BIO 203 Lecture Notes - Lecture 18: Natural Killer Cell, Cytotoxic T Cell, Telomerase

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Development of Cancer
DNA damage and cell destruction
Cancer cells do not self-destruct when their DNA is damaged
This makes them difficult to kill with radiation or chemotherapy
Treatments designed to damage DNA of cancer cells and trigger self-
In the lab, most normal human cells divide 50 to 60 times and then enter a
nondividing state called senescence
Telomeres might be the way that a cell “counts” the number of times it has
Pieces of DNA at tips of chromosomes
Made by telomerase, early in development
Most mature cells stop producing telomerase
When DNA is copied for cell division, a tiny piece of every telomere
in the cell is shaved off
Cancer cells do not stop producing telomerase
Telomeres are reconstructed after each cell division
May allow cell division to continue indefinitely
Cancer cells release special growth factors that cause capillaries to invade the
Remove waste
Deliver nutrients
Deliver additional growth factors that spur tumor growth
Serve as routes by which cancer cells can leave the tumor and spread to
other locations
Adherence to neighboring cells
Normal cells
Usually glued in place by cell adhesion molecules (CAMs)
If become “ungluedstop dividing and self-destruct
Cancer cells
Secrete enzymes that break down CAMs, so they are able to break
Continue to divide and evade self-destruction
Body defense cells
Natural killer cells and cytotoxic T cells usually kill cancer cells that
develop in our bodies every day
Some types of cancer cells actively inhibit these defense
Others multiply too quickly for defense cells to destroy them
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