Some stem cells can trigger tumors June 5, 2012 By Anne Ju in CancerTumor size
and collagen fiber alignment in the absence (left) and presence (right) of
adipose stem cells. (Fischbach lab)(Medical Xpress) -- Stem cells often used in
reconstructive surgery following mastectomies and other cancer-removal
treatments may pose a danger: Cornell biomedical scientists have discovered
that these cells, in contact with even trace amounts of cancer cells, can
create a microenvironment suitable for more tumors to grow."It is
necessary for us not only to think about what happens with these cells in an
otherwise healthy patient, but also, what the fate of stem cells may be in a
patient who is prone to disease," said Claudia Fischbach-Teschl, assistant
professor of biomedical engineering, who led the research published in
Proceedings of the National Academy of Sciences, June 4.The cells the
researchers studied are derived from fat and are called adipose-derived stem
cells. They are useful for tissue engineering and reconstructive surgery
because they are good at taking over healthy tissue function and recruiting new
blood vessels to promote healing.But they might be too good -- that is, the
Cornell researchers observed that the presence of cancer cell media -- the
soluble material that contains chemicals secreted by tumor cells -- prevents
the stem cells from turning into fat cells as would be desired. Instead, they triggered
the cells to secrete chemicals known as "factors" that promote blood
vessel growth, or angiogenesis, and to develop into myofibroblasts, which are
cells known to play a role in tumor development.These alterations led to a
stiffening of the extracellular matrix that surrounds the cells -- the
stiffening is a characteristic feature of breast cancer (which is why tumors
can be palpated). Myofibroblasts make the surrounding tissue more rigid, and
this stiffness triggers more changes in the stem cell behavior that lead to
even more tumor-promoting characteristics -- a positive feedback loop.The
researchers observed these changes in in vitro experiments using stem cells and
breast cancer cell lines that varied in aggression. First they collected
soluble media from tumor cells and observed how the stem cells changed in
response. They found that TGF-beta and interleukin-8 are specific
tumor-secreted factors that contribute to the stem cells' eventual change in
phenotype to myofibroblasts. They confirmed their results with in vivo
experiments by injecting stem cells and tumor cells into the mammary glands of
mice.The experimental results are also supported by the fact that obese women
are more likely to develop breast cancer. The presence of more adipose tissue
means larger numbers of adipose stem cells, and one could hypothesize that the
larger stem cell pool could promote tumor-progression processes,
Fischbach-Teschl said.The paper, whose first authors are graduate students
Emily Chandler and Bo Ri Seo, resulted from a multidisciplinary collaboration
that included researchers from the College
of Engineering , College
of Veterinary Medicine and College of Arts Cornell Center
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