Transcript Cancer, Aging and Telomeres

Cancer, Aging and
Telomeres
How molecular genetic research
contributes to a better
understanding of cancer and
aging in humans
What is cancer?
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Cancer is the result of accelerated growth of
undifferentiated cells
Proto-oncogenes in cells regulate mitosis, cell
growth and apoptosis
Apoptosis – cells are programmed to self
destruct once they become damaged or old
Oncogenes are mutated proto-oncogenes that
cause uncontrolled growth and result in tumors
Normal Cell Growth
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Mitosis is tightly controlled by enzymes and feedback
mechanisms
Membrane proteins signal contact – this “contact
inhibition” halts cell division (growth and replication)
Proto - oncogenes to oncogenes
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Cells also have proteins
that recognize cells from
the wrong part of the
body and destroy them
(apoptosis)
Cells that are damaged
self destruct (apoptosis)
Mutations in any
protooncogenes can
result in oncogenes that
do not initiate apoptosis
Epidermal Growth Factor Receptor
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Example: Epidermal
Growth Factor Receptor
Normally, a molecule
activates the receptor and
the cell begins mitosis
A mutation in the ECF
receptor that no longer
requires an activator,
means that cell continues
to divide indefinitely
The Immortal cells of Henrietta Lacks
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Henrietta Lacks' cells were essential in developing the polio vaccine and were used in
scientific landmarks such as cloning, gene mapping and in vitro fertilization.
Courtesy of the Lacks family
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Read more: http://www.smithsonianmag.com/science-nature/Henrietta-Lacks-ImmortalCells.html#ixzz1LDFqjFDb
HeLa Cells
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Henrietta Lack’s cells were taken
from a biopsy sample of a cervical
cancer tumor in 1951
They were used to develop an
immortal line of human cells, that
could divide indefinitely, be split
into batches and given to different
researchers
All vaccine development and
many drug tests can only be done
on human tissue cultures
Read more in The Immortal Life of
Henrietta Lacks by Rebecca
Skloot
Telomeres
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Telomeres are made of short subunits that
extend the length of a chromosome
DNA polymerase can not replicate and entire
chromosome – some information at the end is
lost as the enzyme detaches
TTAGGG that repeats about 2 000 times in
human skin cells is an example of a telomere
They are found at the end of linear
chromosomes
Telomerase is an enzyme that adds telomeres
Telomeres and Protoists
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Single celled
eukaryotes contain
large amounts of
telomerase that add
telomeric sequences
after DNA cell division
This makes them
immortal – like this
amoeba
Telomerase
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Adult stem cells in bone marrow
that produce blood cells contain
telomerase so there is no limit to
their cell divisions
Telomerase has also been found
in certain cancerous tumors and
has been shown to induce tumors
when introduced into healthy
tissue
Shortening telomeres eventually
leads to DNA polymerases
clipping off the ends of genes
during replication and is thought to
contribute to aging