BACKGROUND: In breast cancer the development of metastasis is a major turning 
point in the treatment and outcome of the disease. Throughout tumour 
development, and especially in the development of metastasis, epithelial 
mesenchymal transition takes place. During this transformation into a 
mesenchymal phenotype, the tumour cells undergo a series of structural changes. 
The loss of structural integrity and adoption of mesenchymal filaments enables 
cells to detach from the epithelial cell layer and metastasise. Keratins form 
the intermediate filaments of the cytoskeleton and provide scaffold structures 
within cells. During cancer progression the intermediate filaments are 
reorganised, and dramatic changes are seen in their protein components. Keratins 
K8, K18, K19 and vimentin are intermediate filament proteins with altered 
expression profiles during tumour development.
METHOD: We have used in vivo and in vitro models to analyse changes in 
intermediate filament proteins. Antibody-based methods were used to study K8 
levels and proteomic analysis to profile the protein content of metastatic 
breast cancer cell variants.
RESULTS: K8 expression declines as human breast tumours progress into an 
invasive phenotype. Analysis of IF proteins indicated altered expression 
profiles of K8, K18, K19 and vimentin, with K8, K18, K19 expressed in high 
levels in the T47D and MCF-7 cell lines, whereas the highly metastatic cell 
lines expressed lower levels of K8 and K18 and no detectable K19. Vimentin 
showed reverse expression profile with T47D and MCF-7 cells having no detectable 
vimentin expression whereas the highly metastatic MDA-MB-231 and MDA-MB-436 
showed high levels. Analysis of acetylation status using specific antibodies 
suggested acetylation occurred within the central coiled domain in the MCF-7 and 
T47D cells. Inhibition of tumour growth by tissue factor (TF) shRNA resulted in 
a dramatic re-elevation of expression of K8 in xenographs of the highly 
metastatic MDA-MB-436 line.
CONCLUSION: Intermediate filament expression alters during epithelial 
mesenchymal transition. Identified post translational modifications may play a 
role in alterations seen in the organisation, solubility and stability of these 
filaments. Epithelial mesenchymal transition can be reversed and an epithelial 
phenotype re-established.