Recent syntheses of PI3K/Akt/mTOR signaling pathway inhibitors

This review focuses on the syntheses of PI3K/Akt/mTOR inhibitors that have been reported outside of the patent literature in the last 5 years but is largely centered on synthetic work reported in 2011 and 2012. While focused on syntheses of inhibitors, some information on in vitro and in vivo testing of compounds is also included. Many of these reported compounds are reversible, competitive adenosine triphosphate (ATP) binding inhibitors, so given the structural similarities of many of these compounds to the adenine core, this review presents recent work on inhibitors based on where the synthetic chemistry was started, that is, inhibitor syntheses which started with purines/pyrimidines are followed by inhibitor syntheses which began with pyridines, pyrazines, azoles, and triazines then moves to inhibitors which bear no structural resemblance to adenine: liphagal, wortmannin and quercetin analogs. The review then finishes with a short section on recent syntheses of phosphotidyl inositol (PI) analogs since competitive PI binding inhibitors represent an alternative to the competitive ATP binding inhibitors which have received the most attention.     

缺氧诱导因子1与PI3K/Akt/mTOR信号转导通路

缺氧诱导因子1（HIF-1）是参与缺氧调节的核心因子,可调控一系列缺氧诱导基因的表达,与机体许多生理和病理过程也密切相关。尽管一些研究显示缺氧和非缺氧性刺激可通过PI3K/Akt/mTOR信号途径诱导HIF-1的表达和活性,PI3K信号途径是否参与对HIF-1的调节仍然是个有争议的研究热点。明确HIF-1和PI3K的相互作用关系,能进一步为肿瘤等相关疾病的防治提供新的思路和方法。本文主要就HIF-1和PI3K/Akt/mTOR关系作一简要综述。     

Muscone suppresses myocardial ischemia damage by regulating PI3K/Akt signaling pathway

Muscone is the main active compound of Moschus. In this paper, the cardioprotective effect of Muscone on acute myocardial ischemia (AMI) rats and its potential mechanisms were investigated. AMI rat models were established to evaluate the protective effect and antioxidative function of Muscone on the hearts. Moreover, Western blot analysis was conducted to quantify the phosphorylated PI3K and AKT levels in PI3K/Akt pathway for further investigating the mechanism of Muscone. Results showed that Muscone could markedly lessen the infarct size and myocardial injury, improve cardiac function, inhibit cardiomyocyte apoptosis and down-regulate serum reactive oxygen species level as indicated by the decreased MDA, BNP and c-TnI activities and the increased SOD, GSH-px, CAT activities and the expression of Bax protein. In addition, it was revealed that Muscone notably promoted the phosphorylation of PI3K and AKT. These findings denote that Muscone exerts a protective effect in heart via inhibition of oxidative stress and apoptosis, offering new insights into the treatment of CHD and the clinical application of Muscone.     

PI3K/Akt信号通路的调控与肿瘤血管生成

肿瘤对人类的生存危害极大,恶性肿瘤的治疗一直是世界性的难题。肿瘤血管生成是肿瘤赖以生长、转移的基础,受多种因子的调节。目前发现有多条信号网络参与调控肿瘤血管生成,PI3K/Akt是其中比较重要的一条信号传导途径,该通路与肿瘤的发生发展密切相关。本文介绍了PI3K/Akt信号通路的结构组成与活性调控,并重点阐述PI3K/Akt信号途径与肿瘤血管生成的关系。     

PI3K/Akt信号通路与肺纤维化

肺纤维化(pulmonary fibrosis)是进行性、致命性的疾病。其致病机制不明,治疗效果差。PI3K/Akt信号通路主要与细胞的生长、增殖、分化、凋亡及血管形成等有关。近年来,随着对PI3K/Akt信号通路的深入研究,发现其活化后可激活下游中的一些因子参与肺纤维化,且与其他通路协同作用促进肺纤维化的形成。因此该通路有可能成为治疗肺纤维化的新靶点。将PI3K/Akt信号通路参与肺纤维化形成的研究进展作一综述。     

PI3K/Akt/mTOR signaling regulates glutamate transporter 1 in astrocytes

Reduction in or dysfunction of glutamate transporter 1 (GLT1) is linked to several neuronal disorders such as stroke, Alzheimer’s disease, and amyotrophic lateral sclerosis. However, the detailed mechanism underlying GLT1 regulation has not been fully elucidated. In the present study, we first demonstrated the effects of mammalian target of rapamycin (mTOR) signaling on GLT1 regulation. We prepared astrocytes cultured in astrocyte-defined medium (ADM), which contains several growth factors including epidermal growth factor (EGF) and insulin. The levels of phosphorylated Akt (Ser473) and mTOR (Ser2448) increased, and GLT1 levels were increased in ADM-cultured astrocytes. Treatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor or an Akt inhibitor suppressed the phosphorylation of Akt (Ser473) and mTOR (Ser2448) as well as decreased ADM-induced GLT1 upregulation. Treatment with the mTOR inhibitor rapamycin decreased GLT1 protein and mRNA levels. In contrast, rapamycin did not affect Akt (Ser473) phosphorylation. Our results suggest that mTOR is a downstream target of the PI3K/Akt pathway regulating GLT1 expression.     

Trop2 as an oncogene in gastric cancer by regulating PI3K/Akt signaling pathway

High Trop2 expression relates to aggressive tumor behavior and contributes to poor overall survival rates in gastric cancer (GC) patients. However, little is known about the molecular mechanism of Trop2 in the carcinogenesis of GC. We found that over-expressed Trop2 induced cell proliferation and clone formation, inhibited cell apoptosis and induced S cell cycle arrest in GC cell lines, meanwhile, knockdown Trop2 inhibited cell proliferation and clone formation, induced cell apoptosis and inhibits S cell cycle arrest in vitro. Moreover, Trop2 depletion inhibited tumor growth , the anti-tumor rate in this report being 22.53% in vivo. In addition, Trop2 activated the PI3K/Akt signaling pathway to promote GC malignant progression. These results indicated that Trop2 is a critical regulation factor in the progression of GC, which may help to lead a novel insight into understanding the mechanism of the Trop2 in the pathogenesis of GC.     

Role of PI3K/Akt signaling pathway in cardiac fibrosis

Molecular and Cellular Biochemistry - Heart failure (HF) is considered as a severe health problem worldwide, while cardiac fibrosis is one of the main driving factors for the progress of HF....     

Angiogenin interacts with ribonuclease inhibitor regulating PI3K/AKT/mTOR signaling pathway in bladder cancer cells

Angiogenin (ANG), a member of RNase A superfamily, is the only angiogenic factor that possesses ribonucleolytic activity. Recent studies showed that the expression of ANG was elevated in various types of cancers. Accumulating evidence indicates that ANG plays an essential role in cancer progression by stimulating both cancer cell proliferation and tumor angiogenesis. Human ribonuclease inhibitor (RI), a cytoplasmic protein, is constructed almost entirely of leucine rich repeats (LRRs), which are present in a large family of proteins that are distinguished by their display of vast surface areas to foster protein–protein interactions. RI might be involved in unknown biological effects except inhibiting RNase A activity. The experiment demonstrated that RI also could suppress activity of angiogenin (ANG) through closely combining with it in vitro. PI3K/AKT/mTOR signaling pathway exerts a key role in cell growth, survival, proliferation, apoptosis and angiogenesis. We recently reported that up-regulating RI inhibited the growth and induced apoptosis of murine melanoma cells through repression of angiogenin and PI3K/AKT signaling pathway. However, ANG receptors have not yet been identified to date, its related signal transduction pathways are not fully clear and underlying interacting mechanisms between RI and ANG remain largely unknown. Therefore, we hypothesize that RI might combine with intracellular ANG to block its nuclear translocation and regulate PI3K/AKT/mTOR signaling pathway to inhibit biological functions of ANG. Here, we reported for the first time that ANG could interact with RI endogenously and exogenously by using co-immunoprecipitation (Co-IP) and GST pull-down. Furthermore, we observed the colocalization of ANG and RI in cells with immunofluorescence staining under laser confocal microscope. Moreover, through fluorescence resonance energy transfer (FRET) assay, we further confirmed that these two proteins have a physical interaction in living cells. Subsequently, we demonstrated that up-regulating ANG including ANG His37Ala mutant obviously decreased RI expression and activated phosphorylation of key downstream target molecules of PI3K/AKT/mTOR signaling pathway. Finally, up-regulating ANG led to the promotion of tumor angiogenesis, tumorigenesis and metastasis in vivo. Taken together, our data provided a novel mechanism of ANG in regulating PI3K/AKT/mTOR signaling pathway via RI, which suggested a new therapeutic target for cancer therapy.     

Cyclophilin A inhibits A549 cell oxidative stress and apoptosis by modulating the PI3K/Akt/mTOR signaling pathway

The excessive and inappropriate production of reactive oxygen species (ROS) can cause oxidative stress and is implicated in the pathogenesis of lung cancer. Cyclophilin A (CypA), a member of the immunophilin family, is secreted in response to ROS. To determine the role of CypA in oxidative stress injury, we investigated the role that CypA plays in human lung carcinoma (A549) cells. Here, we showed the protective effect of human recombinant CypA (hCypA) on hydrogen peroxide (H₂O₂)-induced oxidative damage in A549 cells, which play crucial roles in lung cancer. Our results demonstrated that hCypA substantially promoted cell viability, superoxide dismutase (SOD), glutathione (GSH), and GSH peroxidase (GSH-Px) activities, and attenuated ROS and malondialdehyde (MDA) production in H₂O₂-induced A549 cells. Compared with H₂O₂-induced A549 cells, Caspase-3 activity in hCypA-treated cells was significantly reduced. Using Western blotting, we showed that hCypA facilitated Bcl-2 expression and inhibited Bax, Caspase-3, Caspase-7, and PARP-1 expression. Furthermore, hCypA activates the PI3K/Akt/mTOR pathway in A549 cells in response to H₂O₂ stimulation. Additionally, peptidyl-prolyl isomerase activity was required for PI3K/Akt activation by CypA. The present study showed that CypA protected A549 cells from H₂O₂-induced oxidative injury and apoptosis by activating the PI3K/Akt/mTOR pathway. Thus, CypA might be a potential target for lung cancer therapy.     

G0S2 represses PI3K/mTOR signaling and increases sensitivity to PI3K/mTOR pathway inhibitors in breast cancer

G0/G1 switch gene 2 (G0S2) is a direct retinoic acid target implicated in cancer biology and therapy based on frequent methylation-mediated silencing in diverse solid tumors. We recently reported that low G0S2 expression in breast cancer, particularly estrogen receptor-positive (ER+) breast cancer, correlates with increased rates of recurrence, indicating that G0S2 plays a role in breast cancer progression. However, the function(s) and mechanism(s) of G0S2 tumor suppression remain unclear. In order to determine potential mechanisms of G0S2 anti-oncogenic activity, we performed genome-wide expression analysis that revealed an enrichment of gene signatures related to PI3K/mTOR pathway activation in G0S2 null cells as compared to G0S2 wild-type cells. G0S2 null cells also exhibited a dramatic decreased sensitivity to PI3K/mTOR pathway inhibitors. Conversely, restoring G0S2 expression in human ER+ breast cancer cells decreased basal mTOR signaling and sensitized the cells to pharmacologic mTOR pathway inhibitors. Notably, we provide evidence here that the increase in recurrence seen with low G0S2 expression is especially prominent in patients who have undergone antiestrogen therapy. Further, ER+ breast cancer cells with restored G0S2 expression had a relative increased sensitivity to tamoxifen. These findings reveal that in breast cancer G0S2 functions as a tumor suppressor in part by repressing PI3K/mTOR activity, and that G0S2 enhances therapeutic responses to PI3K/mTOR inhibitors. Recent studies implicate hyperactivation of PI3K/mTOR signaling as promoting resistance to antiestrogen therapies in ER+ breast cancer. Our data establishes G0S2 as opposing this form of antiestrogen resistance. This promotes further investigation of the role of G0S2 as an antineoplastic breast cancer target and a biomarker for recurrence and therapy response.     

PI3K/Akt信号通路在白藜芦醇抗大鼠缺血/再灌注性心律失常中的作用及机制

目的：探讨磷脂酰肌醇-3-激酶/蛋白激酶B（PI3K/Akt）信号通路在白藜芦醇抗缺血/再灌注性心律失常中的作用及机制。方法：48只健康雄性SD大鼠,取心电图正常者随机分为4组（n=10）：假手术（SC组）组、缺血/再灌注（I/R组）组、白藜芦醇处理（Res处理组）组、PI3K抑制剂LY294002（LY294002组）组。建立大鼠在体心肌缺血/再灌注模型,观察各组心律失常的发生情况及左室血流动力学变化,Western blot法测定心肌组织中蛋白激酶B（Akt）、磷酸化蛋白激酶B（p-Akt）、缝隙连接蛋白43（Cx43）蛋白表达水平,以RT-PCR法从转录水平检测Cx43的表达水平。结果：与I/R组相比,Res处理组心律失常的发生率（心律失常评分）明显降低、左室舒缩功能明显升高,同时心肌Akt、Cx43蛋白表达及Cx43mRNA水平也明显升高;使用PI3K抑制剂LY294002后,心肌Akt、Cx43蛋白表达及Cx43mRNA水平下降的同时心律失常的发生率明显升高、左室舒缩功能明显降低。结论：白藜芦醇的抗再灌注性心律失常作用可能是通过激活PI3K/Akt信号通路,改变Cx43活性及分布实现的。     

PDGF-AA promotes cell-to-cell communication in osteocytes through PI3K/Akt signaling pathway

Osteocytes are the main sensitive cells in bone remodeling due to their potent functional cell pro-cesses from the mineralized bone matrix to the bone surface a...     

A new role for the PI3K/Akt signaling pathway in the epithelial-mesenchymal transition

Tumor metastasis is not only a sign of disease severity but also a major factor causing treatment failure and cancer-related death. Therefore, studies on the molecular mechanisms of tumor metastasis are critical for the development of treatments and for the improvement of survival. The epithelial-mesenchymal transition (EMT) is an orderly, polygenic biological process that plays an important role in tumor cell invasion, metastasis and chemoresistance. The complex, multi-step process of EMT involves multiple regulatory mechanisms. Specifically, the PI3K/Akt signaling pathway can affect the EMT in a variety of ways to influence tumor aggressiveness. A better understanding of the regulatory mechanisms related to the EMT can provide a theoretical basis for the early prediction of tumor progression as well as targeted therapy.     

Germacrone improves liver fibrosis by regulating the PI3K/AKT/mTOR signalling pathway

Liver fibrosis is a primary threat to public health, owing to limited therapeutic options. Germacrone (GM) has been shown to exert various curative effects against human diseases, including liver injury. The aim of this study was to investigate the pharmacological effects of GM in the pathophysiology of hepatic fibrosis and determine its potential mechanisms of action. A liver fibrosis rat model was established via carbon tetrachloride (CCl₄) treatment, and LX-2 cells were stimulated with TGF-β1. The effects of GM on liver fibrosis and its relationship with the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signalling pathway were investigated. In the CCl₄ fibrosis-induced rat model, GM improved histological damage, inhibited the activity of hepatic α-smooth muscle actin and improved serum alanine aminotransferase and aspartate aminotransferase levels in a dose-dependent manner. GM potently inhibited hepatic stellate cells (HSCs) growth and epithelial–mesenchymal transition (EMT) progression, as reflected by the altered expression of proliferative (Ki-67, PCNA and cleaved caspase-3) and EMT-related (E-cadherin and vimentin) proteins. In TGF-β1-stimulated LX-2 cells, GM significantly inhibited the survival and activation of HSCs and induced cell apoptosis. GM also suppressed the migration ability and reversed the EMT process in HSCs. Following GM treatment, the phosphorylation of the PI3K, AKT and mTOR proteins was reduced in the liver of CCl₄-treated rats and TGF-β1-stimulated LX-2 cells, indicating that GM may attenuate hepatic fibrosis via the PI3K/AKT/mTOR signalling pathway. These outcomes highlight the anti-fibrotic effects of GM and suggest that it is a potential therapeutic agent for the treatment of liver fibrosis.     

Melatonin protects against methotrexate hepatotoxicity in young rats: Impact of PI3K/Akt/mTOR signaling

With the improvement in children's acute lymphoblastic leukemia (ALL) care, the survival rate in children ALL has improved much. Methotrexate (MTX) plays an essential role in the success of children's ALL treatment. Since hepatotoxicity is commonly reported in individuals treated with intravenous or oral MTX, our study further examined the hepatic effect following intrathecal MTX treatment, which is an essential treatment for leukemia patients. Specifically, we examined the pathogenesis of MTX hepatotoxicity in young rats and explored the impact of melatonin treatment in protection against MTX hepatotoxicity. Successfully, we found that melatonin was able to protect against MTX hepatotoxicity.     

PI3K/Akt信号传导通路与肿瘤

信号转导通路的异常激活是肿瘤细胞的发生、发展重要步骤,PI3K/Akt 信号通路在人类绝大多数恶性肿瘤中被异常激活,其在肿瘤的增殖、存活、细胞运动、抵抗凋亡、血管发生和转移以及对化疗耐药、放疗抗拒中发挥了重要作用.因此,通过对PI3K/Akt 通路的研究进一步了解肿瘤的发生、发展机制,并寻求抗肿瘤药物的新靶点,本文就 PI3K/Akt 信号转导通路的结构特点、与肿瘤发生、发展的关系及其时放化疗的影响作一综述.