Epithelial-Mesenchymal Transition (EMT) - PDF

Epihtelial-Mesechymal Transition Mol & Cell Biology MD105 Prof A. Stephanou  Objectives Understand the process and features of EMT How EMT proceeds What factors modulate EMT Understand howEMT in development and disease Know that EMT alteration associated with ca...

Epihtelial-Mesechymal Transition Mol & Cell Biology MD105 Prof A. Stephanou  Objectives Understand the process and features of EMT How EMT proceeds What factors modulate EMT Understand howEMT in development and disease Know that EMT alteration associated with cancer metastasis  DEFINITION: EMT An orchestrated series of events in which cell- cell and cell-extracellular matrix (ECM) interactions are altered to release epithelial cells from the surrounding tissue, the cytoskeleton is reorganized to allow movement in 3 dimensions in the ECM and a new transcriptional program is induced to maintain the mesenchymal phenotype  Cell Types Epithelial cells Mesenchymal cells All animals start as epithelial cells NOTE: Both types can form all three germ layers, ectoderm, mesoderm and endoderm (?) Characteristics of Epithelial Cells Typically a sheet 1 cell thick Individual cells abutting/joining each other Regularly spaced cell junctions and adhesions between neighboring cells Tight adhesion between cells resulting in inhibition of movement away from the monolayer  Epithelium (cont.) Enclose a 3-dimensional space within the monolayer Gives structural definition and rigidity Epithelial sheet is polarized (resting state: negative charge inside the cell membrane compared to the outside) Apical and basal surfaces often very different – Adheres to different substrates (ECM) – Has different cellular function  Epithelial Cells Apical Surface Tight junction Adherens junction Desmosome Gap junction focal adhesions Basolateral Surface Characteristics of Mesenchymal Cells Lack regimented structure Few tight intracellular adhesions Weak adhesions which allow for ease of mobility Forms irregular structures that are not uniform in composition or density More extended and elongated in shape Epithelial and Mesenchymal Cells  EMT Markers Proteins that increase in abundance Proteins that decrease in abundance N-cadherin E-cadheren Vimentin Desmoplakin Fibronectin Cytokeratin Snail1 (Snail) Occludin Snail2(Slug) Proteins whose activity increases Twist ILK Goosecoid GSK-3ß FOXC2 Rho Sox10 Proteins that accumulate in the MMP-2 nucleus MMP-3 ß-catenin MMP9 Smad-2/3 Integrin vß6 NF- ß Snail1 (Snail) Snail2 (Slug) Twist Biochemical changes accompanying EMT Expressing Twist transcription factor in MDCK cells induces fibronectin and vimentin Transitions  EMT in Development Gastrulation Neural Crest Delamination Epithelial Mesenchymal EMT in the Adult - epithelia wound healing (skin) - tissue fibrosis in response to injury (lung, kidney, liver) - epithelial cancer metastasis  Animal Development - I Early cleavage results in a ball of cells which, usually includes a hollow space, the blastocoel. Thus the initial structure is an epithelium folded into a ball. The second phase is the formation of a Triploblastic embryo. Three primary germ layers Ectoderm Mesoderm Endoderm Process is called Gastrulation  Gastrulation Two processes involved Epithelial sheet deforms as a unit to form the archenteron or primitive gut A small number of cells at the base or vegetal plate loose contact with neighbors, tear loose for Basal lamina and crawl into blastocoel EMT in Tissues Epithelium I induces an EMT process in epithelium II (black arrows) through the secretion of inducers (purple dots). The epithelium II-derived mesenchymal population (green) is recruited by epithelium I (green-to-blue-graded arrows) and differentiates (blue cells) according to the molecular information arising from the inducing tissue (red dots).  SIGNALING Extrinsic Signals that Induce EMT: - Tumor-derived (autocrine), Stromal Cell-derived (paracrine) - FGF, TGF-, EGF, HGF (scatter factor), Wnt, TNF- - E-cadherin cleavage (MMPs) - E-cadherin endocytosis Intracellular Pathways: - PI3K - Ras - MAPK, - GSK3, NF- B, p38, Smads, STAT3 - Rac1b - ROS (MMP-3) Transcriptional regulation: - E2a/E47, FOXC2, SIP1, Snail, Slug, Twist  SIGNALING in EMT FGF Wnt TGF EGF BMP Neural crest Neural crest Skin Mammary dev’pt Neural crest Gastrulation Heart dev’pt Palate fusion gastrulation L/R asymmetry Limb dev’pt Tumor metastasis Tissue fibrosis Tumor metastasis Tumor metastasis Heart dev’pt Tumor metastasis Snail or Slug MTA3 GSK3-mediated Estrogens phosphorylation The Snail family of transcriptional repressors SNAG Domain Zinc Fingers Snail 264aa Slug 269aa Smuc 292aa Scratch 348aa EMT Signaling Pathways How do stromal cells control EMT? Role of TGF- Overview Review ofof mouse mouse lung lungdevelopment development Canalicular Pseudoglandular Saccular Alveolar Cordoso, Dev. Dyn. 219:121 (2000) Neonatology: SE Wert 5th edition 1999.  EMT and Cancer Occurrence of EMT during tumor progression allows benign tumors to infiltrate surrounding tissue and ultimately metastasize to distant sites We see EMT stages in pathological staging of tumors  What is metastasis? Tumors take many years before detection (>109 cells)- particularly if tumor growing in an extensible space. Only when tumor begins to compromise function of the organ does it evoke symptoms. Most primary tumors can be surgically excised and account for less than 10% of cancer deaths. For 90% of patients - primary successfully excised but patients die as a result of disease at sites distant to that of primary. Metastasis is the truly lethal event in cancer but also the process we know least about. Understanding metastasis has the greatest potential to extend patient survival.  What is metastasis? 1. Primary tumors (10%) rarely kill, metastases do (90%) 2. Primary tumor size often predicts for metastasis 3. Some tumors don’t metastasize (skin SCC, brain glioblastoma) while other do frequently (melanoma) 4. Some tumors have a propensity for specific tissue metastasis (breast, prostate - bone), while others are excluding from tissues - when considering blood flow as a single variable 5. “micrometastases” at diagnosis - breast, colon - worse outcomes 6. Organ fibrosis is a significant risk factor for the development of aggressive cancers (hepatic cirrhosis, lung fibrosis) 7. The metastatic process (Fig.)  How do tumors spread? The concept of the invasion-metastasis cascade: 6 distinct steps Probability of an individual cancer cell completing cascade is very small Are there metastasis genes? EMT in Tumor Progression Cancer Metastasis Cancer Metastasis Cancer Metastasis Reviews 1. J.P. Thiery and J.P. Sleeman Nature Rev. Mol. Cell Biol. 7:131-142, 2006 2. H. Peinado et al., Nature Rev. Cancer 7:415-428, 2007 3. A. Barrallo-Gimeno and M.A. Nieto. Development 132:3150-61, 2005 4. J.P. Thiery. Nature Rev. Cancer 2:442-54, 2002 Post-Transcriptional Regulation of Snail/EMT 1. A. Cano et al., Nat. Cell Biol. 2:76-83, 2000 2. B.P. Zhou et al., Nat. Cell Biol. 6:931-40, 2004 3. Z. Yang et al., Cancer Res. 65:3179-84, 2005 4. H. Peinado et al., EMBO J. 24:3446-58, 2005 5. J.I. Yok et al., Nat. Cell Biol. 8:1389-406, 2006 6. E. Langer et al., Dev. Cell March 11, 2008 Breast Cancer 1. S.E. Moody et al., Cancer Cell 8:197-209, 2005 2. N. Fujita et al., Cell 113:207-19, 2003 3. C. Xue et al., Cancer Res. 63:3386-94, 2003 4. A. Dhasarathy et al., Mol. Endocrinology 21:2907-18, 2007