Cell Death and Cancer
SNC2D
First a bit more cell division…
How do prokaryotes divide?
 Do all eukaryotes divide their cells using
mitosis?
 Do all cells divide at the same speed?
 What factors affect mitosis?


How do cells die?
1. Binary Fission
◦ Type of cell division used by
prokaryotes (bacteria)
2. Budding

Asexual reproduction in which a new
organism develops from an outgrowth
or bud on another one
3. Regeneration

the process of restoration, and growth
after damage
4. Fragmentation

A form of asexual reproduction
where an organism is split into
fragments and each fragment
develops into mature, fully grown
individuals which are clones of
the original organism

What other factors impact mitosis?
◦ Altitude, antibiotics…
◦ Can you think of any others?
 Chemotherapy
 Radiation
 Sunlight
How do Cells die?
Death due to unexpected and accidental cell
damage.
 This is an unregulated cell death.
 Causes: toxins, radiation, trauma, lack of oxygen
due to the blockage of blood flow.

A cell also dies as a normal part of the
functioning of healthy multicellular organisms.
 This is a regulated, or controlled, cell death of
cells that are no longer useful.
 Apoptosis also removes cells that have lost their
ability to perform efficiently.

Apoptosis

The material of the cell is recycled by the
body.
Comparison
Necrosis
Apoptosis
Pathologic
“Cell Homocide”
Large number of cells
Swelling
Random, diffuse fragmentation
of nucleus
Inflammation
Surrounding normal tissue
damage
Physiologic
“Cell Suicide”
Few cells
Shrinkage
Orderly nuclear condensation
and fragmentation
No inflammation
No secondary tissue damage
Apoptosis Videos
http://www.youtube.com/watch?v=7WRk
Y8q_F3k
 http://www.youtube.com/watch?v=gYWU
TBM8tTo

Cell Lifespans

Cells do not live forever. They can only divide a certain
number of times until they receive a message or instructions
to die. Cell division is necessary for cells to be replaced
after they die.

In your body, 3 billion cells die every minute.

We undergo cell division as part of regeneration, a process
essential for repairing damaged tissue.

Why do we age?
◦ Not entirely sure
◦ as cells die, they are not replaced or just not as quickly. This
results in changes to the structure and function of major body
systems.

What happens when
damage to a cell
impairs its ability to
commit apoptosis and
it divides and divides
and divides?
Cancer
Cancer = uncontrolled cell
division
 Caused by changes in the genes
controlling cell division
 loss of a cell’s ability to undergo
apoptosis (“immortal”)
◦ On/off switch is broken
◦ Continually reproducing
= Tumour
Cancer

In small groups
◦ – Compare Normal Cells to Cancer Cells
Normal Cells
Cancer Cells
Make exact copies of
themselves
through mitosis
Make exact copies of
themselves
through mitosis
Reproduce for about 5060 cell
divisions
Stick together to form
masses of cells as
appropriate
Do not stop reproducing
Self-destruct when too
old or too damaged
May move to another
location of the body
Do not stick to other
cells
Behave independently
Review:
cycle
Review:
TheThe
cellcell
cycle
hashas
fourfour
phases
phases
andcell
controls
cell division
and
controls
division
Two gap or
growth
phases (G1
and G2)
Interphase
S phase DNA
synthesis
M phase Mitosis
Cell Cycle Checkpoints

There are three checkpoints in the
cell cycle
◦ G1-S transition
◦ G2-M transition
◦ Exit M phase transition



Checkpoints are where the cell
assesses whether conditions are
favorable for cell division.
When the environment is not
favorable (for example, when the
cell’s DNA is damaged), a protein
called p53 can stop the cell cycle
and cause the cell to die.
When the proteins that regulate
the cell cycle are mutated or
absent, cells can divide controllably,
leading to cancer.
Tumor suppressors and oncogenes
Mutations in oncogenes and tumor
suppressor genes can lead to cancer
 http://science.education.nih.gov/suppleme
nts/nih1/cancer/activities/activity2_animati
ons.htm

◦ (animation #5)
Cell Cycle Checkpoints

A cell should remain in interphase and
not divide if…
◦ Signals from surrounding cells tell the cell not
to divide
◦ There are not enough nutrients in the cell
◦ The DNA has not yet been replicated
◦ The DNA is damaged

These checkpoints are regulated by
special proteins like p53
Microscopic Appearance of Cancer
Microscopic
Appearance
of
Cancer
Cells
Cells
Definitions
Definitions
 Tumour:
• ◦Tumour:
a mass
of cells resulting
A mass of
cells resulting
from rapidfrom
cell
growth
rapid
cell growth

Benign:
◦ Tumours that stay confined in a small area, causing
little damage

Malignant:
◦ Dangerous tumours that break away and move to
other areas of the body.
• Metastasize
• Spread of
cancer
Cancer Tends to Involve Multiple Mutations
Benign tumor cells
grow only locally and
cannot spread by
invasion or metastasis
Malignant cells invade
neighboring tissues, enter
blood vessels, and metastasize
to different sites
Time
Mutation
inactivates
suppressor
gene
Cells
proliferate
Mutations
inactivate
DNA repair
genes
More mutations,
Proto-oncogenes
mutate to oncogenes more genetic
instability,
metastatic
disease
Causes of Cancer

Mutation:
◦ Random changes that can occur when DNA is
replicated

Carcinogen:
◦ Any environmental factor that can cause a
mutation
Videos on Cancer
http://www.youtube.com/watch?v=j_wRp
a2b5XI
 http://www.youtube.com/watch?v=8n0ijZ
pYXwo
 http://www.pbs.org/wgbh/nova/body/howcancer-grows.html

ANDI – Inserted DNA
Monkey with green glow protein
from a jellyfish inserted into its DNA.
TgCat1 - Green Glow Cats

These GM cats
carry:
◦ Green fluorescent
protein (GFP) gene
◦ and an extra
monkey gene,
called TRIMCyp,
which protects
rhesus macaques
from infection by
feline
immunodeficiency
virus or FIV –
responsible for cat
AIDS
Glow in the dark dog with an
on/off switch!





The switch is a chemical trigger
Give the dog an antibiotic along with food, she’ll start
to glow under UV light
Tegon was cloned and in the process her genes were
modified to instruct her cells to react to an antibiotic
by glowing
This research will help find cures to diseases (like
Alzheimer's and Parkinson's) that are common to both
dogs and humans
Want one?
 She costs $3 million.
Curious Cloning…

Random  In 2008 an American couple
paid more than $150,000 to have their
late pet dog cloned