, protein translation and metabolic reprogramming are known to mediate PI3K/AKT/mTOR signaling in cancer. Our preliminary studies have uncovered a previously unrecognized mechanism, whereby the N-glycosyl transferase ALG3 (asparagine-linked glycosylation 3 homolog), is co- amplified with PIK3CA in breast tumors, tightly correlates with a proliferative gene signature in breast cancers and is phosphorylated downstream of PI3K/AKT/mTOR. Deregulation of ALG3 induces ER stress leading to activation of the unfolded protein response (UPR). Thus, in Aim 2, we propose that ALG3 is a functional target of PI3K/AKT/mTOR/S6K1 signaling, and that hyperactivation of this pathway is required to meet the demands of increased protein translation, thereby reducing ER stress. We will determine the mechanism by which PI3K/mTOR signaling regulates ALG3 function and perform functional glycomics in vitro and in vivo. We will determine the contribution of ALG3 to growth in pathway-mutant cells and use combination therapy approaches with PI3K/AKT/mTOR inhibitors and drugs that block ER stress/UPR. The proposed studies will provide the molecular basis and rationale for developing more effective targeted therapies by suppressing the PI3K/AKT pathway based on individual patients’ signaling signatures to achieve better treatment outcome.