Biomedical Engineering Reference
In-Depth Information
2 .
Cancer stem cells
. Finding cancers' stem cells is a rapidly growing area of
research. These cancer-causing cells, which make up a tiny fraction of cells
within tumors, according to research data have properties similar to those of
normal stem cells and are considered arising from them (
3
) . However, cancer
stem cells make up only a tiny number of the total cancer cells in a leukemia
patient, which makes the cells next to impossible to find (
4
) . Therefore, it seems
that promise of this line of research can only be realized by studying adult stem
cells as well as embryonic stem cells (ESCs). The latter are, as we know, still
ethical problem and therefore substantially controversial because an early embryo
is destroyed when researchers remove stem cells from it. While in many studies
volunteers could provide samples, that will not be the case for all types of dis-
eases; an alternative is to take the stem cells from embryos that carry a genetic
defect for specific diseases and grow them in a larger number as it was done with
patients with chronic myelogenous leukemia (CML) by Weinberg et al. (
4
) .
Researchers have traditionally thought of cancer as a collection of cells, all grow-
ing exponentially. Weinberg et al. demonstrated convincingly in their study that
the model is wrong, since only a few cells were endowed with the ability to rep-
licate (
4
). It has profound implications for how we think tumors evolve and how
we treat tumors. So, conventional cancer therapies do an effective job, killing the
majority of cells within the tumor, but they may miss cancer stem cells, accord-
ing to this new research. As a result, cancers often recur (
4-
7
) . The reason is
(among others) in the fact that clinicians are reinjecting also cancer cells with
healthy stem cells during reinfusion after aphaeresis collection. They accumulate
and renew with a time to the critical level causing relapse or death.
Types of Stem Cells According to the Available Sources
for the Application in Clinical Arena
(1)
Embryonic stem cells
, (2)
Fetal stem cells
, (3)
Cord blood stem cells, and
(4)
Adult stem cells of bone marrow and different tissues and organs
within an adult
organism
Therapeutic Application of Each Particular Type of Stem Cells:
Advantages and Limitations
1 .
Embryonic stem cells: from therapeutic cloning to stembrids, and back, around
the world
In 2004 and 2005, South Korean team announced the use of therapeutic cloning
to create human ESCs that were genetically and therefore immunologically
matched to specific people (the critical issue that we really wish to overcome in
