Role of COX-2 in tumorospheres derived from a breast cancer cell line.
BACKGROUND
Cyclooxygenase-2 (COX-2) expression in primary breast cancer predicts tumor cell dissemination to bone marrow, which is a risk factor for recurrence and distant metastasis. "Stem-like" phenotype may be important in cancer metastasis.


METHODS
To investigate the role of COX-2 protein in breast cancer stem-like cells, we analyzed it by co-immunofluorescence in tumorospheres derived from the MCF7 estrogen receptor-positive breast cancer cell line. To evaluate COX-2 function we utilized a COX-2 inhibitor in a clonogenicity assay performed with tumorospheres-derived cells.


RESULTS
We detected rare cells in tumorospheres (one cell per tumorosphere) with very high COX-2 expression (COX-2(high)). COX-2 transfected MCF7 cells were able to generate long-term tumorospheres culture, even though transfection efficiency was only one in a million cells. We detected expression of OCT4 in some COX-2(high) cells, supporting the hypothesis that these cells could be cancer stem-like cells. It is important that COX-2(high) cells showed less expression of Ki-67 than did neighboring cells, indicating that COX-2(high) cells may be progenitors of tumorospheres. Celecoxib inhibited the growth of tumorosphere cultures and the ability of tumorosphere-derived cells to form colonies in vitro, indicating an active role of COX-2 in these processes. However, 2 μM celecoxib failed to eradicate tumorosphere-initiating cells. Finally, we detected rare COX-2(high) cells among SUM149 inflammatory breast cancer cells growing on plastic in serum-containing medium; the SUM149 cell line produces a very high level of COX-2 protein.


CONCLUSIONS
Our results support a role for COX-2 in stem-like breast cancer cells and suggest a mechanism behind a role for COX-2 in disseminated tumor cells, which are known to exhibit characteristic biomarkers and functional properties of stem-like cells.
Singh
Balraj
B
Department of Surgical Oncology and Advanced Research Center for Microscopic Disease, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Cook
Kendra R
KR
Vincent
Laura
L
Hall
Carolyn S
CS
Martin
Cecilia
C
Lucci
Anthony
A
D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology* / Q000503:physiopathology; D000068579:Celecoxib; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D009362:Neoplasm Metastasis / Q000503:physiopathology; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D011960:Receptors, Estrogen / Q000378:metabolism; D013449:Sulfonamides / Q000494:pharmacology
D052246:Cyclooxygenase 2 Inhibitors; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D011720:Pyrazoles; D011960:Receptors, Estrogen; D013449:Sulfonamides; D051546:Cyclooxygenase 2; D000068579:Celecoxib
Annu Rev Med. 2007;58:239-52
17100552
J Biol Chem. 2001 Sep 14;276(37):34975-82
11432874
Nature. 2007 Jun 21;447(7147):1007-11
17581586
Proc Natl Acad Sci U S A. 2003 Apr 1;100(7):3983-8
12629218
Breast Cancer Res Treat. 2009 Sep;117(1):61-8
18663571
J Surg Res. 2006 Apr;131(2):267-75
16457848
Cancer Res. 2008 Jul 15;68(14):5533-9
18632604
J Surg Res. 2006 Jul;134(1):44-51
16678856
Am J Pathol. 2008 Aug;173(2):561-74
18599608
Int J Oncol. 2005 May;26(5):1393-9
15809733
Breast Cancer Res. 2008;10(2):R25
18366788
Breast Cancer Res. 2008;10(1):R10
18241344
Cancer Res. 2005 Jul 1;65(13):5506-11
15994920
Int J Cancer. 2008 Jan 15;122(2):298-304
17935134
J Surg Res. 2008 Jun 15;147(2):240-6
18498876
Oncogene. 2007 May 31;26(26):3789-96
17213821
J Natl Cancer Inst. 2006 Dec 20;98(24):1777-85
17179479
APMIS. 2008 Jul-Aug;116(7-8):754-70
18834417
J Natl Cancer Inst. 2008 May 7;100(9):672-9
18445819
J Biol Chem. 1998 Apr 17;273(16):9886-93
9545330
Cancer Res. 2008 Apr 1;68(7):2419-26
18381450
Cell. 2009 Mar 20;136(6):1136-47
19303855
J Surg Res. 2007 Jun 15;140(2):220-6
17418864
Stem Cells. 2006 Dec;24(12):2685-91
16916925
N Engl J Med. 2005 Aug 25;353(8):793-802
16120859
Int J Mol Med. 2007 Sep;20(3):329-35
17671737
Nat Biotechnol. 2008 Nov;26(11):1269-75
18849973
Stem Cells. 2007 May;25(5):1096-103
17234991
Stem Cells. 2008 Mar;26(3):745-55
18096720
Cancer Cell. 2004 Mar;5(3):263-73
15050918
Cancer Res. 2009 Feb 15;69(4):1302-13
19190339
Science. 1977 Aug 26;197(4306):893-5
887927
Virchows Arch. 2007 Dec;451(6):1039-45
17851687
Clin Cancer Res. 2006 Oct 1;12(19):5615-21
17020963
Nature. 2008 Jul 31;454(7204):646-50
18594515
Genes Dev. 2003 May 15;17(10):1253-70
12756227
J Biol Chem. 2008 Dec 5;283(49):33955-68
18842581