CD44+/CD24- breast cancer cells exhibit enhanced invasive properties: an early step necessary for metastasis.
BACKGROUND
A subpopulation (CD44+/CD24-) of breast cancer cells has been reported to have stem/progenitor cell properties. The aim of this study was to investigate whether this subpopulation of cancer cells has the unique ability to invade, home, and proliferate at sites of metastasis.


METHODS
CD44 and CD24 expression was determined by flow cytometry. Northern blotting was used to determine the expression of proinvasive and 'bone and lung metastasis signature' genes. A matrigel invasion assay and intracardiac inoculation into nude mice were used to evaluate invasion, and homing and proliferation at sites of metastasis, respectively.


RESULTS
Five among 13 breast cancer cell lines examined (MDA-MB-231, MDA-MB-436, Hs578T, SUM1315, and HBL-100) contained a higher percentage (>30%) of CD44+/CD24- cells. Cell lines with high CD44+/CD24- cell numbers express basal/mesenchymal or myoepithelial but not luminal markers. Expression levels of proinvasive genes (IL-1alpha, IL-6, IL-8, and urokinase plasminogen activator [UPA]) were higher in cell lines with a significant CD44+/CD24- population than in other cell lines. Among the CD44+/CD24(-)-positive cell lines, MDA-MB-231 has the unique property of expressing a broad range of genes that favor bone and lung metastasis. Consistent with previous studies in nude mice, cell lines with CD44+/CD24- subpopulation were more invasive than other cell lines. However, only a subset of CD44+/CD24(-)-positive cell lines was able to home and proliferate in lungs.


CONCLUSIONS
Breast cancer cells with CD44+/CD24- subpopulation express higher levels of proinvasive genes and have highly invasive properties. However, this phenotype is not sufficient to predict capacity for pulmonary metastasis.
Sheridan
Carol
C
Department of Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Kishimoto
Hiromitsu
H
Fuchs
Robyn K
RK
Mehrotra
Sanjana
S
Bhat-Nakshatri
Poornima
P
Turner
Charles H
CH
Goulet
Robert
R
Badve
Sunil
S
Nakshatri
Harikrishna
H
D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D051927:CD24 Antigen / Q000235:genetics*; D045744:Cell Line, Tumor; D005260:Female; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics*; D051379:Mice; D009361:Neoplasm Invasiveness / Q000235:genetics; D009362:Neoplasm Metastasis / Q000235:genetics
D051927:CD24 Antigen; D018960:Hyaluronan Receptors