The Hallmarks of Cancer
Hanahan and Weinberg, Cell 144:646 (2011)
Newer Hallmarks of Cancer
Hanahan and Weinberg, Cell 144:646 (2011)
Therapeutic Targeting of the Hallmarks of Cancer
Hanahan and Weinberg, Cell 144:646 (2011)
Cell Regulatory Networks Important in Cancer Cells
Hanahan and Weinberg, Cell 100:57-70 (2000)
Cell Regulatory Networks Important in Cancer Cells
Hanahan and Weinberg, Cell 144:646 (2011)
Cell cycle and its control
Cells must be able to proliferate
- during development
- wound healing
- stem cells in blood, small intestine, immune system
For cells to copy themselves they need to:
- Grow; make more stuff; e.g. proteins, lipids
- Copy their genetic material
- Segregate contents to daughter cells, especially…
- Segregate replicated chromosomes to daughter cells
INTERPHASE:
G1 + S + G2
START
or
Restriction Point
Figure 8.3b The Biology of Cancer (© Garland Science 2007)
Cell Cycle Commandments
A cell resting in quiescence (G0) must not reenter the cycle
unless a proper mitogenic signal is received.
A terminally differentiated cell must not reenter the cycle.
A cell must not start to replicate DNA unless its mass is
sufficient to support cell division.
A cell must replicate every DNA sequence once, and only once,
during each cell division.
If the DNA is damaged, a cell must repair the damage before cell
division.
A cell must not divide until DNA replication has been completed.
Each cell must receive a complete complement of replicated DNA.
The Restriction Point: Integrating GO : NO-GO Signals
Figure 8.6 The Biology of Cancer (© Garland Science 2007)
The Restriction Point: Integrating GO : NO-GO Signals
Figure 8.1 The Biology of Cancer (© Garland Science 2007)
Loss of cell cycle control at the Restriction Point
Two types of genes are mutated in cancer:
G0
proto-oncogenes
M
G2
G1
S
Activity: stimulate cell cycle progression
Mutation in cancer: gain of function
proto-oncogene = wt; oncogene = mutant
Examples: cyclin D1, Mdm2, myc, ras
tumor suppressors
Activity: Inhibit cell cycle progression
Mutation in cancer: loss of function
Examples: Rb, p53, p16, ARF, PTEN
Cell Cycle Checkpoints
The Guardian Mechanisms of
the Genome
THEY ARE DISRUPTED
IN CANCER!
Figure 8.4 The Biology of Cancer (© Garland Science 2007)
S Phase of the Cell Cycle
MCM
Helicase
S Phase of the Cell Cycle
During the S phase, the
duplicated DNA is rearranged
through cohesion to form two
sister-chromatids attached to
each other by cohesins
The cohesins will be removed
during mitosis to allow sisterchromatid separation
Mitosis
Mitosis in Newt
Lung Cells
blue = DNA
green = microtubules
Figure 8.3a The Biology of Cancer (© Garland Science 2007)
At the end of the day:
You need to do metaphase correctly
This requires organizing microtubules….
and attaching them to kinetochores.
Centromere
Kinetochore
Microtubule
Kerry Bloom
Ted Salmon
Microtubule
Kinetochore
The Metaphase to Anaphase Transition:
The key step during mitosis
Metaphase to anaphase transition in a plant cell
INTERPHASE:
G1 + S + G2
START
or
Restriction Point
Figure 8.3b The Biology of Cancer (© Garland Science 2007)
G1-S and G2-M are the major
control points in the cell cycle
1. Fuse M phase cell with interphase
cell: Interphase nucleus enters M
2. Fuse S phase cell with G1 cell:
The G1 nucleus enters S phase
Rao and Johnson
cell fusion experiments
3. Fuse S phase cell with G2 cell:
The G2 nucleus does not enter S
phase
Cyclin Dependent Kinases Regulate the Cell Cycle
Phosphorylation of CDK Targets Changes Their Activity
Now performs
a cell cycle function
Experimental Systems Important for Cell Cycle Studies
Saccharomyces cerevisiae
Schizosaccharomyces pombe
Arbacia punctulata
Xenopus laevis
Budding Yeast Saccharomyces cerevisiae
Budding Yeast: a genetic eukaryotic model organism
Hartwell was interested in the
protein synthesis machinery
Let’s look for mutants that cannot
synthesize proteins
Lee Hartwell
Isolating Temperature Sensitive
Mutants in Haploid Yeast
Serendipity: a scientist’s best friend!
Lee Hartwell
Brian Reid
Brian Reid, an undergrad, needs to look at a microscope
to follow a mutant. They realize that bud size stores
information about the cell cycle
Cdc Mutants Arrest at the Same Cell Cycle Phase
Permissive (low) temperature
Restrictive (high) temperature
The Behavior of a Temperature Sensitive cdc Mutant
cdc mutant growing
at permissive temp (23C)
cdc mutant growth arrested after
6 hrs at non-permissive temp (36C)
How to Clone cdc Genes in Yeast
Cdc Genes Encode Proteins Needed for DNA Replication
Studies in S. cerevisiae
Fission yeast: Schizosaccharomyces pombe
Cdc Genes Encode Proteins Needed for the G2-M Transition:
Studies in S. pombe
Sir Paul Nurse
cdc2+ encodes a kinase
Moreover = cdc28 in S. cerevisiae!
And they can substitute for one another!!!
Cdc2 (fission)
Cdc28 (budding)
START (Restriction Point)
Cdc2 (fission)
Cdc28 (budding)
This is all great and
yeast are really cute and interesting, but
Can we really learn something from all of
this about humans?
Schizosaccharomyces
pombe
Crazy idea
It worked for us with budding yeast
genes. Why not try human genes?
Sir Paul Nurse
Let’s try to complement (rescue)
the cdc2 (-) mutant of pombe with
a human cDNA library
Human cdc2 rescues cdc2 mutants!!
Melanie Lee
Elongated cdc2 mutants,
failing to undergo mitosis
cdc2 mutants,
complemented by a
human cdc2 gene
Summary
- A genetic approach in fission and budding
yeasts reveals genes that are essential in
promoting the cells through the cell cycle
- Key genes encode a protein kinase called CDKs
for Cyclin-Dependent Kinases
CDK1 = the protein encoded by cdc2/CDC28
What about cyclins? How were they discovered?
Woods Hole Marine Biological Laboratory
Tim Hunt
Cyclin was Discovered in Sea Urchin Embryos
can stimulate to
lay lots of eggs
Protein
Level
cyclin A
cyclin B
Time
M
M
M
mitosis
mitosis
mitosis
(Spisula is actually a clam.)
OK, but what does this have to do with CDK’s??
I have the
answer!
Overview of the frog life cycle
OOCYTE GROWS WITHOUT DIVIDING
(MONTHS)
FERTILIZATION
FERTILIZED EGG DIVIDES WITHOUT GROWING
(HOURS)
1 mm
sperm
tadpole feeds, grows
and becomes an adult frog
The Maturation of Frog Eggs
The Maturation of Frog Eggs
An Assay for Maturation Promoting Factor (MPF)
Yoshio Masui, 1971
MPF Activity Peaks Before Each Cell Division
Moreover, MPF has kinase activity
Purification of MPF: The Birth
of Cyclin Dependent Kinases
This is cdc2+!!
(Cdc28 in
S. cerevisiae)
This is cyclin!!
Which = cdc13+
in S. pombe
Phosphorylation of CDK Targets Changes Their Activity
Now performs
a cell cycle function
The Nobel Prize in Physiology or Medicine, 2001
“for their discovery of key regulators of the cell cycle”