Normal Cell Vs. Tumor Cell
Tumor cells vary from
normal cells in several basic ways. First, the division of
normal cells is tightly regulated by special cell signals.
With tumor cells, it’s as if the signals are no longer
produced or perhaps they are no longer received.
Research involving cells is often accomplished by
removing the cells from an individual and growing them in a
sterile dish with the nutrients required for their survival.
Growing cells for research use is termed “cell culture”.
Just by watching normal cells in cell culture it is obvious
that their division is regulated by something. Normal cells
in culture grow until the bottom of their dish is carpeted
with the cell. The layer is only 1 cell thick. Once this
density is reached, they stop dividing because there is no
more space. If one cell dies, an adjacent one will divide to
fill in the space. Additionally, normal cells will divide a
certain number of times after which time, the division
process halts. There are a certain pre-determined number of
generations that may be produced and then there is no more
dividing. Eventually, the entire culture will die.
With tumor cells, it’s a completely different story.
Tumor cells will divide over and over, time after time;
forever if supplied with nutrients. With enough time, tumor
cells in culture will become a piled up mess. They lack
order to their growth. It is as though tumor cells lose have
lost the capacity to follow the rules and they divide
(proliferate) out of control.
A second major difference between normal cells and tumor
cells is that normal cells perform a special function or
duty for the body. Healthy cells have specialized behaviors
and serve a purpose. For example, lung cells have a
specialized duty to perform while cells of cardiac tissue
have a very different one. Normal cells taken from different
tissues even have very different appearances. Tumor cells
have a different appearance than normal cells taken from the
tissue they are derived from. This is due to the fact that
they have lost their specialized function.
Differentiation is the term given to describe the
specialized function a given cell has. Differentiation and
proliferation are closely tied together. In general, a cell
that proliferates at a high rate loses some of its
specialized function. The problem is, it really doesn't have
time to perform a specific function since its too busy
dividing. Cells that perform a highly specific function
(i.e. differentiated) have a lower rate of proliferation.
Researchers are studying the possibility of making
tumor/cancer cells differentiated so they might lose their
ability to proliferate continuously. In theory, this would
cause the tumor to stop growing.
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