EPHA2通过增强Akt/mTOR信号通路促进SGC-7901细胞的增殖

背景与目的：EPHA2能够促进胃癌细胞中Cyclin D1的表达及胃癌细胞的细胞周期进程,从而增强胃癌细胞的增殖能力,但EPHA2调控胃癌细胞中Cyclin D1的表达及胃癌细胞的细胞周期进程的分子机制依然不明确。Akt/mTOR信号通路能够通过促进胃癌细胞中Cyclin D1的表达及胃癌细胞的细胞周期进程增强胃癌细胞的增殖能力,且有研究表明EPHA2能够激活Akt/mTOR信号通路。基于此,该研究探讨了Akt/mTOR信号通路在EPHA2促胃癌细胞增殖中的作用。方法：采用蛋白[质]印迹法(Western blot)检测过表达EPHA2和敲低EPHA2表达对SGC-7901细胞中Akt、mTOR和4EBP1磷酸化的影响。使用Akt抑制剂MK2206和mTOR抑制剂RAD001分别处理转染空载体病毒的SGC-7901-NC细胞和过表达EPHA2的SGC-7901-EPHA2细胞,分别通过CCK8、流式细胞术和Western blot检测细胞增殖、细胞周期及周期相关蛋白Cyclin D1的表达。结果：过表达EPHA2增强SGC-7901细胞中Akt、mTOR和4EBP1的磷酸化,敲低EPHA2的表达抑制SGC-7901细胞中Akt、mTOR和4EBP1的磷酸化。MK2206和RAD001处理细胞时,EPHA2过表达对SGC-7901细胞增殖、细胞S期和Cyclin D1表达的促进作用被显著抑制。结论：EPHA2通过增强Akt/mTOR信号通路促进胃癌细胞SGC-7901的增殖能力,提示我们将来针对EPHA2高表达的胃癌患者或许可以采用Akt抑制剂和mTOR抑制剂予以个体化治疗。     

PTEN对K562细胞mTOR调控的研究

目的:探讨肿瘤抑制基因PTEN在人慢性粒细胞白血病细胞株K562中对哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin ,mTOR)的调控作用,以及雷帕霉素(rapamycin,RAPA)对K562细胞增殖抑制的影响.方法:通过实时荧光定量PCR(real-time fluorescent quantification PCR,RFQ-PCR)法检测甲磺酸伊马替尼(imatinib mexylate)干预K562细胞后BCR/ABL、PTEN、mTOR mRNA的表达水平及相互关系;Western 印迹法检测甲磺酸伊马替尼干预和以腺病毒为载体感染野生型PTEN(Ad-PTEN-GFP )后K562细胞PTEN、Akt和p-Akt的蛋白表达水平;用MTT和FCM方法检测RAPA对不同腺病毒感染组K562细胞增殖及凋亡的影响.结果:格列卫干预K562细胞后,BCR/ABL和mTOR mRNA表达下调,PTEN mRNA表达上调;与感染Ad-GFP组相比,感染Ad-PTEN-GFP组的mTOR mRNA表达下调;Ad-PTEN-GFP感染与10 nmol/L RAPA联合作用于K562细胞能够发挥协同作用,对K562细胞的增殖抑制率明显高于单独作用组.结论:PTEN是mTOR的上游调控基因,能够抑制mTOR的表达.RAPA与野生型PTEN一起可以协同抑制K562细胞的增殖.     

mTOR作为抗癌靶点在泌尿系统肿瘤治疗中的研究进展

哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)能调节蛋白合成,细胞生长和凋亡.针对雷帕霉素抗肿瘤机制的研究表明,很多实质性肿瘤细胞中mTOR均高表达,包括泌尿系统肿瘤,如前列腺癌,膀胱癌和肾癌.前列腺癌和膀胱癌的体外、体内实验证实了mTOR信号通路在调控肿瘤侵袭和转移中的重要性.雷帕霉素及其类似物西罗莫司(temsirolimus,CCI2779)和依维莫司(everolimus,RAD001)都有明确的抗肿瘤作用.治疗前列腺癌和膀胱癌的研究已经进入临床试验阶段.在肾癌的研究中,temsirolimus已经进入临床Ⅱ及Ⅲ阶段.本文针对mTOR作为抗癌靶点在泌尿系统肿瘤治疗中的研究进展作一综述.     

银杏内酯B通过阻抑PI3K/Akt/mTOR信号通路抑制胃癌HGC-27 细胞的恶性生物学行为

目的：探讨银杏内酯B（GKB）是否通过阻抑PI3K/Akt/mTOR信号通路抑制胃癌HGC-27细胞的增殖、凋亡、迁移及侵袭。方法：将HGC-27细胞分为对照、GKB低剂量（100 mg/L）、GKB高剂量（200 mg/L）、GKB高剂量（200 mg/L）+740Y-P（PI3K激活剂）、Ly294002（PI3K抑制剂）组。采用MTT、Edu、FCM、Transwell实验分别检测各组细胞的增殖、凋亡、迁移和侵袭能力,qPCR和WB法分别检测各组细胞中PI3K mRNA、Akt mRNA、mTOR mRNA和Ki-67、caspase-3、p-PI3K/PI3K、p-Akt/Akt、p-mTOR/mTOR蛋白的表达。构建胃癌HGC-27细胞裸鼠移植瘤模型,观察GKB对移植瘤生长的影响,WB法检测移植瘤组织中Ki-67、caspase-3、p-PI3K/PI3K、p-Akt/Akt、p-mTOR/mTOR蛋白的表达。结果：体外实验结果表明,与对照组相比,GKB低剂量组、GKB高剂量组、Ly294002组HGC-27细胞的增殖活力及细胞增殖率、迁移和侵袭细胞数,PI3K、Akt、mTOR mRNA表达,以及Ki-67、p-PI3K/PI3K、p-Akt/Akt、p-mTOR/mTOR蛋白表达均显著降低（均P<0.05）;细胞凋亡率、caspase-3蛋白表达均显著升高（均P<0.05）;740Y-P可部分逆转GKB对HGC-27细胞的抑制作用（均P<0.05）。荷瘤裸鼠实验结果显示,GKB可显著抑制HGC-27细胞裸鼠移植瘤的生长（P<0.05）,且可下调PI3K/Akt/mTOR通路相关蛋白的表达。结论：GKB可通过阻抑PI3K/Akt/mTOR信号通路而抑制胃癌HGC-27细胞增殖、迁移与侵袭并促进其凋亡。     

Akt抑制剂MK-2206在缺氧环境下对结肠癌SW480细胞增殖、侵袭的影响

目的:探讨Akt抑制剂MK-2206在缺氧环境下对人结肠癌SW480细胞增殖、侵袭的影响。方法:根据CCK-8实验结果选择CoCl2和MK-2206的浓度,最后分成空白组、MK-2206组、CoCl2组、MK-2206+CoCl2组;Transwell小室实验检测四组细胞的迁移和侵袭能力;RT-PCR法检测各细胞组中Akt、mTOR、HIF-1α的mRNA表达水平;Western blot技术检测各细胞组中Akt、p-Akt、mTOR、p-mTOR、HIF-1α蛋白表达的差异性情况。结果:CoCl2诱导的缺氧环境可以促进SW480细胞的侵袭、迁移(P＜0.05),同时能够促进HIF-1α的mRNA和蛋白表达(P＜0.05),但是低浓度范围内的CoCl2对SW480细胞增殖活性无明显影响(P＞0.05);MK-2206可以在体外的常氧和缺氧环境中抑制SW480细胞的增殖活性和侵袭、迁移能力(P＜0.05);MK-2206能在体外的常氧环境下抑制SW480细胞的Akt、mTOR、HIF-1α的mRNA表达(P＜0.05),缺氧环境无明显作用;同时MK-2206能够在常氧和缺氧环境中显著降低p-Akt、p-mTOR、HIF-1α的蛋白表达水平(P＜0.05)。 结论:Akt抑制剂MK-2206可以在体外的常氧和缺氧环境下抑制SW480细胞的增殖活性和侵袭能力,但缺氧环境可能会弱化MK-2206对SW480细胞迁移的抑制作用。     

CerS2对膀胱癌细胞增殖、迁移及AKT/mTOR信号通路的影响

目的:探究CerS2基因在膀胱癌细胞中的作用及其可能的机制。方法:构建pEGFP-C1-CerS2重组表达载体,并转染膀胱癌细胞系T24,使用蛋白质免疫印迹实验检测GFP-CerS2的表达;运用CCK-8法检测细胞增殖活性;运用Annexin Ｖ荧光标记实验检测细胞凋亡水平;分别使用细胞划痕实验及Transwell实验检测细胞迁移能力和侵袭能力;使用蛋白质免疫印迹实验检测细胞中AKT、p-AKT、mTOR及p-mTOR的表达水平。结果:重组GFP-CerS2融合蛋白在T24细胞中可以正常表达,过表达GFP-CerS2显著抑制了膀胱癌细胞的增殖活性,且显著增加了细胞凋亡水平。过表达GFP-CerS2抑制了膀胱癌细胞的迁移和侵袭能力。此外,过表达GFP-CerS2也显著抑制了膀胱癌细胞中AKT和mTOR的磷酸化修饰,但不影响总AKT及mTOR的表达水平。结论:过表达CerS2可以抑制AKT/mTOR信号通路,影响膀胱癌细胞的增殖和凋亡,并抑制细胞的迁移和侵袭能力。     

miR-26a抑制ST3GAL6基因介导mTOR信号通路对小鼠Lewis肺癌细胞增殖凋亡的作用机制

目的:探究miR-26a靶向调控ST3GAL6基因介导mTOR信号通路对小鼠Lewis肺癌细胞增殖凋亡的作用机制。方法:构建肺癌小鼠模型,将小鼠分为正常组和模型组;免疫组化检测ST3GAL6在肺组织中的表达情况,qRT-PCR法检测miR-26a在组织中的表达;细胞分为空白组、阴性对照组、miR-26a mimic组、miR-26a inhibitor组、si-ST3GAL6组、miR-26a inhibitor+si-ST3GAL6组和miR-26a mimic+RAD001（mTOR抑制剂）组;qRT-PCR法检测细胞中miR-26a和ST3GAL6 mRNA的表达情况;MTT法和流式细胞术分别检测各组细胞的增殖和凋亡情况;Western blot法测定各组细胞ST3GAL6、p-mTOR、Akt蛋白相对表达量。结果:miR-26a和ST3GAL6在肺癌小鼠肺癌组织中均高表达（均P<0.05）。与空白组相比,miR-26a mimic组ST3GAL6 mRNA及蛋白表达上升,Akt、p-mTOR蛋白表达上升,细胞增殖率上升、凋亡率下降（均P<0.05）;而miR-26a inhibitor组、si-ST3GAL6组和miR-26a inhibitor+si-ST3GAL6组ST3GAL6 mRNA及蛋白表达下调,Akt、p-mTOR蛋白表达下降,细胞增殖率下降、凋亡率上升（均P<0.05）。同时,miR-26a表达在miR-26a mimic组和miR-26a mimic+RAD001组中上升,miR-26a inhibitor组和miR-26a inhibitor+si-ST3GAL6组中下降（均P<0.05）。结论:miR-26a下调ST3GAL6基因,抑制mTOR信号通路活化,抑制肺癌细胞增殖及促进细胞的凋亡。     

PI3K/AKT/MTOR信号通路对肾癌A498细胞增殖、迁移及侵袭的影响研究

目的 探讨PI3K/AKT/MTOR信号通路对肾癌A498细胞增殖、迁移及侵袭的影响.方法 选用PI3K/MTOR双重阻断剂NVP-BEZ235体外处理肾癌A498细胞,浓度分别为0、100、250、500 nmol/L.48 h后采用蛋白质印迹法(Western blot)检测肾癌A498细胞中AKT和MTOR蛋白磷酸化情况;MTT法检测细胞增殖情况;细胞划痕实验检测细胞迁移能力;Transwell小室检测细胞侵袭能力;Western blot法检测细胞中E-Cadherin和PTEN蛋白表达变化.结果 肾癌A498细胞中p-AKT、MTOR、p-MTOR、E-Cadherin、PTEN的表达及细胞增殖率、迁移率、穿膜细胞数量各自在不同NVP-BEZ235浓度下比较,差异均有统计学意义(P﹤0.01).与0 nmol/L组比较,100、250、500 nmol/L的NVP-BEZ235处理肾癌A498细胞后,细胞中磷酸化蛋白p-AKT和p-MTOR的表达均下调,细胞增殖率下降,细胞迁移率下降,穿膜细胞数量减少,细胞中E-Cadherin和PTEN蛋白表达均上调,差异均有统计学意义(P﹤0.05).结论 通过阻断PI3K/AKT/MTOR信号通路可以抑制肾癌A498细胞的增殖、迁移和侵袭,可能与上调细胞中E-Cadherin和PTEN蛋白表达有关.     

布洛芬通过PI3K/Akt/mTOR信号通路调控肝癌QGY-7703细胞迁移和侵袭的机制

目的 探讨布洛芬通过PI3K/Akt/mTOR信号通路对肝癌QGY-7703细胞迁移和侵袭的调控机制。方法 取对数生长期人肝癌细胞QGY-7703,采用随机法分为两组,对照组（C组）：加入等容量的RPMI l640培养液;实验组（B组）：按照不同布洛芬浓度分为三个亚组：B1组250 μmol/L,B2组500 μmol/L、B3组1 000 μmol/L。各组分别作用24、48和72 h后,利用Transwell小室检测各组细胞的侵袭和迁移能力。各组分别作用48 h后,采用Real-time PCR检测各组细胞中PI3K、PTEN和MMP-9基因表达的变化;用Western blot检测各组细胞中PTEN、Akt、磷酸化Akt（p-Akt）、mTOR、磷酸化mTOR（p-mTOR）和MMP-9蛋白表达情况。结果 与C组比较,B1、B2、B3三组细胞迁移和侵袭能力均降低,具有浓度和时间的依赖性,差异有统计学意义（P<0.01）;与C组比较,B1、B2、B3三组细胞PTEN mRNA和PTEN蛋白表达明显升高,且随着布洛芬作用浓度的增加而升高,具有浓度依赖性,差异有统计学意义（P<0.05）;与C组比较,B1、B2、B3三组细胞PI3K mRNA、Akt和mTOR蛋白的表达量差异均无统计学意义（P>0.05）;与C组比较,B1、B2、B3三组细胞MMP-9 mRNA和蛋白的表达以及p-Akt、p-mTOR蛋白的表达均显著下降,且随着布洛芬作用浓度的增加而降低,具有良好的浓度依赖性,差异有统计学意义（P<0.05）。结论 布洛芬可以抑制QGY-7703细胞的迁移和侵袭能力,与布洛芬对细胞PI3K/Akt/mTOR信号通路的调控有关。     

依维莫司对前列腺癌PC-3细胞的抑制和凋亡的影响

摘 要：［目的］ 探讨依维莫司对前列腺癌PC-3细胞凋亡及caspase-3表达的影响。［方法］ 体外培养前列腺癌细胞PC-3,使用不同浓度依维莫司(0mol/L、10-9mol/L和10-8mol/L)干预细胞,四氮唑蓝比色法(MTT)和原位细胞凋亡检测法(TUNEL)检测依维莫司对前列腺癌细胞PC-3生长抑制和诱导细胞凋亡的作用,流式细胞术检测其对caspase-3活化的情况。［结果］ 与对照组比较,依维莫司对前列腺癌PC-3细胞抑制和诱导凋亡作用明显(P<0.05),明显增加caspase-3的表达(P<0.05)。［结论］ 依维莫司抑制前列腺癌细胞PC-3增殖,可能通过诱导caspase-3表达活化增强,最终导致细胞凋亡。     

Inhibition of mTOR pathway by everolimus cooperates with EGFR inhibitors in human tumours sensitive and resistant to anti-EGFR drugs

Inhibition of a single transduction pathway is often inefficient due to activation of alternative signalling. The mammalian target of rapamycin (mTOR) is a key intracellular kinase integrating proliferation, survival and angiogenic pathways and has been implicated in the resistance to EGFR inhibitors. Thus, mTOR blockade is pursued to interfere at multiple levels with tumour growth. We used everolimus (RAD001) to inhibit mTOR, alone or in combination with anti-EGFR drugs gefitinib or cetuximab, on human cancer cell lines sensitive and resistant to EGFR inhibitors, both in vitro and in vivo. We demonstrated that everolimus is active against EGFR-resistant cancer cell lines and partially restores the ability of EGFR inhibitors to inhibit growth and survival. Everolimus reduces the expression of EGFR-related signalling effectors and VEGF production, inhibiting proliferation and capillary tube formation of endothelial cells, both alone and in combination with gefitinib. Finally, combination of everolimus and gefitinib inhibits growth of GEO and GEO-GR (gefitinib resistant) colon cancer xenografts, activation of signalling proteins and VEGF secretion. Targeting mTOR pathway with everolimus overcomes resistance to EGFR inhibitors and produces a cooperative effect with EGFR inhibitors, providing a valid therapeutic strategy to be tested in a clinical setting.     

The mTOR pathway inhibitor RAD001 (everolimus) is highly efficacious in tamoxifen-sensitive and -resistant breast cancer xenografts

The rapamycin derivative RAD001 (everolimus) is presently in clinical trials. Preclinical studies have suggested preferential activity in antiestrogen resistant breast cancer cells. We investigated the response of breast cancer xenografts with different tamoxifen (TAM) sensitivity towards RAD001 and analyzed the regulatory machinery as well as the cross-talk between different signaling pathways. The ERα-positive and TAM-sensitive patient-derived breast carcinoma model 3366, its TAM-resistant counterpart 3366/TAM and 4049, a breast cancer with inherent TAM-resistance, were transplanted to immunodeficient nude mice and treated with RAD001 or TAM or the combination of both compounds. Shock frozen tumors were prepared for Western Blot and immunohistochemical analysis to semi-quantitatively evaluate the expression of the ERα and the ERα regulated IGF-IR as well as PTEN, pAkt, mTOR, (phospho)-p70^S6K, (phospho)-4E-BP1 and cyclin D1. RAD001 significantly inhibited the growth of tamoxifen responding and non-responding xenografts. The highest efficacy was found for the combined treatment with TAM and RAD001. RAD001 modified the protein expression of mTOR and its downstream molecule 4E-BP1 as well as the level of PTEN and ERα, but independent of the tumors sensitivity towards TAM. The protein kinase Akt was found in the active phosphorylated form (pAkt) only in TAM-resistant xenografts, but not detectable in the TAM-responding 3366 line. All treatment modalities down-regulated pAkt expression in the TAM-resistant tumors. p70^S6K and IGF-IR proteins were not significantly influenced by RAD001 treatment. Our findings document the linkage between different growth-controlling pathways. Due to its capability to be active in a TAM-resistant in vivo model, RAD001 could potentially serve as a promising second-line therapy in breast cancer.     

Dual inhibition of mTOR and estrogen receptor signaling in vitro induces cell death in models of breast cancer.

PURPOSE: RAD001 (everolimus), a mammalian target of rapamycin (mTOR) pathway inhibitor in phase II clinical trials in oncology, exerts potent antiproliferative/antitumor activities. Many breast cancers are dependent for proliferation on estrogens synthesized from androgens (i.e., androstenedione) by aromatase. Letrozole (Femara) is an aromatase inhibitor used for treatment of postmenopausal women with hormone-dependent breast cancers. The role of the mTOR pathway in estrogen-driven proliferation and effects of combining RAD001 and letrozole were examined in vitro in two breast cancer models. EXPERIMENTAL DESIGN: The role of the mTOR pathway in estrogen response was evaluated in aromatase-expressing MCF7/Aro breast cancer cells by immunoblotting. Effects of RAD001 and letrozole (alone and in combination) on the proliferation and survival of MCF7/Aro and T47D/Aro cells were evaluated using proliferation assays, flow cytometry, immunoblotting, and apoptosis analyses. RESULTS: Treatment of MCF7/Aro cells with estradiol or androstenedione caused modulation of the mTOR pathway, a phenomenon reversed by letrozole or RAD001. In MCF7/Aro and T47D/Aro cells, both agents inhibited androstenedione-induced proliferation; however, in combination, this was significantly augmented (P < 0.001, two-way ANOVA, synergy by isobologram analysis). Increased activity of the combination correlated with more profound effects on G1 progression and a significant decrease in cell viability (P < 0.01, two-way ANOVA) defined as apoptosis (P < 0.05, Friedman test). Increased cell death was particularly evident with optimal drug concentrations. CONCLUSION: mTOR signaling is required for estrogen-induced breast tumor cell proliferation. Moreover, RAD001-letrozole combinations can act in a synergistic manner to inhibit proliferation and trigger apoptotic cell death. This combination holds promise for the treatment of hormone-dependent breast cancers.     

人参皂苷Rh2通过Egr-1/TRL4/mTOR信号通路抑制食管癌细胞Eca-109增殖、迁移和EMT

目的:研究人参皂苷Rh2对食管癌细胞Eca-109增殖、迁移和上皮间质转化（epithelial-mesenchymal transition,EMT）的作用以及作用机制。方法:CCK-8法检测人参皂苷Rh2对食管癌细胞Eca-109增殖的影响;细胞划痕实验检测人参皂苷Rh2对食管癌Eca-109细胞迁移的影响;Western blot检测EMT相关蛋白E-cadherin、Vimentin和Slug的蛋白表达水平。结果:人参皂苷Rh2能够显著抑制Eca-109细胞的增殖,且呈剂量依赖性;此外,人参皂苷Rh2显著抑制E-cadherin、Vimentin和Slug的蛋白表达,并抑制Eca-109细胞迁移;人参皂苷Rh2显著抑制Egr-1、TRL4和mTOR的蛋白表达;进一步的研究结果表明人参皂苷Rh2通过抑制Egr-1/TRL4/mTOR信号通路抑制食管癌细胞Eca-109增殖、迁移和EMT。结论:人参皂苷Rh2能够抑制食管癌细胞Eca-109的增殖、迁移和EMT,其作用机制是通过介导Egr-1/TRL4/mTOR信号通路来实现的。这一结果能够为治疗食管癌的进一步研究提供分子基础。     

PTEN loss does not predict for response to RAD001 (Everolimus) in a glioblastoma orthotopic xenograft test panel.

PURPOSE: Hyperactivation of the phosphatidylinositol 3-kinase/Akt signaling through disruption of PTEN function is common in glioblastoma multiforme, and these genetic changes are predicted to enhance sensitivity to mammalian target of rapamycin (mTOR) inhibitors such as RAD001 (everolimus). EXPERIMENTAL DESIGN: To test whether PTEN loss could be used as a predictive marker for mTOR inhibitor sensitivity, the response of 17 serially transplantable glioblastoma multiforme xenografts was evaluated in an orthotopic therapy evaluation model. Of these 17 xenograft lines, 7 have either genomic deletion or mutation of PTEN. RESULTS: Consistent with activation of Akt signaling, there was a good correlation between loss of PTEN function and elevated levels of Akt phosphorylation. However, of the 7 lines with disrupted PTEN function, only 1 tumor line (GBM10) was significantly sensitive to RAD001 therapy (25% prolongation in median survival), whereas 1 of 10 xenograft lines with wild-type PTEN was significantly sensitive to RAD001 (GS22; 34% prolongation in survival). Relative to placebo, 5 days of RAD001 treatment was associated with a marked 66% reduction in the MIB1 proliferation index in the sensitive GBM10 line (deleted PTEN) compared with a 25% and 7% reduction in MIB1 labeling index in the insensitive GBM14 (mutant PTEN) and GBM15 (wild-type PTEN) lines, respectively. Consistent with a cytostatic antitumor effect, bioluminescent imaging of luciferase-transduced intracranial GBM10 xenografts showed slowed tumor growth without significant tumor regression during RAD001 therapy. CONCLUSION: These data suggest that loss of PTEN function is insufficient to adequately predict responsiveness to mTOR inhibitors in glioblastoma multiforme.     

PTEN deficiency is associated with reduced sensitivity to mTOR inhibitor in human bladder cancer through the unhampered feedback loop driving PI3K/Akt activation

Background:

Preclinical studies have shown that PTEN loss enhances sensitivity to mammalian target of Rapamycin (mTOR) inhibitors because of facilitated PI3K (phosphatidylinositol-3 kinase)/Akt activation and consecutive stimulation of the mTOR pathway. In patients with advanced transitional cell carcinoma (TCC) treated with the mTOR inhibitor everolimus, PTEN loss was, however, associated with resistance to treatment.

Methods:

Transitional cell carcinoma specimens, human bladder cancer cells and derived mouse xenografts were used to evaluate how the PTEN status influences the activity of mTOR inhibitors.

Results:

Transitional cell carcinoma patients with a shorter progression-free survival under everolimus exhibited PTEN deficiency and increased Akt activation. Moreover, PTEN-deficient bladder cancer cells were less sensitive to rapamycin than cells expressing wild-type PTEN, and rapamycin strikingly induced Akt activation in the absence of functional PTEN. Inhibition of Akt activation by the PI3K inhibitor wortmannin interrupted this rapamycin-induced feedback loop, thereby enhancing the antiproliferative effects of the mTOR inhibitor both in vitro and in vivo.

Conclusion:

Facilitation of Akt activation upon PTEN loss can have a more prominent role in driving the feedback loop in response to mTOR inhibition than in promoting the mTOR pathway. These data support the use of both PI3K and mTOR inhibitors to treat urothelial carcinoma, in particular in the absence of functional PTEN.