mTOR通路与胃癌的研究进展

哺乳动物雷帕霉素靶蛋白(mTOR)信号转导通路在肿瘤的形成和发展中扮演着非常重要的角色,并参与肿瘤的侵袭和转移。此信号通路于胃癌中高度激活,调控细胞增殖、凋亡、转录、翻译、代谢等细胞生物学过程。本文对mTOR信号传导通路、在胃癌发生发展中的作用及mTOR抑制剂在胃癌治疗中的最新进展进行综述。     

mTOR抑制剂放疗增敏的研究进展

放疗是肿瘤的重要治疗手段之一,仍有部分患者在接受放疗后存在复发或抗拒。哺乳动物雷帕霉素靶蛋白（mammalian target of rapamycin,mTOR）是PI3K/AKT信号通路的主要效应分子,分为mTORC1和mTORC2,对细胞生长及增殖、细胞周期进展及蛋白翻译等均有重要调节作用。mTOR异常表达与肿瘤发生及治疗反应密切相关。肿瘤的放疗敏感性与“4R”效应有关。mTOR抑制剂可通过影响细胞周期进展、DNA损伤修复及抗血管形成等多种途径发挥放疗增敏作用。初期研究证实依维莫司具有放疗增敏作用并且毒性可耐受。应用mTOR抑制剂后不同细胞及个体反应不同,可能与基因表达状态有关,需进一步研究证实。      

mTOR抑制剂在乳腺癌内分泌治疗耐药中的研究进展

PI3K/Akt/mTOR信号转导通路可抑制肿瘤细胞凋亡、促进细胞生存、调节细胞周期,促进肿瘤新生血管的形成以及侵袭与转移,在肿瘤的发生、发展、治疗及转归中发挥着重要作用。该信号通路与乳腺癌关系非常密切,是乳腺癌新的治疗靶点及研究热点。mTOR抑制剂通过不同的靶点作用于PI3K/Akt/mTOR信号转导通路上,从而达到其抗癌作用。内分泌治疗是乳腺癌的重要治疗方式之一,与化疗等其他治疗方式一样,内分泌治疗同样也面临治疗耐受这一难题。随着越来越多的信号通路被揭示,单一阻断某一位点已经不能满足治疗的需要,寻找多条通路的共同抑制位点成为研究人员关注的焦点。本文就mTOR抑制剂在乳腺癌内分泌治疗耐药中的作用及其临床试验结果进行综述,以期进一步了解mTOR抑制剂的临床作用。      

哺乳动物雷帕霉素靶蛋白信号通路与大肠癌

哺乳动物雷帕霉素靶蛋白(mTOR)信号通路作为细胞内重要信号转导通路之一,通过影响下游多种效应分子的活化状态,调节细胞存活、增殖、转分化、迁移和细胞周期.mTOR这些调节机制的异常与大肠癌的发生和发展密切相关.目前mTOR抑制剂治疗大肠癌已处于临床试验中,并取得了一定的进展.     

mTOR信号通路调控CD133阳性胶质瘤干细胞自我更新的分子机制

背景与目的：mTOR（mammalian target of rapamycin）信号通路异常活化和高级别胶质瘤患者的预后不良相关。本研究探讨mTOR信号通路调控胶质瘤干细胞（GSCs）自我更新相关的分子机制。方法：采用CD133免疫磁珠分选CD133阳性胶质瘤干细胞。Western blot检测mTOR信号通路组分p-S6K、p-S6和干细胞自我更新相关基因Bmi-1的表达水平;Rapamycin（RPA）阻断mTOR信号通路后,用肿瘤球形成实验评价干预mTOR信号通路对胶质瘤干细胞自我更新的影响;统计学处理采用SPSS11.0统计分析软件分析。结果：CD133阳性胶质瘤干细胞表达较高水平的mTOR信号通路组分p-S6K、p-S6和干细胞自我更新相关分子Bmi-1。通过rapamycin阻断mTOR信号通路,可诱导胶质瘤干细胞谱系分化,同时显著降低肿瘤球形成能力（P〈0.05）,而自噬抑制剂3-MA处理不能逆转rapamycin的效应。结论：mTOR信号通路能够调控胶质瘤干细胞自我更新,阻断mTOR通路下调胶质瘤干细胞自我更新潜能。     

联合靶向mTOR和Gli1/2信号通路的药物对肾癌细胞生长的抑制效应

目的:探讨联合靶向mTOR和Gli1/2信号通路的药物对肾癌细胞生长的抑制效应。方法:采用Real time-PCR的方法检测SHH/Gli信号通路的核心效应成分Gli1和Gli2在20对正常肾脏和肾癌组织中的表达情况;采用Western blot技术验证4对正常肾脏和配对的肿瘤中Gli1和Gli2蛋白的表达水平。单独或联合使用不同浓度的mTOR抑制剂与Gli1/2抑制剂于肾癌细胞后,采用MTT的方法检测细胞的体外增殖能力,然后采用Western blot技术检测联合应用低剂量mTOR抑制剂与Gli1/2抑制剂的肾癌细胞内细胞周期、凋亡相关蛋白的变化情况。结果:Gli1与Gli2在肾癌组织中的表达高于对照的正常肾脏组织。低剂量（5 μmol/L）Gli1/2抑制剂Gant61并不能显著抑制肾癌细胞的生长,高剂量（10 μmol/L）的Gant61能达到有效的抑制效应;但5 μmol/L Gant61与低剂量mTOR抑制剂Rapamycin联用时,肾癌细胞的生长显著被抑制,且诱导细胞凋亡,阻滞细胞周期。结论:联合靶向mTOR和Gli1/2信号通路显著抑制肾癌细胞生长,为潜在的治疗策略。     

PI3K／Akt／inTOR信号传导通路与恶性肿瘤浸润和转移的研究进展

PI3K／Akt／mTOR信号通路作为细胞内重要信号传导通路之一,通过影响下游多种效应分子的活化状态,在细胞内发挥着抑制凋亡、促进增殖的关键作用,它与人类多种肿瘤的发生发展密切相关。本文综述了PI3K／Akt／mTOR信号通路的组成与功能、调节以及其抗肿瘤细胞凋亡作用机理等方面的研究进展,并就其抗细胞凋亡作用在肿瘤治疗中的应用作了评述,期待为以PI3K／Akt／mTOR信号通路中关键分子为靶点的肿瘤治疗研究提供参考。     

mTOR通路及其抑制剂抗肿瘤的研究进展

哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)是PI3K/Akt通路的下游分子,可接受生长因子、营养、能量等多种信号,是细胞生长和增殖的关键调节分子.许多肿瘤中存在有编码mTOR信号通路相关蛋白的基因突变,这些蛋白的异常表达可引起mTOR通路的过度激活.目前,以mTOR为治疗靶点成为肿瘤治疗的研究新热点.本文就近年来有关mTOR通路及其抑制剂在抗肿瘤方面的研究进展作一综述.     

P53蛋白介导mTOR信号途径影响肿瘤细胞自噬的研究进展

自噬是机体内的一种代谢方式,参与调控多种生理病理过程,受不同信号级联反应调节,在维持细胞生长与代谢等方面起关键作用。哺乳动物雷帕霉素靶蛋白（mammalian target of rapamycin,mTOR）是一种蛋白激酶,也是调节细胞生长和增殖的重要信号分子,其通路的异常激活与肿瘤的发生发展密切相关且可通过调节细胞自噬治疗肿瘤。 p53 为抑癌基因,具有抑制癌症形成的作用。近来研究显示,胞质和胞核中均存在P53蛋白,在核内P53可通过活化腺苷酸活化的蛋白激酶（adenosine monophosphate activated protein kinase,AMPK）激活抑癌基因与张力蛋白同源10q丢失的磷酸酶基因（phosphatase and tensin homolog deleted on chromosome ten,PTEN）的转录等机制来调节mTOR信号通路相关分子,抑制mTOR活性,促使UNC-51激酶1（unc-51-like kinase1,ULK1）去磷酸化而增强自噬,亦可介导某些凋亡蛋白（Bcl-2、Bax等）及调控因子（DRAM、PUMA等）的信号通路参与自噬调节,但与mTOR通路的关系尚待研究;细胞质中的P53蛋白以非依赖转录的方式如降解P53、抑制RB1CC1/FIP200活性等,参与mTOR途径调控,抑制自噬。本文就P53蛋白介导mTOR信号途径影响肿瘤细胞自噬的研究进展作一综述。     

CDK4/6抑制剂联合mTOR抑制剂在乳腺癌中的作用机制

CDK-RB-E2F通路和PI3K-AKT-mTOR通路对乳腺癌耐药机制起到了关键作用。通过对两个通路的研究发现,在治疗激素受体阳性的乳腺癌时,CDK4/6抑制剂与内分泌药物联合使用可以提高患者的生存率,mTOR抑制剂也显示出抗肿瘤的实力。最近的研究表明,mTOR抑制剂和CDK4/6抑制剂联合使用可以进一步抑制CDK-RB-E2F通路激活,协同控制肿瘤细胞增殖。同时发现CDK4/6抑制剂耐药患者的CDK-RB-E2F通路重新激活,仍对mTOR抑制剂敏感。还有研究表明CDK4/6抑制剂和mTOR抑制剂可以通过自噬作用协同控制肿瘤的发生。本文针对两药联合在乳腺癌中的作用机制进行综述。     

mTOR inhibitors in cancer therapy

The mammalian target of rapamycin (mTOR) plays a key role in regulation of cellular metabolism, growth, and proliferation. The frequent hyperactivation of mTOR signaling makes it an attractive target for therapeutic intervention and has driven the development of a number of mTOR inhibitors. Encouraging data from preclinical studies have resulted in initiation of multiple clinical trials. Furthermore, combinational strategies are being studied in an effort to overcome resistance and enhance efficacy. Although additional studies are required to determine their specific role in the clinical setting, mTOR inhibitors remain a promising therapeutic option for the treatment of cancer.     

Current development of the second generation of mTOR inhibitors as anticancer agents

The mammalian target of rapamycin (mTOR), a serine/threonine protein kinase, acts as a "master switch" for cellular anabolic and catabolic processes, regulating the rate of cell growth and proliferation. Dysregulation of the mTOR signaling pathway occurs frequently in a variety of human tumors, and thus, mTOR has emerged as an important target for the design of anticancer agents. mTOR is found in two distinct multiprotein complexes within cells, mTORC1 and mTORC2. These two complexes consist of unique mTOR-interacting proteins and are regulated by different mechanisms. Enormous advances have been made in the development of drugs known as mTOR inhibitors. Rapamycin, the first defined inhibitor of mTOR, showed effectiveness as an anticancer agent in various preclinical models. Rapamycin analogues (rapalogs) with better pharmacologic properties have been developed. However, the clinical success of rapalogs has been limited to a few types of cancer. The discovery that mTORC2 directly phosphorylates Akt, an important survival kinase, adds new insight into the role of mTORC2 in cancer. This novel finding prompted efforts to develop the second generation of mTOR inhibitors that are able to target both mTORC1 and mTORC2. Here, we review the recent advances in the mTOR field and focus specifically on the current development of the second generation of mTOR inhibitors as anticancer agents.     

mTOR pathway in colorectal cancer: an update

The mammalian target of rapamycin (mTOR) has emerged as a potential target for drug development, particularly due to the fact that it plays such a crucial role in cancer biology. In addition, next-generation mTOR inhibitors have become available, marking an exciting new phase in mTOR-based therapy. However, the verdict on their therapeutic efectiveness remains unclear. Here we review phosphatidylinositol-3-kinase (PI3K)/Akt/mTOR signaling as one of the primary mechanisms for sustaining tumor outgrowth and metastasis, recent advances in the development of mTOR inhibitors, and current studies addressing mTOR activation/inhibition in colorectal cancer (CRC). We will also discuss our recent comparative study of diferent mTOR inhibitors in a population of colon cancer stem cells (CSCs), and current major challenges for achieving individualized drug therapy using kinase inhibitors.     

New Insights into mTOR Signal Pathways in Ovarian-Related Diseases: Polycystic Ovary Syndrome and Ovarian Cancer

mTOR, the mammalian target of rapamycin, is a conserved serine/threonine kinase which belongs to the phosphatidyl-linositol kinase-related kinase (PIKK) family. It has two complexes called mTORC1 and mTORC2. It is well established that mTOR plays important roles in cell growth, proliferation and differentiation. Over-activation of the mTOR pathway is considered to have a relationship with the development of many types of diseases, including polycystic ovary syndrome (PCOS) and ovarian cancer (OC). mTOR pathway inhibitors, such as rapamycin and its derivatives, can directly or indirectly treat or relieve the symptoms of patients suffering from PCOS or OC. Moreover, mTOR inhibitors in combination with other chemical-molecular agents may have extraordinary efficacy. This paper will discuss links between mTOR signaling and PCOS and OC, and explore the mechanisms of mTOR inhibitors in treating these two diseases, with conclusions regarding the most effective therapeutic approaches.     

Two hits are better than one: targeting both phosphatidylinositol 3-kinase and mammalian target of rapamycin as a therapeutic strategy for acute leukemia treatment

Phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) are two key components of the PI3K/Akt/mTOR signaling pathway. This signal transduction cascade regulates a wide range of physiological cell processes, that include differentiation, proliferation, apoptosis, autophagy, metabolism, motility, and exocytosis. However, constitutively active PI3K/Akt/mTOR signaling characterizes many types of tumors where it negatively influences response to therapeutic treatments. Hence, targeting PI3K/Akt/mTOR signaling with small molecule inhibitors may improve cancer patient outcome. The PI3K/Akt/mTOR signaling cascade is overactive in acute leukemias, where it correlates with enhanced drug-resistance and poor prognosis. The catalytic sites of PI3K and mTOR share a high degree of sequence homology. This feature has allowed the synthesis of ATP-competitive compounds targeting the catalytic site of both kinases. In preclinical models, dual PI3K/mTOR inhibitors displayed a much stronger cytotoxicity against acute leukemia cells than either PI3K inhibitors or allosteric mTOR inhibitors, such as rapamycin. At variance with rapamycin, dual PI3K/mTOR inhibitors targeted both mTOR complex 1 and mTOR complex 2, and inhibited the rapamycin-resistant phosphorylation of eukaryotic initiation factor 4E-binding protein 1, resulting in a marked inhibition of oncogenic protein translation. Therefore, they strongly reduced cell proliferation and induced an important apoptotic response. Here, we reviewed the evidence documenting that dual PI3K/mTOR inhibitors may represent a promising option for future targeted therapies of acute leukemia patients.     

The phosphatidylinositol 3-kinase/Akt/mTOR signaling network as a therapeutic target in acute myelogenous leukemia patients

The phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling axis plays a central role in cell proliferation, growth, and survival under physiological conditions. However, aberrant PI3K/Akt/mTOR signaling has been implicated in many human cancers, including acute myelogenous leukemia (AML). Therefore, the PI3K/Akt/mTOR network is considered as a validated target for innovative cancer therapy. The limit of acceptable toxicity for standard polychemotherapy has been reached in AML. Novel therapeutic strategies are therefore needed. This review highlights how the PI3K/Akt/mTOR signaling axis is constitutively active in AML patients, where it affects survival, proliferation, and drug-resistance of leukemic cells including leukemic stem cells. Effective targeting of this pathway with small molecule kinase inhibitors, employed alone or in combination with other drugs, could result in the suppression of leukemic cell growth. Furthermore, targeting the PI3K/Akt/mTOR signaling network with small pharmacological inhibitors, employed either alone or in combinations with other drugs, may result in less toxic and more efficacious treatment of AML patients. Efforts to exploit pharmacological inhibitors of the PI3K/Akt/mTOR cascade which show efficacy and safety in the clinical setting are now underway.     

Biologic rationale and clinical activity of mTOR inhibitors in gynecological cancer

Advanced recurrent gynecological malignancies have a poor prognosis despite systemic treatment, which is usually cytotoxic chemotherapy. Responses are generally short-lived and more effective treatments are needed. Rationally designed molecularly targeted therapy is an emerging and important option in this setting. The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase of the phosphatidylinositol-3-kinase (PI3K)/AKT signaling pathway with a critical role in controlling cancer cellular growth, metabolism and cell cycle progression. Aberrant PI3K-dependent signaling occurs frequently in a wide range of tumor types, including ovarian, endometrial and cervical cancer. Early clinical studies of first-generation mTOR inhibitors have shown promising clinical activity in endometrial cancer. However, the molecular basis of sensitivity and resistance to these agents remains largely unknown. In this review, we will update the clinical and biological data underlying the development of first generation mTOR inhibitors in the treatment of gynecological tumors. The role of potential new combination regimens with mTOR inhibitors in gynecological cancers will also be discussed.     

PI3K/Akt/mTOR signaling pathway in cancer stem cells: from basic research to clinical application

Cancer stem cells (CSCs) are a subpopulation of tumor cells that possess unique self-renewal activity and mediate tumor initiation and propagation. The PI3K/Akt/mTOR signaling pathway can be considered as a master regulator for cancer. More and more recent studies have shown the links between PI3K/Akt/mTOR signaling pathway and CSC biology. Herein, we provide a comprehensive review on the role of signaling components upstream and downstream of PI3K/Akt/mTOR signaling in CSC. In addition, we also summarize various classes of small molecule inhibitors of PI3K/Akt/mTOR signaling pathway and their clinical potential in CSC. Overall, the current available data suggest that the PI3K/Akt/mTOR signaling pathway could be a promising target for development of CSC-target drugs.     

Targeting the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway: An emerging treatment strategy for squamous cell lung carcinoma

Squamous cell lung carcinoma accounts for approximately 30% of all non-small cell lung cancers (NSCLCs). Despite progress in the understanding of the biology of cancer, cytotoxic chemotherapy remains the standard of care for patients with squamous cell lung carcinoma, but the prognosis is generally poor. The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway is one of the most commonly activated signaling pathways in cancer, leading to cell proliferation, survival, and differentiation. It has therefore become a major focus of clinical research. Various alterations in the PI3K/AKT/mTOR pathway have been identified in squamous cell lung carcinoma and a number of agents targeting these alterations are in clinical development for use as single agents and in combination with other targeted and conventional treatments. These include pan-PI3K inhibitors, isoform-specific PI3K inhibitors, AKT inhibitors, mTOR inhibitors, and dual PI3K/mTOR inhibitors. These agents have demonstrated antitumor activity in preclinical models of NSCLC and preliminary clinical evidence is also available for some agents. This review will discuss the role of the PI3K/AKT/mTOR pathway in cancer and how the discovery of genetic alterations in this pathway in patients with squamous cell lung carcinoma can inform the development of targeted therapies for this disease. An overview of ongoing clinical trials investigating PI3K/AKT/mTOR pathway inhibitors in squamous cell lung carcinoma will also be included.