222
Cancer Stem Cells
6.2
Tumor Relapse Might Result from a Failure to Target Cancer
Stem Cells
233
6.3
Cancer Stem Cells Might Be More Resistant to Chemotherapy
234
6.4
Identi±cation of Cancer Stem Cells Might Lead to Better
Drug Selection
234
7
Future Implications of Cancer Stem Cells
235
Bibliography
235
Books and Reviews
235
Primary Literature
236
Keywords
Cancer Stem Cell
A cell within a tumor that possesses the ability to self-renew and is responsible for
maintaining the growth of the tumor; this cell population is the only cell population
within a tumor that has the ability to form a new tumor and can produce progeny of
multiple phenotypes.
Self-renewal
The process by which, upon cell division, at least one of the daughter cells retains the
multipotent capacity of the parent cell.
Tumorigenic Cell
A tumor cell capable of self-renewal and of forming a new tumor.
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Researchers have made stunning advances over the last ±fty years in characterizing
the oncogenic mutations that lead to cancer. However, we are just beginning to
understand the complex consequences of these mutations and how they result in
neoplastic transformation at the cellular level. Most cancers arise in tissues that
contain a stem cell population, such as gut, breast, prostate, lung, and bone marrow.
Stem cells are de±ned by three critical properties: the ability to divide and give rise
to a new stem cell (self-renewal), the ability to give rise to the differentiated cells
of an organ, and the genetic constraints on expansion of the cell population. It is
known that cancer results from the accumulation of mutations in a single target cell,
sometimes over a period of many years. Since stem cells are the only long-lived cells
in most tissues, this suggests that they are the cells in which early mutations leading
to cancer accumulate. Additionally, stem cells are the only normal cells that share
cancer cells’ intrinsic ability to self-renew. Taken together, these two facts suggest
that, in some cases, stem cells may be the target cells for neoplastic transformation.
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