Download Cancer - TASIS IB Biology

THE CELL CYCLE AND CANCER
2.5.2: State that tumours (cancers) are the result
of uncontrolled cell division, and that these can
occur in any organ or tissue
Cell division and cancer
Which karyotype is the bladder cancer cell?
This representative karyotype from a human
prostate cancer cell line before injection into
nude mice shows all human chromosomes
with characteristic marker chromosomes
OK…what tells a cell when to divide
(or, indeed, when NOT to divide)?
Cell cycle controls
Cell Cycle Control
Leland Hartwell
Isolated > 100 genes (in
yeast cells) directly
involved in control of the
cell cycle (CDC genes)
Introduced the concept of
‘Checkpoints’: where the
cell cycle stops to check if
DNA has been perfectly
duplicated, cell size is
correct, etc etc…
Cell cycle control
Sir Paul Nurse
Used another yeast cell
(Saccharomyces) to identify
the CDC2 gene (and
subsequently the equivalent
gene in humans, CDK1),
which was THE rate-limiting
step controlling onset of S,
transition from G1 to S and
from G2 to M phase of the
cell cycle
Cell Cycle Control
Tim Hunt
Used sea urchins to
identify control proteins
which were formed and
degraded throughout the
cell cycle (cyclins) and
bind with CDK molecules,
regulating CDK activity
and selecting proteins to
be phosphorylated
OK…what tells a cell when to divide
(or, indeed, when NOT to divide)?
• Let's get some help from the NOBEL
organisation...
• and how about some help from Harvard?
• Animation
What’s the link between control of the
cell cycle and cancer?
• In cancer, parts of chromosomes are lost,
rearranged or unequally distributed between
daughter cells
• This is often due to defective cell cycle control
• Genes for CDK and cyclins can function as
oncogenes
• Increased levels of CDK and cyclins are often
identified in human cancer cells (e.g. skin,
breast)
‘Faulty’ cell division: defective
telomeres
A telomere is the end of a
chromosome. Telomeres are
made of repetitive
sequences of non-coding
DNA that protect the
chromosome from damage.
Each time a cell divides, the
telomeres become shorter.
Eventually, the telomeres
become so short that the
cell can no longer divide.
‘Faulty’ cell division: oncogenes
An oncogene is a mutated
gene that contributes to
the development of a
cancer.
In their normal,
unmutated state,
oncogenes are called
proto-oncogenes, and
they play roles in the
regulation of cell division
Great links on cancer biology
• Cold Harbour website
• Howard Hughes p53 site
School Trip
School Trip
• Swiss Oncology Research Institute