Download The Cell Cycle and Cancer

The Cell Cycle and Cancer
Checkpoints in the Cell Cycle
In normal healthy cells, there are proteins
that send messages to the nucleus to stay
in interphase if:
1. Signals from surrounding cells say to not divide
2. DNA has not been replicated or is damaged on certain
genes
3. Finite number of divisions – cellular apoptosis
1. Chemical Signals from surrounding cells
help tell a cell when to start and stop
dividing.
•
•
There are not enough nutrients to allow proper growth
All cellular space is currently covered – called contact
inhibition, as all cells only grow to a certain density
2. DNA has not been replicated or is damaged
Before a cell divides,
the DNA is checked
to make sure it has
replicated correctly. (If
DNA does not copy
itself correctly, a gene
mutation occurs.
DNA replication animation:click
on DNA picture
Key Gene Mutations
• Oncogenes, mutant alleles of a proto-oncogenes
– Oncogenes encode proteins that stimulate proliferation or
inhibit apoptosis
• Tumor-suppressor genes (TSGs), also called
– “gatekeepers”, which encode for regulators of various cellcycle checkpoints
– “caretakers”, which encode proteins responsible for
detecting and repairing mutations
Cell Cycle Controls
• Timing is controlled by
cyclic variations in the
concentrations of
certain proteins –
cyclins
Checkpoints are
included to stop the
cycle in the event of
catastrophic damage
or incomplete steps.
DNA mutations disrupt the cell cycle.
Mutations may be
caused by:
1. radiation
2. smoking
3. Pollutants
4. chemicals
5. viruses
3. Finite Number of Divisions
The regulated death of a cell that is no longer
useful (e.g. white blood cells post-infection) or
has lost its ability to function efficiently is called
apoptosis.
What happens when damage
to a cell impairs its ability to
commit apoptosis and it
divides and divides and
divides?
You get Cancerous cells
The Beginning of Cancerous Growth
Cancers grow more quickly
where cells divide frequently.
Cancerous growths are called
tumours.
Underlying tissue
Invasion and Metastasis
Cancer cells can invade
surrounding tissues and
blood vessels.
They can also be
transported by the
circulatory system to other
parts of the body
(metastasis).
Cancer cells then
grow at the new
locations.
METASTASIS
The transfer of disease from one
organ
or part of an organ to another not
directly connected with it
Video link below:
https://www.youtube.com/watch?v=rrMq8u
A_6iA&feature=player_embedded
Malignant versus Benign Tumors
Benign tumor cells
grow only locally and
cannot spread by
invasion or metastasis.
Time
Malignant cells
invade neighboring
tissues, enter blood
vessels, and
metastasize to
different sites.
Cancer is a disease of the cell cycle. Some
of the body’s cells divide uncontrollably and
tumors form.
Tumor in Colon
Tumors in Liver
While normal cells will stop dividing if there is a mutation in
the DNA, cancer cells will continue to divide with mutation.
Due to DNA mutations, cancer cells ignore the
chemical signals that start and stop the cell cycle.
They also no longer communicate well with
neighboring cells
Differences between Benign and
Malignant tumors
BENIGN
1.Often encapsulated
2.Well differentiated
3.Low mitotic rate
4.Noninvasive
5.Non-metastasising
MALIGNANT
Non encapsulated
Poorly differentiated
High mitotic rate
Invasive
Metastasising
Why Cancer Is Dangerous
Melanoma (skin cancer)
cells can travel through
the circulatory system.
Liver
Melanoma
(initial tumor)
The cancer that
spreads to the liver
would be called
metastatic melanoma,
not liver cancer.
Cervical Cancer Screening
Normal
Pap smear
But even earlier
Normal
Pap smear
stages of cancer
can be detected
by screening
cells.
Abnormal
Pap smear
Abnormal
Pap smear
Biopsies similarly
look at cells
inside suspected
tumours.
Cancer Cells Look Different
SUMMARY
Normal Cell Division
1. DNA is replicated
properly.
2. Chemical signals start
and stop the cell cycle.
3. Cells communicate with
each other so they
don’t become
overcrowded.
Cancer Cells
1. Mutations occur in the
DNA when it is
replicated.
2. Chemical signals that
start and stop the cell
cycle are ignored.
3. Cells do not communicate
with each other and
tumors form.
Apoptosis
The material of the cell is recycled by the body.