Revisiting mTOR and Epithelial-Mesenchymal Transition.
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ABSTRACT:
SUBMITTER: Herrerias MM
PROVIDER: S-EPMC7258817 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Epithelial-mesenchymal transition (EMT) is an important process in embryonic development, fibrosis, and cancer metastasis. During cancer progression, the activation of EMT permits cancer cells to acquire migratory, invasive, and stem-like properties. A growing body of evidence supports the critical link between EMT and cancer stemness. However, contradictory results have indicated that the inhibition of EMT also promotes cancer stemness, and that mesenchymal-epithelial transition, the reverse process of EMT, is associated with the tumor-initiating ability required for metastatic colonization. The concept of 'intermediate-state EMT' provides a possible explanation for this conflicting evidence. In addition, recent studies have indicated that the appearance of 'hybrid' epithelial-mesenchymal cells is favorable for the establishment of metastasis. In summary, dynamic changes or plasticity between the epithelial and the mesenchymal states rather than a fixed phenotype is more likely to occur in tumors in the clinical setting. Further studies aimed at validating and consolidating the concept of intermediate-state EMT and hybrid tumors are needed for the establishment of a comprehensive profile of cancer metastasis.
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Project description:BackgroundTumor microenvironments (TMEs) activate various axes/pathways, predominantly inflammatory and hypoxic responses, impact tumorigenesis, metastasis and therapeutic resistance significantly. Although molecular pathways of individual TME are extensively studied, evidence showing interaction and crosstalk between hypoxia and inflammation remain unclear. Thus, we examined whether interferon (IFN) could modulate both inflammatory and hypoxic responses under normoxia and its relation with cancer development.MethodsIFN was used to induce inflammation response and HIF-1α expression in various cancer cell lines. Corresponding signaling pathways were then analyzed by a combination of pharmacological inhibitors, immunoblotting, GST-Raf pull-down assays, dominant-negative and short-hairpin RNA-mediated knockdown approaches. Specifically, roles of functional HIF-1α in the IFN-induced epithelial-mesenchymal transition (EMT) and other tumorigenic propensities were examined by knockdown, pharmacological inhibition, luciferase reporter, clonogenic, anchorage-independent growth, wound-healing, vasculogenic mimicry, invasion and sphere-formation assays as well as cellular morphology observation.ResultsWe showed for the first time that IFN induced functional HIF-1α expression in a time- and dose- dependent manner in various cancer cell lines under both hypoxic and normoxic conditions, and then leading to an activated HIF-1α pathway in an IFN-mediated pro-inflammatory TME. IFN regulates anti-apoptosis activity, cellular metastasis, EMT and vasculogenic mimicry by a novel mechanism through mainly the activation of PI3K/AKT/mTOR axis. Subsequently, pharmacological and genetic modulations of HIF-1α, JAK, PI3K/AKT/mTOR or p38 pathways efficiently abrogate above IFN-induced tumorigenic propensities. Moreover, HIF-1α is required for the IFN-induced invasiveness, tumorigenesis and vasculogenic mimicry. Further supports for the HIF-1α-dependent tumorigenesis were obtained from results of xenograft mouse model and sphere-formation assay.ConclusionsOur mechanistic study showed an induction of HIF-1α and EMT ability in an IFN-mediated inflammatory TME and thus demonstrating a novel interaction between inflammatory and hypoxic TMEs. Moreover, targeting HIF-1α may be a potential target for inhibiting tumor tumorigenesis and EMT by decreasing cancer cells wound healing and anchorage-independent colony growth. Our results also lead to rationale guidance for developing new therapeutic strategies to prevent relapse via targeting TME-providing IFN signaling and HIF-1α programming.
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Project description:BackgroundRab22a is a member of the RAS superfamily, involved in early endosome formation and intracellular vesicle transport. Rab22a is significantly upregulated in a variety of malignant tumors. However, its function in thyroid cancer has never been addressed.MethodsThe expression of Rab22a in paraffin sections of 101 patients was detected by immunohistochemical staining. By upregulating and downregulating the expression of Rab22a in thyroid cancer cell lines, the effect of Rab22a on cell proliferation, invasion, and migration was analyzed. Co-IP was employed, and the interaction between Rab22a and PI3Kp85α was shown. The function of Rab22a on PI3K/AKT/mTOR signaling and epithelial-mesenchymal transition (EMT) was further studied by western blot analysis.ResultsImmunostaining showed that Rab22a was significantly overexpressed in thyroid cancer tissues but negative in adjacent normal tissues or nodular goiters. The proliferation, migration, invasion, and EMT in papillary thyroid carcinoma cell lines were enhanced upon Rab22a overexpression but inhibited after knocking down Rab22a. The co-IP assay demonstrated an interaction between Rab22a and PI3K85α, an effector of PI3K. We further found that Rab22a can activate the PI3K/AKT/mTOR signaling pathway. However, the ability of Rab22a to promote the proliferation, invasion, migration, and EMT of papillary thyroid carcinoma cells was significantly inhibited after being treated with LY294002, a PI3K inhibitor.ConclusionsRab22a can promote the EMT process and enhance proliferation, migration, and invasion of papillary thyroid carcinoma cells by activating the PI3K/AKT/mTOR signaling pathway. Our study provides new pathological diagnosis clues and clinical treatment targets for thyroid cancer.
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Project description:Versican is a large extracellular chondroitin sulfate proteoglycan that belongs to the family of lecticans. Alternative splicing of versican generates at least four isoforms named V0, V1, V2, and V3. We show here that ectopic expression of versican V1 isoform induced mesenchymal-epithelial transition (MET) in NIH3T3 fibroblasts, and inhibition of endogenous versican expression abolished the MET in metanephric mesenchyme. MET in NIH3T3 cells was demonstrated by morphological changes and dramatic alterations in both membrane and cytoskeleton architecture. Molecular analysis showed that V1 promoted a "switch" in cadherin expression from N- to E-cadherin, resulting in epithelial specific adhesion junctions. V1 expression reduced vimentin levels and induced expression of occludin, an epithelial-specific marker, resulting in polarization of V1-transfected cells. Furthermore, an MSP (methylation-specific PCR) assay showed that N-cadherin expression was suppressed through methylation of its DNA promoter. Exogenous expression of N-cadherin in V1-transfected cells reversed V1's effect on cell aggregation. Reduction of E-cadherin expression by Snail transfection and siRNA targeting E-cadherin abolished V1-induced morphological alteration. Transfection of an siRNA construct targeting versican also reversed the changed morphology induced by V1 expression. Silencing of endogenous versican prevented MET of metanephric mesenchyme. Taken together, our results demonstrate the involvement of versican in MET: expression of versican is sufficient to induce MET in NIH3T3 fibroblasts and reduction of versican expression decreased MET in metanephric mesenchyme.
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Project description: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.
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Project description:BackgroundN6-methyladenosine (m6A) modification, as the most abundant RNA modification, widely participates in the physiological process and is involved in multiple disease progression, especially cancer. YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) is a pivotal m6A "reader" protein, which has been reported in multiple cancers. However, the role and molecular mechanism of YTHDF1 in HCC are still not fully elucidated.MethodsBased on various bioinformatics databases, q-RT PCR, western blot, and a tissue microarray containing 90 HCC samples, we examined the expression of YTHDF1 in HCC. Then, we applied the loss-of-function experiments to explore the role of YTHDF1 in HCC by in vitro and in vivo assays. Finally, we performed the gene set enrichment analysis (GSEA) to predict the potential signaling pathway of YTHDF1 involved in HCC and further verified this prediction.ResultsYTHDF1 was overexpressed in HCC and associated with HCC grade. Depletion of YTHDF1 markedly impaired the proliferation, migration, invasion, and cell cycle process of HCC cells. Mechanistically, YTHDF1 promoted the growth of HCC cells via activating the PI3K/AKT/mTOR signaling pathway. Moreover, we also demonstrated that the epithelial-mesenchymal transition (EMT) mediated the promoting effect of YTHDF1 on the migration and invasion of HCC cells.ConclusionsYTHDF1 contributes to the progression of HCC by activating PI3K/AKT/mTOR signaling pathway and inducing EMT.
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Project description:The epithelial-mesenchymal transition (EMT) is a developmental program that enables stationary epithelial cells to gain the ability to migrate and invade as single cells. Tumor cells reactivate EMT to acquire molecular alterations that enable the partial loss of epithelial features and partial gain of a mesenchymal phenotype. Our understanding of the contribution of EMT to tumor invasion, migration, and metastatic outgrowth has evolved over the past decade. In this review, we provide a summary of both historic and recent studies on the role of EMT in the metastatic cascade from various experimental systems, including cancer cell lines, genetic mouse tumor models, and clinical human breast cancer tissues.
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