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Hanahan and Weinberg, Cell 144:646 (2011)
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
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
Figure 8.3b The Biology of Cancer (© Garland Science 2007)
STARTor
Restriction Point
INTERPHASE:G1 + S + G2
Cell Cell CCycle ycle CommandmentsCommandments
A cell must replicate A cell must replicate every DNA sequence once, and only once, every DNA sequence once, and only once, during each cell division.during each cell division.
A cell must not start to replicate DNA unless its mass is sufficieA cell must not start to replicate DNA unless its mass is sufficient to support nt to support cell division.cell division.
If If the DNA is damaged, a cell must repair the damage before cell the DNA is damaged, a cell must repair the damage before cell division.division.
A cell must not divide until DNA replication has been completed.A cell must not divide until DNA replication has been completed.
Each cell must receive a complete complement of replicated DNA.Each cell must receive a complete complement of replicated DNA.
A cell resting in quiescence (GA cell resting in quiescence (G00) must not reenter the cycle u) must not reenter the cycle u
nless a proper mitogenic signal is receivednless a proper mitogenic signal is received..
A terminalA terminally differentiated cell must not reenter the cycle.ly differentiated cell must not reenter the cycle.
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)
The Restriction Point: Integrating GO : NO-GO Signals
Two Two types types of genes are mutated in cancerof genes are mutated in cancer::
Loss of cell cycle control at the Restriction PointLoss of cell cycle control at the Restriction Point
tumor suppressorstumor suppressors
proto-oncogenesproto-oncogenesActivity: stimulate cell cycle progression
Mutation in cancer: gain of functionproto-oncogene = wt; oncogene = mutant
Examples: cyclin D1, Mdm2, myc, ras
Activity: Inhibit cell cycle progressionMutation in cancer: loss of functionExamples: Rb, p53, p16, ARF, PTEN
GG00
MM
G2G2
SS
G1G1
Figure 8.4 The Biology of Cancer (© Garland Science 2007)
Cell Cycle CheckpointsThe Guardian Mechanisms of
the Genome
THEY ARE DISRUPTED IN CANCER!
S Phase of the Cell Cycle
MCMHelicase
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 sister-chromatid separation
S Phase of the Cell Cycle
Mitosis
Figure 8.3a The Biology of Cancer (© Garland Science 2007)
Mitosis in NewtLung Cells
blue = DNAgreen = microtubules
At the end of the day:You need to do metaphase correctly
This requires organizing microtubules….
Kerry Bloom
Kinetochore
Microtubule
Microtubule
KinetochoreCentromere
Ted Salmon
and attaching them to kinetochores.
The Metaphase to Anaphase Transition:The key step during mitosis
Metaphase to anaphase transition in a plant cell
Figure 8.3b The Biology of Cancer (© Garland Science 2007)
STARTor
Restriction Point
INTERPHASE:G1 + S + G2
G1-S and G2-M are the major control points in the cell cycle
Rao and Johnsoncell fusion experiments
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
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 performsa cell cycle function
Experimental Systems Important for Cell Cycle Studies
Arbacia punctulata
Xenopus laevisSchizosaccharomyces pombe
Saccharomyces cerevisiae
Budding Yeast Saccharomyces cerevisiae
Lee Hartwell
Hartwell was interested in the protein synthesis machinery
Budding Yeast: a genetic eukaryotic model organism
Let’s look for mutants that cannot synthesize proteins
Isolating Temperature Sensitive Mutants in Haploid Yeast
Lee Hartwell
Serendipity: a scientist’s best friend!
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
Brian Reid
Permissive (low) temperature Restrictive (high) temperature
Cdc Mutants Arrest at the Same Cell Cycle Phase
cdc mutant growingat permissive temp (23C)
cdc mutant growth arrested after 6 hrs at non-permissive temp (36C)
The Behavior of a Temperature Sensitive cdc Mutant
How to Clone cdc Genes in Yeast
Cdc Genes Encode Proteins Needed for DNA ReplicationStudies in S. cerevisiae
Fission yeast: Schizosaccharomyces pombe
Cdc Genes Encode Proteins Needed for the G2-M Transition:Studies in S. pombe
cdc2+ encodes a kinase Moreover = cdc28 in S. cerevisiae!
And they can substitute for one another!!!
Sir Paul Nurse
START (Restriction Point)Cdc2 (fission)
Cdc28 (budding)
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
Sir Paul Nurse
Crazy idea
Let’s try to complement (rescue) the cdc2 (-) mutant of pombe with a human cDNA library
It worked for us with budding yeast genes. Why not try human genes?
Human cdc2 rescues cdc2 mutants!!
Elongated cdc2 mutants, failing to undergo mitosis
cdc2 mutants, complemented by a
human cdc2 gene
Melanie Lee
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?
Tim Hunt
Woods Hole Marine Biological Laboratory
Cyclin was Discovered in Sea Urchin Embryos
ProteinLevel
Time
cyclin A cyclin B
M M M
can stimulate to
lay lots of eggs
mitosis mitosis mitosis
(Spisula is actually a clam.)
OK, but what does this have to do with CDK’s??
I have theanswer!
Overview of the frog life cycle
1 mm
spermtadpole feeds, grows
and becomes an adult frog
OOCYTE GROWS WITHOUT DIVIDING(MONTHS) FERTILIZATION
FERTILIZED EGG DIVIDES WITHOUT GROWING(HOURS)
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 Birthof 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 performsa cell cycle function
The Nobel Prize in Physiology or Medicine, 2001
“for their discovery of key regulators of the cell cycle”