Neoplasma Vol.52, p.435-440, 2005
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Title: Cancer stem cells
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Author: A., SOLTYSOVA
; V., ALTANEROVA
; C., ALTANER
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Abstract: There is an increasing evidence supporting the cancer stem cell
hypothesis. Normal stem cells in the adult organism are
responsible for tissue renewal and repair of aged or damaged
tissue. A substantial characteristic of stem cells is their ability
for self-renewal without loss of proliferation capacity with each
cell division. The stem cells are immortal, and rather resistant
to action of drugs. They are able to differentiate and form
specific types of tissue due to the influence of
microenvironmental and some other factors. Stem cells divide
asymmetrically producing two daughter cells – one is a new
stem cell and the second is progenitor cell, which has the ability
for differentiation and proliferation, but not the capability
for self-renewal. Cancer stem cells are in many aspects similar to
the stem cells. It has been proven that tumor cells are
heterogeneous
comprising rare tumor initiating cells and abundant non-tumor
initiating cells. Tumor initiating cells – cancer stem
cells have the ability of self-renewal and proliferation, are
resistant to drugs, and express typical markers of stem cells. It
is
not clear whether cancer stem cells originate from normal stem
cells in consequence of genetic and epigenetic changes
and/or by redifferentiation from somatic tumor cells to the stem-
like cells. Probably both mechanisms are involved in the origin
of cancer stem cells. Dysregulation of stem cell self-renewal is a
likely requirement for the development of cancer. Isolation
and identification of cancer stem cells in human tumors and in
tumor cell lines has been successful. To date, the existence
of cancer stem cells has been proven in acute and chronic myeloid
leukemia, in breast cancer, in brain tumors, in lung
cancer and gastrointestinal tumors.
Cancer stem cell model is also consistent with some clinical
observations. Although standard chemotherapy kills most
cells in a tumor, cancer stem cells remain viable. Despite the
small number of such cells, they might be the cause of tumor
reccurrence, sometimes many years after the "successful" treatment
of primary tumor. Growth of metastases in distinct areas
of body and their cellular heterogeneity might be consequence of
cancer stem cell differentiation and/or dedifferentiation
and asymmetric division of cancer stem cells. Further
characterization of cancer stem cells is needed in order to
find ways to destroy them, which might contribute significantly to
the therapeutic management of malignant tumors.
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Keywords: stem cells, progenitors, mutation, cancer stem cells,
differentiation, redifferentiation, resistance, therapy
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Year: 2005, Volume: 52, Issue: |
Page From: 435, Page To: 440 |
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