Epithelial to mesenchymal transition is impaired in colon cancer cells with microsatellite instability.
OBJECTIVE
Colorectal cancers (CRCs) displaying DNA microsatellite instability (MSI) are associated with a favorable natural history, but the molecular basis for this observation has not been defined. We sought to determine whether the epithelial to mesenchymal transition (EMT) is impaired in MSI-positive CRCs that characteristically have a mutant transforming growth factor-beta receptor type II (TGFBR2) gene.


METHODS
The induction of EMT by transforming growth factor-beta1 (TGF-beta1) was analyzed by phase contrast microscopy, immunofluorescence, quantitative reverse transcription polymerase chain reaction, immunoblotting, and cellular migration, and invasion assays. Expression of EMT markers was evaluated by immunohistochemistry and quantitative reverse transcription polymerase chain reaction in a series of human colorectal tumors.


RESULTS
TGF-beta1 induced changes in cellular morphology, gene expression, motility, and invasion consistent with EMT in microsatellite stable (MSS) colon cancer cells, whereas cells with MSI and mutant TGFBR2 were unresponsive to TGF-beta1. These effects did not require Smad4, but depended on the recruitment of extracellular signal-regulated kinase. Tumor cells with MSI but wild-type TGFBR2 underwent EMT in response to TGF-beta1, indicating that TGFBR2 genotype is a key determinant of the EMT response in tumors with MSI. In human colorectal tumors, expression of EMT markers was significantly associated with adverse clinicopathologic features and the absence of MSI.


CONCLUSIONS
These findings define a unique genotype-phenotype relationship between TGFBR2 and EMT that may contribute to the improved prognosis consistently observed in colon cancers with MSI.
Pino
Maria S
MS
Gastrointestinal Unit, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Kikuchi
Hirotoshi
H
Zeng
Min
M
Herraiz
Maria-Teresa
MT
Sperduti
Isabella
I
Berger
David
D
Park
Do-Youn
DY
Iafrate
A John
AJ
Zukerberg
Lawrence R
LR
Chung
Daniel C
DC
D021581:Active Transport, Cell Nucleus; D000328:Adult; D000368:Aged; D015820:Cadherins / Q000032:analysis; D054337:Cell Dedifferentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D003110:Colonic Neoplasms / Q000235:genetics* / Q000473:pathology*; D004847:Epithelial Cells / Q000473:pathology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008648:Mesoderm / Q000473:pathology*; D053842:Microsatellite Instability; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics; D051899:Smad2 Protein / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
D015820:Cadherins; D018125:Receptors, Transforming Growth Factor beta; C497782:SMAD2 protein, human; D051899:Smad2 Protein; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II