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Mitosis and Cancer
IB Biology
What is cancer videoclip…

http://www.youtube.com/watch?v=LEpTT
olebqo
Cancer is “cells gone wild”!
http://www.youtube.com/watch?v=46Xh7OFkkCE
Cancer

A disease of mitosis

.
The normal “check points” regulating mitosis
are ignored by the cancer cell
Cancer

Begins when a single cell is transformed
from a normal cell to a cancer cell.
Why do normal cells change?
Mutations are random changes to the
base sequence of genes
 Mutagens are agents that cause gene
mutations
 Chemicals and agents that cause cancer
are known as Carcinogens

Why do normal cells change?
Cancer occurs when genes that control
the cell cycle and cell division mutate.
These genes are called oncogenes.
 Mutations in oncogenes results in the
accumulation of cancer cells by
uncontrolled mitosis

Oncogene Example: TP53



TP53 gene encodes for a protein
that acts as a tumour suppressor
This protein plays a critical role
in determining whether DNA
damaged by agents such as
toxic chemicals, radiation, or
ultraviolet (UV) rays will be
repaired or if the damaged cell
will self-destruct (undergo
apoptosis).
Without this protein, DNA
damage accumulates and cells
divide in an uncontrolled way,
leading to a cancerous tumour.
Tumours – Good cells gone bad!
Cancer cells divide (and multiply?) to
form a mass called a tumour.
 As the tumour grows, it releases proteins
from the cell to attract new blood vessel
growth (angiogenesis).

Types of tumours

1. Benign –
Tumour cells remain at original site
(Primary Tumour)
 Unlikely to cause harm

Types of tumours

2. Malignant –
Tumour cell sends signals to produce new
blood vessels at tumour site. This gives
cells their own food and oxygen supply.
 Tumour cells become detached and move
elsewhere to set up a secondary tumour
(Metastasis)

Unusual Features of Cancer Cells

1. “Immortal” – normal cells divide ~50
times then die…cancer cells divide
indefinitely if supplied with nutrients
HeLa cells have
been growing
since 1951!
They are used
in research!
Unusual Features of Cancer Cells

2. Cancer cells do not stop growing
when they contact other cells (unlike
normal cells)– they continue to multiply
and pile up!
Unusual Features of Cancer Cells

3. Cancer cells have abnormal cell
surfaces

Instead of sticking to neighbouring cells,
they tend to break up – this allows tumours
to metastasize (spread)
Unusual Features of Cancer Cells

4. Cancer cells have unusual numbers
of chromosomes or mutations.

Due to:
Aging
 Exposure to toxins (e.g. tobacco tar)
 Mutagens (e.g. uv radiation)
 Normal errors in DNA replication

Treatments

For benign tumours:


Surgery to remove
tumour
Radiation therapy
to destroy
remaining cells at
site of original
tumour
Treatment

For malignant tumours:

Chemotherapy using
drugs to stop cell division.
 Cause cell death in any
dividing cell (especially
cancer cells)
 Also kills cells in
digestive tract, bone
marrow and hair
follicles…
Cigarette

Smoking and cancer: correlation vs
causation
Summary Questions
1. What are oncogenes? Provide an
example
 2. What are mutagens? Provide an
example
 3. What is a mass of cancer cells
called?

Summary Questions
4. What type of tumour remains at its
original location?
 5. What type of tumour can spread due
to new blood vessel production?
 6. What is it called when cancer cells
break away and travel to form new
tumours?

Summary Questions
7. Which cancer treatment destroys
cancer cells at the site of the original
tumour?
 8. Which cancer treatment stops cell
division is all dividing cells including
cancer cells?
