MAG - 1 和 mTOR 生物学功能研究进展

PI3K/Akt/mTOR信号传导通路是细胞内重要的信号传导通路之一,mTOR是该通路的焦点,其上游和下游效应分子的不同活化状态对细胞的增殖、运动等生物学功能发挥重要作用.MAG-1是近年来新发现的mTOR上游效应分子,通过mTOR信号传导通路发挥生物学功能.本文就MAG-1和mTOR生物学功能研究进展作一综述.     

mTOR功能及其抑制剂研究进展

哺乳动物雷帕霉素靶蛋白（mammalian target of rapamycin mTOR）是一种丝／苏氨酸蛋白激酶，mTOR在肿瘤细胞生长、增殖过程中起重要作用，mTOR信号通路活动异常与肿瘤的发生有密切关系，mTOR足肿瘤药物治疗作用的理想靶点，目前新的mTOR抑制剂不断出现。本文对mTOR蛋白的结构、功能和mTOR信号通路及其抑制剂进行了综述。     

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。     

mTOR的反馈激活机制及其抑制剂的抗肿瘤应用

mTOR是处于调节细胞代谢、生长、增殖等整个过程中心环节的重要激酶。干扰或抑制mTOR会引起细胞尤其是癌细胞的生长停滞继而死亡,因而也被公认为是癌症治疗当中的一个潜在靶标。一系列的mTOR抑制剂Rapamycin及类似物已经形成并在临床抗肿瘤中有所应用,但其展示的效应非常有限。随着研究的深入,发现mTOR信号通路存在反馈激活机制:即抑制mTOR能反馈性激活多个与细胞生长增殖相关的信号通路。并且认为是这些反馈激活机制削弱了mTOR抑制剂的效能,也是其临床效应未达预期的原因。本文就目前国内外研究较深入的mTOR-AKT,mTOR-ERK,mTOR-eIF4E反馈信号通路做详细概述,并阐述目前采取的防止这一反馈机制形成的Rapamycin类似物与特定通路抑制剂的联合用药策略,使mTOR抑制剂在临床抗肿瘤中能充分发挥其效能。      

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。     

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。      

PI3K/Akt/mTOR信号通路抑制剂在乳腺癌中的研究进展

目的:总结PI3K/Akt/mTOR信号通路靶向治疗在乳腺癌中的研究进展.方法:以“PI3K/Akt/mTOR、信号通路和乳腺癌”等为关键词,检索2000-01-2011-06 PubMed、Ovid和Springer等数据库的相关文献.纳入标准:1)关于PI3K/Akt/mTOR信号通路的组成、功能特点;2)PI3K/Akt/mTOR信号通路与乳腺癌的关系研究;3)以PI3K/Akt/mTOR信号通路中关键分子为靶点的乳腺癌治疗.根据纳入标准,符合分析的文献40篇.结果:信号转导通路的异常是肿瘤发生、发展的重要步骤,PI3K/Akt/mTOR信号通路与人类多种肿瘤密切相关,其在肿瘤细胞的增殖、存活、抵抗凋亡、血管发生和转移以及对放化疗抵抗中发挥了重要作用.乳腺癌中常见PI3K/Akt/mTOR信号通路的异常激活,以此通路为靶点的药物已成为乳腺癌治疗的研究热点.结论:靶向PI3K/Akt/mTOR通路中关键分子的众多药物在乳腺癌开展了一系列相关的临床试验研究,一部分显示出较好的安全性和有效性.随着对PI3K/Akt/mTOR通路的分子生物学机制的深入研究,期待靶向此通路的抑制剂将会在乳腺癌治疗中发挥巨大的作用,进一步提高乳腺癌患者的疗效和改善预后.     

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抑制剂在激素受体阳性乳腺癌治疗中的研究进展

靶向激素受体（hormone receptor,HR）和人类表皮生长因子（human epidermal growth factor receptor 2,HER-2）对激素受体阳性乳腺癌的治疗至关重要,然而原发或继发内分泌治疗耐药及后续的疾病进展仍不可避免。人哺乳动物雷帕霉素位点（mammalian target of rapamycin,mTOR）是细胞生长和分化的关键调节因子,参与细胞不可控性生长。目前许多研究表明mTOR通路的激活可能与乳腺癌内分泌治疗耐药相关,阻断此通路有助于消除耐药,维持药物的敏感性。许多靶向mTOR通路的药物均表现出强大的抗肿瘤效应,在乳腺癌治疗中具有良好前景,且已有许多临床试验结果表明mTOR抑制剂联合内分泌治疗可显著提高患者的生存率。本文对mTOR信号通路及其抑制剂在内分泌治疗耐药的乳腺癌中的新进展进行综述。      

PI3K抑制剂在乳腺癌治疗中的应用现状

PI3K/Akt/mTOR信号通路是细胞内的重要信号通路,在调节肿瘤细胞的增殖、分化、转移过程中发挥重要作用.该信号通路的激活与多种肿瘤的发生和发展有密切关系.随着近些年对分子生物学的深入研究发现,磷脂酰肌醇3-激酶(PI3K)通路的异常激活在乳腺癌中最为常见,也使得该通路成为乳腺癌新的治疗靶点,现已研发出多种作用于P...     

A dual-targeted molecular therapy of PP242 and cetuximab plays an anti-tumor effect through EGFR downstream signaling pathways in colorectal cancer

BackgroundEpidermal growth factor receptor (EGFR) and its downstream Ras-mitogen-activated protein kinase kinase (MAPKK, MEK)-extracellular regulated protein kinase (ERK) signaling pathway and phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling pathway play important roles in the pathogenesis of colorectal cancer (CRC). The combination therapy of anti-EGFR and anti-mTOR needs to be explored.MethodsHere we combined the anti-EGFR monoclonal antibody cetuximab (CTX) with the mTOR inhibitor PP242 in CRC cell lines and mouse xenograft models and discussed the changes of EGFR downstream signaling pathways of CRC cell lines.ResultsIn HT-29 cells and Caco-2 cells, combined application of CTX and PP242 significantly inhibited the proliferation of CRC cells in vivo and in vitro. In BRAF wild-type Caco-2 cells, combined application of CTX and PP242 inhibited the activation of the EGFR and its downstream signaling pathways.ConclusionsOur research further demonstrates the effectiveness of the combined application of CTX and PP242 in inhibiting CRC cell lines from the perspective of cell proliferation, cell cycle, apoptosis, and mouse xenografts. We revealed that the combined application of CTX and PP242 can inhibit tumor growth and proliferation by inhibiting the phosphorylation of key molecules in EGFR downstream MEK-ERK and MEK 4/7 (MKK)-c-Jun N-terminal kinase (JNK) signaling pathways in BRAF wild-type CRC cells. In addition, we found that in BRAF mutant CRC cells, the monotherapy of PP242 resulted in negative feedback increased EGFR phosphorylation rates, accompanied by significant up-regulation of downstream MEK and ERK phosphorylation.     

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.     

Potential Targets for Prevention of Colorectal Cancer: a Focus on PI3K/Akt/mTOR and Wnt Pathways

Colorectal cancer (CRC) is one of the most common cancers in many parts of the world. Its development is a multi-step process involving three distinct stages, initiation that alters the molecular message of a normal cell, followed by promotion and progression that ultimately generates a phenotypically altered transformed malignant cell. Reports have suggested an association of the phosphoinositide-3-kinase (PI3K)/Akt pathway with colon tumorigenesis. Activation of Akt signaling and impaired expression of phosphatase and tensin homolog (PTEN) (a negative regulator of Akt) has been reported in 60-70% of human colon cancers and inhibitors of PI3K/Akt signaling have been suggested as potential therapeutic agents. Around 80% of human colon tumors possess mutations in the APC gene and half of the remainder feature β-catenin gene mutations which affect downstream signaling of the PI3K/Akt pathway. In recent years, there has been a great focus in targeting these signaling pathways, with natural and synthetic drugs reducing the tumor burden in different experiment models. In this review we survey the role of PI3K/Akt/mTOR and Wnt signaling in CRC.     

DEPTOR Expression Negatively Correlates with mTORC1 Activity and Tumor Progression in Colorectal Cancer

The mammalian target of rapamycin (mTOR) signaling pathway is upregulated in the pathogenesis of manycancers, including colorectal cancer (CRC). DEPTOR is an mTOR inhibitor whose expression is negativelyregulated by mTOR. However, the role of DEPTOR in the development of CRC is not known. The aim of thisstudy was to investigate the expression of DEPTOR and mTORC1 activity (P-S6) in a subset of CRC patientsand determine their relation to tumor differentiation, invasion, nodal metastasis and disease-free survival. Here,Immunohistochemical expression of P-S6 (S235/236) and DEPTOR were evaluated in 1.5 mm tumor cores from90 CRC patients and in 90 samples of adjacent normal mucosa by tissue microarray. The expression of P-S6(S235/236) was upregulated in CRC, with the positive rate of P-S6 (S235/236) in CRC (63.3%) significantly higherthan that in control tissues (36.7%, 30%) (p<0.05). P-S6 (S235/236) also correlated with high tumor histologicgrade (p=0.002), and positive nodal metastasis (p=0.002). In contrast, the expression level of DEPTOR wascorrelated with low tumor histological grade (p=0.006), and negative nodal metastasis (p=0.001). Interestingly,P-S6 (S235/236) expression showed a significant negative association with the expression of DEPTOR in CRC(p=0.011, R= -0.279). However, upregulation of P-S6 (S235/236) (p=0.693) and downregulation of DEPTOR(p=0.331) in CRC were not significantly associated with overall survival. Thus, we conclude that expression ofDEPTOR negatively correlates with mTORC1 activity and tumor progression in CRC. DEPTOR is a potentialmarker for prognostic evaluation and a target for the treatment of CRC.     

mTOR和PTEN在非小细胞肺癌组织中的表达及临床意义

背景与目的 mTOR是调节细胞生长和增殖的重要信号转导分子,也是一种蛋白激酶.它通过活化下游的相关的效应蛋白发挥作用.在信号转导通路中PTEN基因可通过对该信号途径的负调控而抑制mTOR的活化.本研究通过分析mTOR信号转导途径中mTOR和PTEN基因在非小细胞肺癌(non-small cell lung cancer,NSCLC)组织中的表达和临床意义.方法 外科手术中获取65例NSCLC组织及30例癌旁组织,RT-PCR技术检测NSCLC组织及癌旁组织中mTOR和PTEN基因的表达水平.结果 mTOR在NSCLC组织中表达量(0.23±0.16)显著高于癌旁组(0.12±0.09)(P<0.01),PTEN在NSCLC组织中表达量(0.19±0.28)显著低于癌旁组(0.53±0.28)(P<0.01).mTOR和PTEN与病人的性别、年龄、病理类型、淋巴结转移情况无关,与病人的肿瘤大小有关.结论 mTOR在NSCLC中被激活,PTEN在NSCLC组织表达缺失或减少,mTOR路的激活和PTEN表达缺失在NSCLC发生发展中起到一定的作用.     

miRNA-99b-5p suppresses liver metastasis of colorectal cancer by down-regulating mTOR

Liver metastasis is common in patients diagnosed with colorectal cancer (CRC), and is also correlated with poor outcome. In this study we screened the different expression profiles of microRNAs (miRNAs) on the development of liver metastasis in CRC patients. miR-99b-5p was found to be more than 6-fold higher in primary tumors than in matched liver metastases (P = 0.007). Expression of miR-99b-5p in primary tumors of patients with stage III CRC without liver metastases was higher than in CRC patients with liver metastases (P = 0.028). Up-regulated miR-99b-5p was associated with longer overall survival (P = 0.01). Besides, miR-99b-5p silencing in miR-99b-5p-positive CRC cell lines promoted cell migration and up-regulated mTOR, and vice versa. In addition, luciferase assays demonstrated that miR-99b-5p functioned as a tumor suppressor by targeting mTOR. Taken together, our results demonstrate thatmiR-99b-5p is differently expressed in primary CRC and liver metastasis and functions as a tumor-suppressive microRNA in metastatic CRC. The miR-99b-5p–mTOR axis may serve as a prognostic factor and therapeutic target for anti-metastatic therapy in CRC patients.     

Chronic mTOR activation promotes cell survival in Merkel cell carcinoma

Merkel cell carcinoma (MCC) is an aggressive skin cancer with rising incidence. In this study, we demonstrate that mTOR activation and suppressed autophagy is common in MCCs. mTOR inhibition in two primary human MCC cell lines induces autophagy and cell death that is independent of caspase activation but can be attenuated by autophagy inhibition. This is the first study to evaluate mTOR and autophagy in MCC. Our data suggests a potential role of autophagic cell death upon mTOR inhibition and thus uncovers a previously underappreciated role of mTOR signaling and cell survival, and merits further studies for potential therapeutic targets.     

Selective targeting of human colon cancer stem-like cells by the mTOR inhibitor Torin-1

Metastatic colorectal cancer (CRC) is incurable for most patients. Since mammalian target of rapamycin (mTOR) has been suggested as a crucial modulator of tumor biology, we aimed at evaluating the effectiveness of mTOR targeting for CRC therapy. To this purpose, we analyzed mTOR expression and the effect of mTOR inhibition in cancer stem-like cells isolated from three human metastatic CRCs (CoCSCs).CoCSCs exhibited a strong mTOR complex 2 (mTORC2) expression, and a rare expression of mTOR complex 1 (mTORC1). This latter correlated with differentiation, being expressed in CoCSC-derived xenografts. We indicate Serum/glucocorticoid-regulated kinase 1 (SGK1) as the possible main mTORC2 effector in CoCSCs, as highlighted by the negative effect on cancer properties following its knockdown. mTOR inhibitors affected CoCSCs differently, resulting in proliferation, autophagy as well as apoptosis induction. The apoptosis-inducing mTOR inhibitor Torin-1 hindered growth, motility, invasion, and survival of CoCSCs in vitro, and suppressed tumor growth in vivo with a concomitant reduction in vessel formation. Torin-1 also affected the expression of markers for cell proliferation, angio-/lympho-genesis, and stemness in vivo, including Ki67, DLL1, DLL4, Notch, Lgr5, and CD44. Importantly, Torin-1 did not affect the survival of normal colon stem cells in vivo, suggesting its selectivity towards cancer cells. Thus, we propose Torin-1 as a powerful drug candidate for metastatic CRC therapy.