Cancer exploits the body's wound-healing
process, study finds
CAMBRIDGE, Mass. (May 5, 2005) — Scientists have
known for the last decade that a link exists between
wound healing and cancer. For instance, in a 1994 experiment
at the Lawrence Berkeley National Laboratory, chickens
infected with a cancer virus developed tumors in areas
of their body that had undergone wounding or scarring,
while no tumors developed in infected areas that had
not suffered wounding. However, the biological mechanism
for this process hasn’t been clear.
Now, through studying muscle tissue in breast cancer,
scientists in the lab of Whitehead Institute Member
Robert Weinberg
have discovered the process by which tumors hijack normal
wound-healing processes and use them for their own purposes.
Reported in the May 6 issue of the journal Cell, the
research began when Akira Orimo, a postdoctoral scientist
in Weinberg’s lab, investigated the nature of
stromal cells found in breast cancer tumors. Stromal
cells form the connective tissue in a mammal’s
organs and glands. They also form the connective tissue
inside a tumor. Tumors are composed mostly of cancer
cells and stromal cells, and researchers have wondered
if the stromal cells in tumors function any differently
than they do in normal tissues. Do they simply hold
the tumor together the same way they hold a pancreas
or a liver together, or do they actively work with the
cancer cells in promoting the tumor’s growth?
“It turns out the cancer cells are not acting
alone,” says Weinberg, who is also a professor
of biology at MIT. “These stromal cells play an
important role in helping these cells, and therefore
tumors, to grow.”
Orimo found that a particular protein produced by the
stromal cells and recruited into human breast cancers,
called SDF-1, is a key player in helping tumors grow.
SDF-1 interacts with a class of cells called endothelial
precursor cells. Found primarily in the blood, these
cells travel throughout the body and help aid wounded
tissue by enabling new blood vessels to form, a process
called angiogenesis. They are an integral part of the
body’s ability to heal itself.
The stromal cells in the breast cancer tumor produce
SDF-1, which in turn persuades these endothelial precursor
cells to enter the tumor. Once they do, they help the
tumor to form its own robust network of blood vessels,
weaving a circulatory system throughout the tumor mass.
The tumor can now access the nutrients present in the
host’s circulating blood and can then grow unchecked.
“Essentially, these stromal cells opportunistically
exploit the normal wound healing process to benefit
the tumor,” says Weinberg.
In recent years, scientists have focused on angiogenesis
as a target for therapeutics, with some success. “These
findings are one part of the larger angiogenesis picture,”
says Weinberg. “They lend precision and specificity
to that overall scheme.”
Orimo now plans to further investigate this process
by disturbing the interactions between the stromal cells
and the cancer cells, work that may yield new therapeutic
insights.
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