Cell Death and CancerSNC2D

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. BuddingAsexual 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. FragmentationA 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?

NecrosisDeath 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.

How do Cells die?ApoptosisA 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.

ApoptosisThe material of the cell is

recycled by the body.

Comparison

Apoptosis Videoshttp://www.youtube.com/watch?v

=7WRkY8q_F3k

http://www.youtube.com/watch?v=gYWUTBM8tTo

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 Cancer = uncontrolled cell

divisionCaused by changes in the

genes controlling cell divisionloss of a cell’s ability to

undergo apoptosis (“immortal”)◦On/off switch is broken◦Continually reproducing

= Tumour

CancerIn small groups

◦ – Compare Normal Cells to Cancer Cells

Normal Cells Cancer Cells

Make exact copies of themselvesthrough mitosis

Make exact copies of themselvesthrough mitosis

Reproduce for about 50-60 celldivisions

Do not stop reproducing

Stick together to form masses of cells as appropriate

Do not stick to other cellsBehave independently

Self-destruct when too old or too damaged

May move to another location of the body

Review: The cell cycle has four phases and controls cell division

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 oncogenesMutations in oncogenes and

tumor suppressor genes can lead to cancer

http://science.education.nih.gov/supplements/nih1/cancer/activities/activity2_animations.htm◦(animation #5)

Cell Cycle CheckpointsA 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 Cells

DefinitionsTumour:

◦A mass of cells resulting from rapid cell growth

Benign:◦Tumours that stay confined in a small

area, causing little damageMalignant:

◦Dangerous tumours that break away and move to other areas of the body.

• Metastasize• Spread of

cancer

Causes of CancerMutation:

◦Random changes that can occur when DNA is replicated

Carcinogen:◦Any environmental factor that can

cause a mutation

Videos on Cancerhttp://www.youtube.com/watch?v

=j_wRpa2b5XIhttp

://www.youtube.com/watch?v=8n0ijZpYXwo

http://www.pbs.org/wgbh/nova/body/how-cancer-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