Changes in cytoskeletal protein composition indicative of an epithelial-mesenchymal transition in human micrometastatic and primary breast carcinoma cells.
OBJECTIVE
The bone marrow is a frequent and clinically important homing site for early disseminated breast cancer cells. Here, we aimed to profile the protein expression of these cells using unique cell line models and to evaluate the prognostic relevance of candidate gene expression for breast cancer patients.


METHODS
To identify expression patterns characteristic for micrometastatic cells, three different cell lines (BC-K1, BC-P1, and BC-S1) established by SV40 immortalization of cancer cells isolated from the bone marrow of patients with breast cancer were compared with MCF-7 breast cancer and SV40 immortalized normal breast ductal cells (MTSV-1.7) using two-dimensional gel electrophoresis followed by MALDI-ToF analysis. The prognostic significance and clinicopathologic associations of selected differentially expressed proteins were evaluated using high-density breast cancer tissue microarrays.


RESULTS
In contrast to MCF-7 and MTSV1-7 reference cell lines, all micrometastatic cancer cell lines displayed loss of epithelial cytokeratins (CK8, CK18, and CK19) and ectopic expression of vimentin commonly present in mesenchymal cells. Immunohistochemical analysis of 2,517 samples of breast cancer further showed that loss of cytokeratin and ectopic vimentin expression were significantly associated with a higher tumor grade, high mitotic index, and negative estrogen/progesterone-receptor status. Although in univariate analyses significantly related to clinical outcome, none of the cytokeratins analyzed were independently associated with either overall or cancer-specific survival.


CONCLUSIONS
Micrometastatic cancer cells exhibit marked changes in the expression pattern of cytoskeletal proteins indicative of an epithelial-mesenchymal transition. This phenotypical change could already be detected in primary tumors and is associated with the aggressive behavior of breast cancer cells in vivo.
Willipinski-Stapelfeldt
Birthe
B
Institute of Tumor Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Riethdorf
Sabine
S
Assmann
Volker
V
Woelfle
Ute
U
Rau
Thomas
T
Sauter
Guido
G
Heukeshoven
Jochen
J
Pantel
Klaus
K
D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000032:analysis*; D015180:Electrophoresis, Gel, Two-Dimensional; D004848:Epithelium / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007381:Intermediate Filament Proteins / Q000032:analysis; D007633:Keratins / Q000032:analysis; D008648:Mesoderm / Q000378:metabolism / Q000473:pathology*; D015999:Multivariate Analysis; D009362:Neoplasm Metastasis / Q000473:pathology; D011379:Prognosis; D020543:Proteome / Q000032:analysis; D040901:Proteomics / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D016019:Survival Analysis; D046888:Tissue Array Analysis / Q000379:methods; D014746:Vimentin / Q000032:analysis
D003598:Cytoskeletal Proteins; D007381:Intermediate Filament Proteins; D020543:Proteome; D014746:Vimentin; D007633:Keratins