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Epithelial Mesenchymal Transitions (EMT)
In Cancer Metastasis
Greg Longmore, February 19, 2008
Reviews
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J.P. Thiery and J.P. Sleeman Nature Rev. Mol. Cell Biol. 7:131-142, 2006
H. Peinado et al., Nature Rev. Cancer 7:415-428, 2007
A. Barrallo-Gimeno and M.A. Nieto. Development 132:3150-61, 2005
J.P. Thiery. Nature Rev. Cancer 2:442-54, 2002
Post-Transcriptional Regulation of Snail/EMT
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A. Cano et al., Nat. Cell Biol. 2:76-83, 2000
B.P. Zhou et al., Nat. Cell Biol. 6:931-40, 2004
Z. Yang et al., Cancer Res. 65:3179-84, 2005
H. Peinado et al., EMBO J. 24:3446-58, 2005
J.I. Yok et al., Nat. Cell Biol. 8:1389-406, 2006
E. Langer et al., Dev. Cell March 11, 2008
Breast Cancer
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S.E. Moody et al., Cancer Cell 8:197-209, 2005
N. Fujita et al., Cell 113:207-19, 2003
C. Xue et al., Cancer Res. 63:3386-94, 2003
A. Dhasarathy et al., Mol. Endocrinology 21:2907-18, 2007
OUTLINE
1.
Cancer Metastasis
2. EMT - MET - definitions
3. In Normal Development
4. In Adult Pathology
5. Signals that Induce EMT
6. Snail Family
- Transcriptional regulators of EMT
7. Clinical - Breast Cancer
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.)
Cancer Metastasis
INVASION
EMT
MET
EMT in Development
Gastrulation
Epithelial
Neural Crest Delamination
Mesenchymal
EMT in the Adult
- epithelia wound healing (skin)
- tissue fibrosis in response to injury (lung, kidney, liver)
- epithelial cancer metastasis
Skin wound healing
Slug expression
Epithelial Mesenchymal Transition (EMT)
Altered Cell Morphology
Breakdown of
Intercellular Junctions
Increased Cell Motility /
Invasiveness
Mesenchymal Epithelial Transition (MET)
Cellular changes during EMT
Lost or decreased
1. Epithelial adhesion receptors - E-cadherin, Occludin, Claudins
2. -catenin, -catenin frequently translocates to nucleus (Wnt)
3. Circumferential F-actin fibers
4. Epithelial cytokeratins
5. Apico-basal polarity
Acquired
1. Intermediate filament protein - Vimentin
2. Matrix metalloproteinases secreted, produced
3. Fibronectin secretion
4. N-cadherin
5. -smooth muscle actin (myofibroblasts)
6. v6 integrin
7. Motility, Invasiveness
Epithelial Cells
Apical Surface
Tight junction
Adherens junction
Desmosome
Gap junction
focal adhesions
Basolateral Surface
Epithelial cell-cell adhesive complexes: general organization
transmembrane receptor
outside
cytoplasmic plaque proteins
“scaffolding / adapter proteins”
inside
signal
transduction
Cytoskeletal elements
proliferation
cell fate
Adherens Junctions: Cadherins - catenins - Actin
polarity
E-cadherin and Cancer pathogenesis
“A metastasis tumor suppressor gene?”
1. Mouse models - TAG-insulinomas
2. Germline mutations in CDH1 strongly predispose individuals to
gastric cancer and breast cancer
3. Somatic inactivating mutations in CDH1 in gastric cancers and
infiltrative lobular breast cancers
4. But in the majority of cancers where CDH1 expression is lost
mutations are rare or absent
(? Epigenetics or trans-acting factors)
Colon Cancer
E-cadherin (brown)
Does EMT occur in vivo?
transformed
human mammary cells
implanted in a
mouse
Other Data
Lung Fibrosis model:
- -gal transgenic mice + TGFgenerate
-gal + myofibroblasts
PyV-mT, FSP1.TK mice - less invasion and
Metastasis following treatment with GCV
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
QuickTime™ and a
decompressor
are needed to see this picture.
+ Snail
The Snail family of transcriptional
repressors
SNAG Domain
Zinc Fingers
Snail
264aa
Slug
269aa
Smuc
292aa
Scratch 348aa
FGF
Wnt
Neural crest
Neural crest
Gastrulation
Heart dev’pt
Limb dev’pt
Tumor metastasis
Tumor metastasis
TGF
EGF
BMP
Skin
Mammary dev’pt
Neural crest
Palate fusion
gastrulation
L/R asymmetry
Tissue fibrosis
Tumor metastasis
Heart dev’pt
Tumor metastasis
Snail or Slug
MTA3
GSK3-mediated
phosphorylation
Estrogens
BUT,
There is only a modest inverse relationship between
Snail and E-cadherin expression (IHC, mRNA)
in many metastatic cancers
With possibly one exception - breast cancer (see later)
Snail Modification/Function
GSK3
cytoplasmic
destruction
GSK3
nuclear export
93 - SDEDSGKGSQPPSPPSPAPSSFSSTSVSSLE- 122
SNAG Domain
K98
K137
Zinc Fingers
S246
Pak1
LOX 2/3
Ajuba LIM proteins:
- adapters that assemble
repressor complex (co-repressors)
Inhibit GSK3 - increase Snail - decrease E-cadherin - metastasis
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
How a Wnt signal cooperates with Snail to influence metastasis
Wnt - Axin2(mRNA) - GSK3 nuclear-cytoplasm - Snail nuclear - EMT/Invasion
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
Remember Wnt also inhibits GSK3
- stabilizes Snail, and
- results in nuclear translocation of -catenin
Snail or Slug functions
Epithelial
Markers
Proliferation
Cyclin D
E-cadherin
CDK4
Claudins
Occludins Rb phosph
p21
Desmoplakin
Cytokeratins
Mesenchymal
Cell shape changes
markers
Cell movements, invasion
Fibronectin
Vitronectin
Vimentin
RhoB
MMPs
Survival
PI3K activity
ERK activity
Caspases
P53
BID