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Molecular and Cellular Biology, October 2001, p. 6529-6536, Vol. 21, No. 19
Department of Genetics, Howard Hughes Medical
Institute, Harvard Medical School, Boston, Massachusetts 02115
Received 27 March 2001/Returned for modification 11 June
2001/Accepted 2 July 2001
Many tumor cells are impaired in adhesion-regulated apoptosis,
which contributes to their metastatic potential. However, suppression of this apoptotic pathway in untransformed cells is not mediated only
by adhesion to the extracellular matrix but also through the resulting
ability to spread and adopt a distinct morphology. Since cell spreading
is dependent on the integrity of the actin microfilament cytoskeleton,
we sought to determine if actin depolymerization was sufficient to
induce apoptosis, even in the presence of continuous attachment. For
this study, we used a human mammary epithelial cell line (MCF10A),
which is immortalized but remains adhesion dependent for survival.
Treatment of MCF10A cells with latrunculin-A (LA), an inhibitor of
actin polymerization, rapidly led to disruption of the actin
cytoskeleton and caused cell rounding but preserved attachment.
Initiation of apoptosis in LA-treated MCF10A cells was detected by
mitochondrial localization of the Bax apoptotic protein, which was
prevented by overexpression of Bcl-2. DNA fragmentation and
poly(ADP-ribose) polymerase (PARP) cleavage in LA-treated MCF10A cells
indicated progression to the execution phase of apoptosis. The
MDA-MB-453 cell line, which was derived from a metastatic human mammary
tumor, was resistant to PARP cleavage and loss of viability in response
to actin depolymerization. Stable overexpression of Bcl-2 in the
untransformed MCF10A cells was able to recapitulate the resistance to
apoptosis found in the tumor cell line. We demonstrate that inhibition
of actin polymerization is sufficient to stimulate apoptosis in
attached MCF10A cells, and we present a novel role for Bcl-2 in cell
death induced by direct disruption of the actin cytoskeleton.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.19.6529-6536.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Human MCF10A Mammary Epithelial Cells Undergo Apoptosis following
Actin Depolymerization That Is Independent of Attachment and
Rescued by Bcl-2
*
Corresponding author. Mailing address: Department of
Genetics, Howard Hughes Medical Institute, Harvard Medical School,
Warren Alpert Bldg., Rm 539, 200 Longwood Ave., Boston, MA 02115. Phone: (617) 432-7667. Fax: (617) 432-7944. E-mail:
leder{at}rascal.med.harvard.edu.
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