Transcript Abl powerpoint

Leukemia is characterized by
hyperproliferation
of immature white blood cells
normal person
Leukemic patient
red
blood
cells
white
blood cell
hyperproliferation
of white blood cells
To understand leukemia we need to examine
development of the Hematopoietic System
self renewal
myeloid
lymphoid
self renewal
self renewal
granulocytes
Wikipedia
Different types of leukemia
affect different stem cell types
and distinct stages in
their development
Molecular Cell Biology
Lodish et al. Fig. 24.1
Chronic myelogenous leukemia (CML)
Annual incidence: 1/100,000 people
(~15% of all leukemias)
Median age: 30-60 yrs
Median survival:
4 yrs with conventional chemotherapy
6 yrs with aIFN therapy;
allogeneic bone marrow transplantation
may cure the patient
Chronic myelogenous leukemia (CML)
Arises in a particular bone marrow stem cell =
The granulocyte precursor
Gives rise to neutrophils , basophils & megakaryocytes.
Neutrophils-- fight infection by phagocytosis
Basophils-- release immune modulators, e.g., histamines, Prostaglandins
Platelets- cell fragments of megakaryocytes.
CML arises in a stem cell that is
a granulocyte precursor
Molecular Cell Biology
Lodish et al. Fig. 24.1
1960 Nowell and Hungerford find that one copy of
chromosome 22 is extremely short in CML patients
Peter Nowell
“The findings suggest a causal relationship between the chromosome
abnormality observed and chronic granulocytic leukemia.”
Nature 1973 243:290-3
“A new consistent
chromosomal
abnormality in
CML identified by
quinacrine fluorescence
and Giemsa staining.”
Rowley JD.
Janet Rowley in 1998
Upon receiving the Lasker Award
A chromosomal translocation
triggers CML
Normal individual
Leukemic patient
Chr. 22
Chr. 9
9; 22 Translocation
The Philadelphia
chromosome
A characteristic karyotype indicates CML
Karyotype courtesy of
L. J. Beauregard,
Eastern Maine Medical Center
Acute lymphoblastic leukemia (ALL)
Affects precursor of leukocytes
(B and T cells)
Ph+ chromosomes in 20% of adult ALL
2-5% of childhood ALL
In adults prognosis very poor
(Only 35- 40% of adults with ALL survive 2 years)
Bone marrow transplant
the only long term treatment
Chromosomal rearrangements are a hallmark of leukemia,
being present in 70-90% of cases
Table 4.5 The Biology of Cancer (© Garland Science 2007)
Why is this the case?
Table 4.5 The Biology of Cancer (© Garland Science 2007)
We cannot dedicate all 25,000
genes in the genome
just to make antibodies.
What’s the solution?
Put antibodies together
by a mix-and match approach!
Molecular Biology of the Cell Alberts et al
requires rearranging the DNA
Molecular Biology of the Cell Alberts et al
requires rearranging the DNA
Molecular Biology of the Cell Alberts et al
The result:
an antibody
light chain
Molecular Biology of the Cell Alberts et al
Since there are multiple types of each
gene segment, there are thousands of
possible V-D-J combinations
Each B cell gets a unique combination
Since there are multiple types of each
gene segment, there are thousands of
possible V-D-J combinations
Each B cell gets a unique combination
As we have seen, sometimes this goes wrong,
and other genes are juxtaposed to the Ig or TCR genes
Rearrangement mistakes can also juxtapose
Other genes with oncogenic consequences
The Philadelphia chromosome
translocation fuses
the bcr and abl genes
normal individual
Leukemic patient
bcr
abl
Bcr-abl
Chr. 22
Chr. 9
De Klein et al. Nature 300, 765 (1982)
Groffen et al. Cell 36, 93 (1984)
9; 22 Translocation
fuses Bcr and Abl
Abelson was first identified as the oncogene
carried by Abelson leukemia virus,
which causes pre-B cell Lymphoma in mice
Abelson and Rabstein, Cancer Res 30, 2213 (1970)
The v-abl containing
retrovirus was recovered
from a tumor found
in mice infected by
Moloney Leukemia virus
In CML the translocation results in production
of a fusion protein that joins
the amino-terminal end of the BCR protein
to most of the Abl protein
The Cell, G. Cooper, Fig. 15.25
In fact, different breakpoints in bcr
Lead to slightly different Bcr-Abl fusion proteins
That are found in different cancers
Fluorescence In Situ Hybridization (FISH)
a tool for diagnosing CML
abl
bcr
Fluorescence In Situ Hybridization (FISH)
a tool for diagnosing CML
fusion 22
bcr/abl
fusion 9
abl/bcr
abl
bcr
The current methd: PCR
BCR
ABL
Abelson kinase
• A fatty-acid modified and actin-binding
non-receptor tyrosine kinase
Myristate
Actinbinding
SH2
F
SH3
kinase
G
Abelson kinase
The front end looks a lot like Src!!
Myristate
Actinbinding
SH2
F
SH3
kinase
G
Oncogenic versions of Abelson
Abl
Actinbinding
SH2
SH3
F
G
F
G
F
G
kinase
v-abl
Gag
Bcr-Abl
Bcr
What’s changed??
Abl
Actinbinding
SH2
SH3
F
G
F
G
F
G
kinase
v-abl
Gag
Bcr-Abl
Bcr
Remember this?
Src is normally
inactive due to
intramolecular
inhibition
The structure of Abl reveals
a novel mode of intramolecular inhibition
Nagar et al.
Cell 112:859 (2003)
Src and Abl
Distinct yet analogous modes of regulation
Harrison Cell 112, 737 (2003)
A multistep mechanism
for activating Src
Harrison Cell 112, 737 (2003)
A proposed mechanism
for activating Abl
Harrison Cell 112, 737 (2003)
But what does Abl
normally do?
Insights from the mouse model
• abl mutant mice are viable
but runted and have a shortened lifespan
They also have problems with:
male fertility
B cell maturation
osteoblasts and bone formation
• Truncation of C-terminus leaving an intact kinase
has same phenotype as the null mutant
Insights from the mouse model
•
Why
so
mild??
abl mutant mice are viable
but runted and have a shortened lifespan
They also have problems with:
male fertility
B cell maturation
osteoblasts and bone formation
• Truncation of C-terminus leaving an intact kinase
has same phenotype as the null mutant
Abelson has a twin brother
Abl
Actinbinding
SH3 SH2 kinase
34% 89%
Arg
94%
F
G
F
G
27%
Are Abl and Arg redundant?
• arg mutant mice have behavioral defects
(Arg is expressed in the brain at high levels)
Are Abl and Arg redundant?
• arg mutant mice have behavioral defects
(Arg is expressed in the brain at high levels)
• abl; arg double mutants have defects in neural tube
Wild-type
abl; arg
Focal adhesion proteins are phosphorylated
by Abl (mediator of integrin signaling)
Abl phosphorylates regulators
of the actin cytoskeleton
Of course it’s even more complicated
Than that!
Bradley and Koleske jcs.biologists.org/cgi/content/ full/122/19/3441/FIG3
Abl can also
directly regulate
Cytoskeletal events
Using its
C-terminal region to
bundle actin filaments
and
Link them
to microtubules
But does this all help us
understand and treat leukemia?
normal person
Leukemic patient
red
blood
cells
white
blood cell
hyperproliferation
of white blood cells
BCR-Abl affects multiple cell functions
Proliferation &
differentiation
Stem cell turnover
S
G2
M
BCR-Abl
G1
G0
Cytoskeleton/
adhesion defects
Apoptosis
Adapted from Jörgensen,
2001. Hem. Onc
.
Abl may play roles in the nucleus
in response to DNA damage
•ATM can phosphorylate Abl
in response to DNA damage
•Abl may stabilize p53
Van Etten, TICB 9 179-186
To understand this, we must start by
learning more about the
clinical progression of CML
Advanced phases
Chronic phase
Median 5–6
years
stabilization
Accelerated
phase
Blast crisis
Median duration
6–9 months
Median survival
3–6 months
Provided by: Gleevec.com
Blast crisis is thought to involve additional
genetic changes that are only beginning
to be characterized
Suggested events:
•Mutations in p53
•MSI2/HOXA9 fusion protein
•AML1/EVI-1 fusion protein
•Ras mutations
•Deletion of the Ikaros transcription factor
Therapy for CML:
how do you evaluate
whether a drug is working?
Hematologic Response
Cytogenetic Response
– Complete:
Normal peripheral blood count
No immature cells
– Major:
Complete: 0% Ph+
Partial 1-35% Ph+
– Minor:
36%–95% Ph+
Modified from Gleevec.com
Therapeutic Options for CML
• Allogeneic stem cell transplantation (SCT)
• Interferon-alpha (IFN-)–based treatments
• Chemotherapy with hydroxyurea, busulfan
• Gleevec™ (imatinib mesylate, = STI571)
From Gleevec.com
Until recently interferon-alpha treatment
Was the gold-standard in CML
Even though its mechanism of action
IS STILL NOT UNDERSTOOD
Data of the Italian Cooperative Study group on
Chronic Myeloid Leukemia. Blood 1998:92 1541–1548
IFN=interferon-alpha, CHT= conventional chemotherapy
Gleevec blocks the ATP binding site of the kinase domain
STI571
Abl’s
Kinase
Domain
In complex
With the
inhibitor
Gleevac
Kuriyan lab website
Gleevec™:
in chronic phase CML
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see t his picture.
Chronic Phase CML
1.0
Major cytogenetic response
0.9
0.8
Complete cytogenetic
response
0.7
Fraction of patients
that responded
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
1
2
3
4
5
6
7
8
9
10
Months Since Start of Treatment
Data: Novartis Pharmaceuticals Corporation
This is an awesome drug!
Most patients survive 10+ years
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see t his picture.
Chronic Phase CML
1.0
Major cytogenetic response
0.9
0.8
Complete cytogenetic
response
0.7
Fraction of patients
that responded
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0
1
2
3
4
5
6
7
8
9
10
Months Since Start of Treatment
Data: Novartis Pharmaceuticals Corporation
Of course there are side effects...
Drug was discontinued for adverse events
in 1% of patients in chronic phase,
2% in accelerated phase,
and 5% in blast crisis
And the cost.....
$40,000-50,000 per year!!
Unfortunately, natural selection is
a powerful process
“We now know of over 30 different mutations
that can cause BCR-ABL to become
resistant to imatinib,” says Dr. Charles Sawyers
of UCLA’s Jonsson Cancer Center. In patients
with newly diagnosed disease, we are seeing
resistance to imatinib in about 4%of patients per year.
The further the disease has progressed before
initiating imatinib treatment,
the greater the chances are that resistance will arise.”
Unfortunately, natural selection is
a powerful process
About 17% of all patients
develop resistance in 5 years
Science 331: 1542-44 March 25 2011
A possible solution: a new generation of kinase inhibitors that
Still inhibit Gleevec-resistant tumors
aka Dasatinib
Inject Luciferase-expressing tumor cells
Science 2004 305:399-401
Dasatinib FDA approved for patients with relapses
NCI Cancer Bulletin October 5, 2006
aka Dasatinib
Inject Luciferase-expressing tumor cells
Dasatinib FDA approved for patients with relapses
NCI Cancer Bulletin October 5, 2006
Leads to 73% progression free survival for 3 years
Dasatinib FDA approved for patients with relapses
NCI Cancer Bulletin October 5, 2006
Phase II trials suggest Dasatinib effective in Blast-Crisis
Patients with Gleevec-resistant tumors
NCI Cancer Bulletin May 2 2007
Phase II trials suggest Dasatinib effective in ALL patients
with Gleevec-resistant tumors
NCI Cancer Bulletin May 29 2007
This is becoming a general approach
Science 331: 1542-44 March 25 2011
How much do you think that costs?
For CML Add another $70,000/year!
Gleevec also has promise in other tumors
e.g., Gastrointestinal Stromal Tumors
90% of malignant GISTs harbor a mutation in c-kit
leading to KIT receptor autophosphorylation and
ligand-independent activation
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
http://www.answers.com/topic/gist-2-jpg-1
Gleevec also has promise in other tumors
e.g., Gastrointestinal Stromal Tumors
90% of malignant GISTs harbor a mutation in c-kit
leading to KIT receptor autophosphorylation and
ligand-independent activation
Does not respond to chemotherapy (<10% response)
Only can be effectively treated if the entire tumor
Can be removed surgically
Without this median survival 1-2 yrs
With Gleevec treatment ~50% of patients respond
Tumors shrink in size
and disease symptoms are greatly reduced
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see t his picture.
Report from the FDA
Approval Summary: Imatinib Mesylate in the Treatment
of Metastatic and/or Unresectable Malignant
Gastrointestinal Stromal Tumors
Dagher et al.
Clinical Cancer Research3034 3034–3038,
October 2002
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
April 17, 2008
Gleevec treatment also reduces risk or recurrence
After surgical removal of GISTs
97% of patients treated with Gleevec had no recurrence after 1 year
Versus 83% of those receiving placebo
GIST
Gleevecxtends median survival
from 15 months to 5 years
But.....
Long term outcome ?
Many patients who initially respond develop
secondary resistance to Gleevec and relapse
Cause: second site mutations in c-kit!
GIST
Long term outcome ?
Many patients who initially respond develop
secondary resistance to Gleevec and relapse
Cause: second site mutations in c-kit!
Approach: Develop new drugs
targeted against c-kit
e.g., AMG706, SU11248
Current Oncology Reports (2005) 7: 293-299
An alternate approach:
broader spectrum inhibitors
that hit multiple targets
Sunitinib: targets Abl/PDGF Receptor, Src,
and VEGF Receptor
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
George Demetri, MD
FDA approved after
Phase III clinical trial reveal
efficacy in GIST patients whose
Tumors are resistant to Gleevec
NCI Cancer Bulletin Oct. 31 2006