Changes in keratin expression during metastatic progression of breast cancer: impact on the detection of circulating tumor cells.
OBJECTIVE
Circulating tumor cells (CTC) might function as early markers for breast cancer metastasis or monitoring therapy efficacy. Enrichment and identification of CTCs are based on epithelial markers that might be modulated during epithelial-mesenchymal transition. Little is known about the expression of keratins in CTCs and whether all CTCs can be detected with antibodies directed against a limited panel of keratins.


METHODS
Protein expression of keratin 2, 4-10, 13-16, 18, and 19 were assessed by a cocktail of antibodies (C11, AE1, AE3, and K7) and keratin antibodies C11 and A45-B/B3 alone in 11 breast cancer cell lines and 50 primary breast carcinomas and their lymph node metastases. Furthermore, CTCs were assessed in blood of 70 metastatic breast cancer patients.


RESULTS
Claudin-low cell lines did not show expression of normal breast epithelial keratins but were positive for K14 and K16, detected by the cocktail only. Primary breast carcinomas showed changes in keratin expression during metastatic progression to the lymph nodes. In 35 of 70 patients CTCs were identified, of which 83%, 40%, and 57% were identified by the cocktail, C11 and A45-B/B3, respectively. Identification of CTCs by the cocktail was associated with shorter survival (P < 0.01). In silico analyses revealed association between KRT16 expression and shorter relapse-free survival in metastatic breast cancer.


CONCLUSIONS
Breast cancer cells show a complex pattern of keratin expression with potential biologic relevance. Individual keratin antibodies recognizing only a limited set of keratins inherit the risk to miss biologically relevant CTCs in cancer patients, and antibody cocktails including these keratins are therefore recommended.
Department of Tumor Biology, Center of Experimental Medicine, and Department of Gynecology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Simon A
SA
Joosse
Juliane
J
Hannemann
Julia
J
Spötter
Andreas
A
Bauche
Antje
A
Andreas
Volkmar
V
Müller
Klaus
K
Pantel
D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000401:mortality / Q000473:pathology*; D045744:Cell Line, Tumor; D018450:Disease Progression; D005260:Female; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D053536:Keratin-16 / Q000235:genetics / Q000378:metabolism; D007633:Keratins / Q000235:genetics / Q000378:metabolism*; D008207:Lymphatic Metastasis; D009360:Neoplastic Cells, Circulating / Q000378:metabolism*; D016019:Survival Analysis
D053536:Keratin-16; D007633:Keratins