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

PI 3 K/AKT/mTOR信号通路在肿瘤的发生和发展中起重要作用。PI 3 K/AKT/mTOR异常 在大部分乳腺癌患者中已经记录了过度活化。PI3K/AKT 由于剂量限制性毒性和耐药性的出现，抑制剂在临床上显示出有限的功效。 因此，鉴定AKT上游调节的异常机制和鉴定下游调节的异常机制是可能的。 PI 3 K/AKT信号传递与恶性肿瘤相关的表型的机制仍然至关重要。 表观遗传调节在肿瘤发生中发挥着重要作用，针对表观遗传因素的抑制剂 在临床试验阶段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，无论致癌信号通路， 包括PI 3 K/AKT/mTOR在内的细胞因子的甲基化依赖性调节尚未被探索。我们 初步数据显示，AKT经历赖氨酰甲基化，这是一种新的调节模式，有助于 乳腺癌中的蛋白激酶活化。组蛋白甲基转移酶SETDB 1的消耗降低AKT 活性，表明SETDB 1可能是PI 3 K/AKT驱动的乳腺癌的新治疗靶点。 因此，在目的1中，我们提出乳腺癌中SETDB 1的异常表达有助于 AKT以甲基化依赖性方式过度活化。我们将机械地定义SETDB 1 作为一种新的上游调节机制，促进AKT激活。我们将进一步研究 SETDB 1基因切除是否抑制体外和体内增殖。 已知基因转录、蛋白质翻译和代谢重编程介导 PI 3 K/AKT/mTOR信号在癌症中的作用我们的初步研究发现了一种以前未被发现的 N-糖基转移酶ALG 3（天冬酰胺连接的糖基化3同源物）的作用机制， 在乳腺肿瘤中与PIK 3CA扩增，与乳腺癌中的增殖基因特征密切相关 并且在PI 3 K/AKT/mTOR下游被磷酸化。ALG 3的失调诱导ER应激，导致 未折叠蛋白反应（unfolded protein response，UPR）因此，在目的2中，我们提出ALG 3是一个功能性靶标 PI 3 K/AKT/mTOR/S6 K1信号通路，并且需要该通路的超活化来满足需求。 增加蛋白质翻译，从而减少内质网应激。我们将确定 PI 3 K/mTOR信号调节ALG 3功能并在体外和体内执行功能性糖组学。我们将 确定ALG 3对途径突变细胞生长的贡献，并使用联合治疗 PI 3 K/AKT/mTOR抑制剂和阻断ER应激/UPR的药物。拟议的研究将 为通过抑制肿瘤细胞的增殖来开发更有效的靶向治疗提供了分子基础和理论依据。 PI 3 K/AKT通路基于个体患者的信号传导特征，以实现更好的治疗结果。

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.