2475

MTOR

In cancer progression, carcinoma cells gain invasive behavior through a loss of epithelial characteristics and acquisition of mesenchymal properties, a process that can lead to epithelial-mesenchymal transition (EMT). TGF-beta is a potent inducer of EMT, and increased TGF-beta signaling in cancer cells is thought to drive cancer-associated EMT. Here, we examine the physiological requirement for mTOR complex 2 (mTORC2) in cells undergoing EMT. TGF-beta rapidly induces mTORC2 kinase activity in cells undergoing EMT, and controls epithelial cell progression through EMT. By regulating EMT-associated cytoskeletal changes and gene expression, mTORC2 is required for cell migration and invasion. Furthermore, inactivation of mTORC2 prevents cancer cell dissemination in vivo. Our results suggest that the mTORC2 pathway is an essential downstream branch of TGF-beta signaling, and represents a responsive target to inhibit EMT and prevent cancer cell invasion and metastasis.

epithelial-to-mesenchymal transition (EMT) is a transdifferentiation process that converts epithelial cells into highly motile mesenchymal cells. This physiologic process occurs largely during embryonic development but is aberrantly reactivated in different pathologic situations, including fibrosis and cancer. We conducted a siRNA screening targeted to the human kinome with the aim of discovering new EMT effectors. With this approach, we have identified mTOR complex 1 (mTORC1), a nutrient sensor that controls protein and lipid synthesis, as a key regulator of epithelial integrity. Using a combination of RNAi and pharmacologic approaches, we report here that inhibition of either mTOR or RPTOR triggers EMT in mammary epithelial cells. This EMT was characterized by the induction of the mesenchymal markers such as fibronectin, vimentin, and PAI-1, together with the repression of epithelial markers such as E-cadherin and ZO-3. In addition, mTORC1 blockade enhanced in vivo migratory properties of mammary cells and induced EMT independent of the TGF-beta pathway. Finally, among the transcription factors known to activate EMT, both ZEB1 and ZEB2 were upregulated following mTOR repression. Their increased expression correlated with a marked reduction in miR-200b and miR-200c mRNA levels, two microRNAs known to downregulate ZEB1 and ZEB2 expression. Taken together, our findings unravel a novel function for mTORC1 in maintaining the epithelial phenotype and further indicate that this effect is mediated through the opposite regulation of ZEB1/ZEB2 and miR-200b and miR-200c. Furthermore, these results suggest a plausible etiologic explanation for the progressive pulmonary fibrosis, a frequent adverse condition associated with the therapeutic use of mTOR inhibitors.CI - (c)2013 AACRFAU - Mikaelian, Ivan

Recently, an increasing number of studies have suggested that mTOR plays a critical role in the regulation of tumor cell motility, invasion and cancer metastasis. However, little is known about the signaling mechanisms in regulating epithelial-mesenchymal transition (EMT) of prostate cancer. In this study, we found that the expression levels of Raptor and Rictor in prostate cancer tissues were elevated, which may suggest that Raptor and Rictor signaling pathways are associated with prostate cancer progression and metastasis. Inhibition of mTORC1 or mTORC2 by knock down of Raptor or Rictor, respectively, migration and invasion of prostate cancer were attenuated. Furthermore, EMT, a characterized by the changed expression levels of various markers like E-cadherin, beta-catenin, N-cadherin, and vimentin emergend following inhibition of Raptor or Rictor. Finally, the small GTPases (RhoA and Rac1) which were crucial regulatory proteins in cell migration and invasion were inactivited after downregulating Raptor and Rictor. These results suggest that mTOR regulate EMT at least in part by down regulation of RhoA and Rac1 signaling pathways. Our findings provide novel very attractive target strategies that the inhibition of mTOR signaling pathways may retard prostate cancer migration and invasion at early stages.CI - (c) 2014 Wiley Periodicals, Inc.

Plumbagin (PLB), an active naphthoquinone compound, has shown potent anticancer effects in preclinical studies; however, the effect and underlying mechanism of PLB for the treatment of pancreatic cancer is unclear. This study aimed to examine the pancreatic cancer cell killing effect of PLB and investigate the underlying mechanism in human pancreatic cancer PANC-1 and BxPC-3 cells. The results showed that PLB exhibited potent inducing effects on cell cycle arrest in PANC-1 and BxPC-3 cells via the modulation of cell cycle regulators including CDK1/CDC2, cyclin B1, cyclin D1, p21 Waf1/Cip1, p27 Kip1, and p53. PLB treatment concentration- and time-dependently increased the percentage of autophagic cells and significantly increased the expression level of phosphatase and tensin homolog, beclin 1, and the ratio of LC3-II over LC3-I in both PANC-1 and BxPC-3 cells. PLB induced inhibition of phosphatidylinositol 3-kinase (PI3K)/protein kinase B/mammalian target of rapamycin and p38 mitogen-activated protein kinase (p38 MAPK) pathways and activation of 5'-AMP-dependent kinase as indicated by their altered phosphorylation, contributing to the proautophagic activities of PLB in both cell lines. Furthermore, SB202190, a selective inhibitor of p38 MAPK, and wortmannin, a potent, irreversible, and selective PI3K inhibitor, remarkably enhanced PLB-induced autophagy in PANC-1 and BxPC-3 cells, indicating the roles of PI3K and p38 MAPK mediated signaling pathways in PLB-induced autophagic cell death in both cell lines. In addition, PLB significantly inhibited epithelial to mesenchymal transition phenotype in both cell lines with an increase in the expression level of E-cadherin and a decrease in N-cadherin. Moreover, PLB treatment significantly suppressed the expression of Sirt1 in both cell lines. These findings show that PLB promotes cell cycle arrest and autophagy but inhibits epithelial to mesenchymal transition phenotype in pancreatic cancer cells with the involvement of PI3K/protein kinase B/mammalian target of rapamycin and p38 MAPK mediated pathways.

Pancreatic cancer is the most aggressive cancer worldwide with poor response to current therapeutics. Alisertib (ALS), a potent and selective Aurora kinase A inhibitor, exhibits potent anticancer effects in preclinical and clinical studies; however, the effect and underlying mechanism of ALS in the pancreatic cancer treatment remain elusive. This study aimed to examine the effects of ALS on cell growth, autophagy, and epithelial-to-mesenchymal transition (EMT) and to delineate the possible molecular mechanisms in human pancreatic cancer PANC-1 and BxPC-3 cells. The results showed that ALS exerted potent cell growth inhibitory, pro-autophagic, and EMT-suppressing effects in PANC-1 and BxPC-3 cells. ALS remarkably arrested PANC-1 and BxPC-3 cells in G2/M phase via regulating the expression of cyclin-dependent kinases 1 and 2, cyclin B1, cyclin D1, p21 Waf1/Cip1, p27 Kip1, and p53. ALS concentration-dependently induced autophagy in PANC-1 and BxPC-3 cells, which may be attributed to the inhibition of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR), p38 mitogen-activated protein kinase (p38 MAPK), and extracellular signal-regulated kinases 1 and 2 (Erk1/2) but activation of 5'-AMP-dependent kinase signaling pathways. ALS significantly inhibited EMT in PANC-1 and BxPC-3 cells with an increase in the expression of E-cadherin and a decrease in N-cadherin. In addition, ALS suppressed the expression of sirtuin 1 (Sirt1) and pre-B cell colony-enhancing factor/visfatin in both cell lines with a rise in the level of acetylated p53. These findings show that ALS induces cell cycle arrest and promotes autophagic cell death but inhibits EMT in pancreatic cancer cells with the involvement of PI3K/Akt/mTOR, p38 MAPK, Erk1/2, and Sirt1-mediated signaling pathways. Taken together, ALS may represent a promising anticancer drug for pancreatic cancer treatment. More studies are warranted to investigate other molecular targets and mechanisms and verify the efficacy and safety of ALS in the treatment of pancreatic cancer.

Mammalian target of rapamycin (mTOR) signaling pathways have been shown to be activated in thyroid cancer. Recent evidences have demonstrated that the antidiabetic agent metformin, an activator of 5'-AMP-activated protein kinase, can impair the proliferation and migration of cancer cells via inhibition of mTOR. However, the underlying mechanisms remain unclear. In this study, we show that metformin can inhibit mTOR pathway to impair growth and migration of the thyroid cancer cell lines. Cyclin D1 and c-Myc are important regulators of cancer cell growth, and we observed that treatment of thyroid cancer cells with metformin reduced c-Myc and cyclin D1 expression through suppression of mTOR and subsequent inhibition of P70S6K1 and 4E-BP1 phosphorylation. Metformin reduced epithelial to mesenchymal transition (EMT) in thyroid carcinoma cells. Moreover, metformin regulated expression of the EMT-related markers E-cadherin, N-cadherin, and Snail. Additionally, knockdown of TSC2, the upstream regulatory molecule of mTOR pathway, or treatment of rapamycin, the mTOR inhibitor, could abolish the effects of metformin to regulate thyroid cancer cell proliferation, migration, EMT, and mTOR pathway molecules. These results indicate that metformin can suppress the proliferation, migration, and EMT of thyroid cancer cell lines by inhibiting mTOR signaling. These findings suggest that metformin and its molecular targets may be useful in thyroid carcinoma therapy.

The epithelial-mesenchymal transition (EMT) plays a significant role in renal tubulointerstitial fibrosis (TIF), which is one of hallmark pathological feature of diabetic nephropathy (DN). Angiotensin II via its type-1 receptor AT1R is involved in the development of TIF. The purpose of our study was aimed to investigate the effect of silencing of AT1R on EMT and elucidate the possible mechanism underling these effects. EMT was induced by high glucose (HG) in human proximal tubular epithelial cell line HK-2 cells. The mRNA levels of AT1R were determined. The expression of AT1R was silenced by small interfering RNA (siRNA) technology and confirmed by quantitative real time PCR (qRT-PCR). After transfection with siAT1R, cell viability and expression levels of epithelial cell marker (epithelial (E)-cadherin), mesenchymal cell marker (alpha-smooth muscle actin (alpha-SMA)), four transcriptional factors (snail, slug, twist, and ZEB-1) were determined, as well as the roles of mechanistic target of rapamycin (mTOR)/p70S6K signaling pathway. The levels of AT1R were significantly higher after exposure to HG (P < 0.05). Transfection with siAT1R had no effect on cell viability, but reversed HG-induced EMT by up-regulation of E-cadherin expression and decrease of alpha-SMA, snail, and twist levels. MTOR/p70S6K signaling pathway was highly activated in HK-2 cells cultured under HG, but was inhibited by transfection with siAT1R. Our results suggest that silencing of AT1R inhibits EMT induced by HG in HK-2 cells via inactivation of mTOR/p70S6K signaling pathway. Silencing of AT1R might be a new strategy to treat DN.CI - Copyright (c) 2015 Elsevier Inc. All rights reserved.

Recent studies indicate that a high level of nesfatin-1/Nucleobindin-2 (NUCB-2) is associated with poor outcome and promotes cell migration in breast cancer and prostate cancer. However, the role of NUCB2 is not well known in colon cancer. In this study, NUCB-2 level in colon cancer tissue was higher than that in non-tumor tissue. Suppression of NUCB-2 in a colon cancer cell line SW620 inhibited migration and invasion. The microarray analysis showed that low expression level of transcription factor ZEB1 in NUCB-2 knockdowned SW620 cells. In addition, expression level of epithelial-mesenchymal transition (EMT)-related molecules including N-cadherin, E-cadherin, beta-catenin, Slug and Twist was affected by NUCB-2 suppression and ZEB1-denepdent pathway. The signaling pathway liver kinase B1(LKB1)/AMP-dependent protein kinase (AMPK)/target of rapamycin complex (TORC) 1 was involved in regulation of NUCB-2-mediated metastasis and EMT properties. Suppression of NUCB-2 inhibited tumor nodules formation in a murine colon tumor model as well. In summary, nesfatin-1/NUCB-2 enhanced migration, invasion and EMT in colon cancer cells through LKB1/AMPK/TORC1/ZEB1 pathways in vitro and in vivo.

Inactivating mutations of the TSC1/TSC2 complex (TSC1/2) cause tuberous sclerosis (TSC), a hereditary syndrome with neurological symptoms and benign hamartoma tumours in the brain. Since TSC effectors are largely unknown in the human brain, TSC patient cortical tubers were used to uncover hyperphosphorylation unique to TSC primary astrocytes, the cell type affected in the brain. We found abnormal hyperphosphorylation of catenin delta-1 S268, which was reversible by mTOR-specific inhibitors. In contrast, in three metastatic astrocytoma cell lines, S268 was under phosphorylated, suggesting S268 phosphorylation controls metastasis. TSC astrocytes appeared epithelial (i.e. tightly adherent, less motile, and epithelial (E)-cadherin positive), whereas wild-type astrocytes were mesenchymal (i.e. E-cadherin negative and highly motile). Despite their epithelial phenotype, TSC astrocytes outgrew contact inhibition, and monolayers sporadically generated tuberous foci, a phenotype blocked by the mTOR inhibitor, Torin1. Also, mTOR-regulated phosphokinase C epsilon (PKCe) activity induced phosphorylation of catenin delta-1 S268, which in turn mediated cell-cell adhesion in astrocytes. The mTOR-dependent, epithelial phenotype of TSC astrocytes suggests TSC1/2 and mTOR tune the phosphorylation level of catenin delta-1 by controlling PKCe activity, thereby regulating the mesenchymal-epithelial-transition (MET). Thus, some forms of TSC could be treated with PKCe inhibitors, while metastasis of astrocytomas might be blocked by PKCe stimulators.CI - (c) The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Posterior capsule opacification (PCO) is the most common complication that causes visual decrease after extracapsular cataract surgery. The primary cause of PCO formation is the proliferation of the residual lens epithelial cells (LECs). The mammalian target of rapamycin (mTOR) plays an important role in the growth and migration of LECs. In the current study, we used small interfering RNA (siRNA) to specifically attenuate mTOR in human lens epithelial B3 cells (HLE B3). We aimed to examine the effect of mTOR-siRNA on the proliferation, migration and epithelial-to-mesenchymal transition (EMT) of HLE B3 cells and explore the underlying mechanisms. The mTOR-siRNA was transfected into HLE B3 cells using lipofectamine 2000. The mRNA and protein levels of mTOR were examined to confirm the efficiency of mTOR-siRNA. The levels of mRNA and protein as well as the activity of mTOR down-stream effectors p70 ribosomal protein S6 kinase (p70S6K) and protein kinase B (PKB, AKT) were examined using real-time PCR or Western blot, respectively. The cell proliferation was determined using cell counting kit (CCK) 8 and cell growth curve assay. The cell migration was examined using Transwell system and Scratch assay. MTOR-siRNA effectively eliminated mTOR mRNA and protein. The proliferation and migration were significantly suppressed by mTOR-siRNA transfection. mTOR-siRNA reduced the mRNA of p70S6K and AKT in a time-dependent manner. Furthermore, the phosphorylation of p70S6K and AKT was decreased by mTOR-siRNA. MTOR-siRNA also eliminated the formation of mTORC1 and mTORC2 protein complex and blocked the transforming growth factor (TGF)-beta-induced EMT. Our results suggested that mTOR-siRNA could effectively inhibit the proliferation, migration and EMT of HLE B3 cells through the inhibition of p70S6K and AKT. These results indicated that mTOR-siRNA might be an effective agent inhibiting HLE cells growth and EMT following cataract surgery and provide an alternative therapy for preventing PCO.

Renal fibrosis contributes to declining renal function in the elderly. What is unclear however, is whether epithelial-mesenchymal transition (EMT) contributes to this age-related renal fibrosis. Here, we analyzed indicators of EMT during kidney aging and investigated the protective effects and mechanisms of short-term regimens of caloric restriction (CR) or caloric restriction mimetics (CRMs), including resveratrol and metformin. High glucose was used to induce premature senescence and EMT in human primary proximal tubular cells (PTCs) in vitro. To test the role of AMPK-mTOR signaling, siRNA was used to deplete AMPK. Cellular senescence and AMPK-mTOR signaling markers associated with EMT were detected. CR or CRMs treatment alleviated age-related EMT in aging kidneys, which was accompanied by activation of AMPK-mTOR signaling. High glucose induced premature senescence and EMT in PTCs in vitro, which was accompanied by down-regulation of AMPK/mTOR signaling. CRMs alleviated high glucose-induced senescence and EMT via stimulation of AMPK/mTOR signaling. Activation of AMPK/mTOR signaling protected PTCs from high glucose-induced EMT and cellular senescence. Short-term regimens of CR and CRMs alleviated age-related EMT via AMPK-mTOR signaling, suggesting a potential approach to reducing renal fibrosis during aging.

OBJECTIVE: Bleomycin (BLM) has been found safe and highly effective in the treatment of the mucoceles by intralesional injection in our previous study. The present research was designed to investigate whether epithelial-to-mesenchymal transition (EMT) contributes to the therapeutic effects of BLM for mucoceles of the salivary glands. MATERIAL AND METHODS: The cell proliferation and apoptosis of human submandibular gland cells (HSG cells) were examined by Cell Counting Kit-8 assay and Annexin V binding assay respectively. epithelial and mesenchymal markers of HSG cells were measured by real-time quantitative PCR and Western blot analysis. Acinar differentiation and cell migration assays were performed to evaluate HSG cells function. RESULTS: High-dose BLM (>/=0.5mug/mL) significantly inhibited the cell proliferation and induced the cell apoptosis, while the treatment with low-dose BLM (0.05 and 0.1mug/mL) for 48h induced EMT in HSG cells. Furthermore, Akt/mTOR pathway, rather than MAPK pathway, was activated through treated with 0.05 and 0.1mug/mL BLM, as well as activation of the transcription factor Slug and Zeb 1. The migration of HSG cells was also enhanced through 0.05 and 0.1mug/mL BLM, but the ability of acinar differentiation was diminished. CONCLUSION: Our results indicated that an EMT process was involved in the BLM-induced therapeutic effects on the HSG cells through the Akt/mTOR pathway. Importantly, the results indicated the potential role of this process in the BLM sclerotherapy of mucoceles of the salivary glands.CI - Copyright (c) 2017 Elsevier Masson SAS. All rights reserved.

BACKGROUND epithelial-mesenchymal transition (EMT) plays an important role in cancer tumorigenesis. Transforming growth factor beta1 (TGF-beta1) can induced EMT, which could increase tumor migration and invasion. Moreover, recent studies have been proven that mammalian target of rapamycin (mTOR) is a critical regulator of EMT. We investigated the mechanisms of mTOR in transforming growth factor beta1 (TGF-beta1)-induced EMT in cervical cancer cells. MATERIAL AND METHODS HeLa and SiHa cells were treated with 10 ng/ml TGF-beta1 to induce EMT. Then, they were treated with or without rapamycin. CCK8 assay was performed to determine cell proliferation. Cell migration was detected by wound-healing assay; apoptosis was analyzed by flow cytometry; mTOR inhibitors inhibited mTOR pathway to assess the expression of E-cadherin, Vimentin STAT3, Snail2, p-p70s6k, and PKM2 expression. RESULTS TGF-beta1 promoted proliferation and migration, and attenuated apoptosis in cervical carcinoma cells. Rapamycin abolished TGF-beta1-induced EMT cell proliferation and migration and reversed TGF-beta1-induced EMT. E-cadherin were suppressed, whereas Vimentin and PKM2 were increased in HeLa and SiHa cells after stimulation with TGF-beta1. Moreover, mTOR was activated in the process of TGF-beta1-induced EMT. Rapamycin inhibited the phosphorylation of p70s6k. Furthermore, inhibition of the mTOR pathway decreased PKM2 expression. CONCLUSIONS Inhibition of the mTOR pathway abolished TGF-beta1-induced EMT and reduced mTOR/p70s6k signaling, which downregulated PKM2 expression. Our results provide novel mechanistic insight into the anti-tumor effects of inhibition of mTOR.

Chemokine (CC motif) ligand 18 (CCL18) is involved in remodeling of the tumor microenvironment and plays critical roles in oncogenesis, invasiveness, and metastasis. We previously investigated the overexpression of CCL18 in primary oral squamous cell carcinoma (OSCC) tissues and its association with advanced clinical stage in OSCC patients. However, the underlying mechanisms of this CCL18-derived activity remains unidentified. This study showed exogenous CCL18 increased cell migration and invasion and induced cell epithelial-mesenchymal transition (EMT), and that E-cadherin, an epithelial marker, decreased and N-cadherin, a mesenchymal marker, increased, compared to negative control in OSCC cells. Furthermore, we detected that CCL18 induced the acquisition of cancer stem(-like) cell characteristics in oral cancer cells, but also found a significantly positive correlation between the expression of CCL18 and Bmi-1 (P < 0.001) in OSCC surgical specimens by immunohistochemistry analysis. The expression of octamer-binding transcription factor 4 and Bmi-1 were significantly upregulated, and proportions of aldehyde dehydrogenase(high+) cells and CD133(+) cells were markedly increased in CCL18-treated cells compared to untreated cells. Sphere formation ability was observably enhanced when cells were continually exposed to high levels of CCL18. Moreover, CCL18 upregulated Slug expression by stimulating the mammalian target of rapamycin (mTOR) signaling pathway in OSCC cell lines. Inhibition of the mTOR pathway by INK128, or Slug knockdown by RNA interference, reversed CCL18-induced EMT and the stemness response at both molecular and functional levels. In conclusion, our data suggested that CCL18 upregulated Slug expression to promote EMT and stem cell-like features by activating the mTOR pathway in oral cancer. These findings provide new potential targets for the early diagnosis and treatment of OSCC.CI - (c) 2017 The Authors. cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese cancer Association.

PURPOSE: Hyperfibrinogenemia is associated with unfavorable prognosis and advanced tumor behavior in various malignancies, including esophageal squamous cell carcinoma (ESCC). However, its biological function in ESCC is unknown. The present study was designed to further validate the prognostic value of preoperative plasma hyperfibrinogenemia and evaluate the biological role of fibrinogen, as well as the underlying mechanism in ESCC. METHODS: Data from 452 cases with newly diagnosed ESCC followed by curative surgery between 2006 and 2010 were retrospectively evaluated. The Clauss method was utilized to measure the preoperative plasma fibrinogen level. Correlations between the fibrinogen level and clinicopathologic characteristics and survival analysis were performed. The effects of fibrinogen on malignant behaviors, including tumor cell viability, colony formation, migration, and invasion, were also investigated. RESULTS: The optimal cut-off value for plasma fibrinogen level was defined as 4.0 g/L according to recommendations. Thus, the proportion of hyperfibrinogenemia was 24.8% (112/452). Preoperative plasma hyperfibrinogenemia was significantly associated with advanced tumor length, deep tumor invasion, advanced tumor-node-metastasis stage, alcohol consumption, a higher white blood cell count, a higher platelet count, and high globulin levels. Univariate survival analysis revealed that compared to those with normal plasma fibrinogen levels, patients with hyperfibrinogenemia tended to have poorer disease-free survival (DFS) [hazard ratio (HR), 1.692; 95% confidence interval (CI), 1.304-2.196; P < 0.001] and overall survival (OS) (HR 1.864; 95% CI 1.424-2.440; P < 0.001). In the multivariate Cox regression models, these factors remained independent predictors for impaired DFS (HR 1.491; 95% CI 1.138-1.955; P = 0.004) and OS (HR 1.648; 95% CI 1.246-2.180; P < 0.001) after adjusting for other confounding variables. In addition, fibrinogen could significantly promote cell migration and invasion but not proliferation. Moreover, it could also induce epithelial-mesenchymal transition (EMT) and increase the levels of p-PTEN, p-AKT, and p-mTOR in ESCC cell lines. CONCLUSIONS: Preoperative plasma hyperfibrinogenemia might serve as an independent predictor of unfavorable survival in ESCC. Furthermore, fibrinogen may promote cell motility by inducing EMT via the p-AKT/p-mTOR pathway.

The AKT/PI3K/mTOR pathway is frequently altered in a range of human tumours, including bladder cancer. Here we report the phenotype of mice characterised by deletion of two key players in mTOR regulation, Pten and Lkb1, in a range of tissues including the mouse urothelium. Despite widespread recombination within the range of epithelial tissues, the primary phenotype we observe is the rapid onset of bladder tumorigenesis, with median onset of approximately 100 days. Single deletion of either Pten or Lkb1 had no effect on bladder cell proliferation or tumour formation. However, simultaneous deletion of Lkb1 and Pten led to an upregulation of the mTOR pathway and the hypoxia marker GLUT1, increased bladder epithelial cell proliferation and ultimately tumorigenesis. Bladder tissue also exhibited characteristic features of epithelial-mesenchymal transition, with loss of the epithelial markers E-cadherin and the tight junction protein ZO-1, and increases in the mesenchymal marker vimentin as well as nuclear localization of epithelial-mesenchymal transition (EMT) regulator Snail. We show that these effects were all dependent upon mTOR activity, as rapamycin treatment blocked both EMT and tumorigenesis. Our data therefore establish clear synergy between Lkb1 and Pten in controlling the mTOR pathway within bladder epithelium, and show that loss of this control leads to the disturbance of epithelial structure, EMT and ultimately tumorigenesis.