2. Introduction
CML is a clonal myeloproliferative neoplasm
Dysregulated production and uncontrolled proliferation
of mature and maturing granulocyte with fairly normal
differentiation
Fusion of 2 genes: BCR (or chromosome 22) and ABL1
(on chromosome 9), resulting in BCR-ABL1 fusion gene
Final result: Abnormal chromosome 22 called
Philadelphia (Ph) chromosome
Final product: BCR-ABL1 fusion protein, a dysregulated
tyrosine kinase
3. Uncontrolled production of mature and maturing
granulocytes
Predominantly neutrophils, but also basophils and
eosinophils
Triphasic or biphasic clinical course
Chronic phase, accelerated phase, blast crisis
Introduction
4. Phases of CML (before Imatinib)
Chronic phase
Median duration
5–6 years
Accelerated
phase
Median duration
6–9 months
Blast crisis
Median survival
3–6 months
Advanced phases
5. Epidemiology
Annual incidence: 1 to 2 cases per 100,000
15% – 20% of all adult leukemias
Incidence increases significantly with age
– Median age: ~ 55 years
– Prevalence increasing due to current therapy
– Most patients present in CP, 85%
• Majority of CML-related deaths due to progression to AP/BC
– 50% of CML patients are asymptomatic at diagnosis
Risk factors
– Exposure to ionizing radiation, the only known
6. Molecular Genetics of CML
The Philadelphia chromosome was originally detected by
workers in Philadelphia.
The first genetic abnormality to be associated with a
human cancer.
The result of a balanced translocation between
chromosomes 9 and 22.
Derivative chromosome 22 is significantly smaller
Ph chromosome is present in hematopoietic cells from
patients with CML.
Therefore, the Ph chromosome is acquired and NOT
inherited through the germline.
7. Molecular Genetics of CML
The development of chronic phase CML appears to be a
direct result of the BCR-ABL1 activity, which promotes
its development by allowing:
I. Uncontrolled proliferation of transformed cells
II. Discordant maturation
III. Escape from apoptosis
IV. Altered interaction with the cellular Matrix
The progression of CML from chronic phase to accelerated face or
blast crisis is a complex, multistep process (may be related to GMP).
Also, it appears to involve the constitutive expression of the BCR-
ABL1 tyrosine kinase.
10. bcr-abl Gene and Fusion Protein Tyrosine Kinases
p210Bcr-Abl
p185Bcr-Abl2-11
2-11
Chromosome 9
c-bcr
Chromosome 22
c-abl
Exons
Introns
CML Breakpoints
ALL Breakpoints
1
2-11
11. Diagnosis of CML
Typical findings in the blood and bone marrow
Requires the detection of the Ph chromosomal or its
product, the BCR-ABL1 fusion mRNA and the BCR-ABL1
protein.
Conventional cytogenetic analysis (karyotyping) – The first
method
Florence and in situ hybridization (FISH) analysis
RT-PCR (The BEST)
Southern blot techniques – rarely used
Western Blotting – low sensitivity and labor intensive
12. Accelerated Phase CML
10-19% blasts in the peripheral blood or bone
marrow
Peripheral blood basophils ≥20%
Platelets < 100,000/microL, unrelated to therapy
Platelets > 1,000,000/microL, unresponsive to
therapy
Progressive splenomegaly and increasing WBC,
unresponsive to therapy
Cytogenic evolution
13. Blastic Phase CML
Blasts in the peripheral blood ≥20% or in the bone
marrow ≥30%
Large foci or clusters of blasts on the bone marrow
biopsy
Presence of extramedullary blastic infiltrate (e.g.,
myeloid sarcoma, also known as granulocytic
sarcoma or chloroma)
Blast crisis is generally refractory to treatment, occurs
approximately 3-5 years after the diagnosis of CML and
18 months after the onset of accelerated face
14. Prevalence of the Ph Chromosome
in Hematologic Malignancies
Leukemia % of Ph+ Patients
CML 95
ALL (Adult) 15–30
ALL (Pediatric) 5
AML 2
Faderl S et al. Oncology. 1999;13:169-180.
15. Normal Bcr-Abl Signaling*
• The kinase domain
activates a substrate
protein, eg, PI3
kinase, by
phosphorylation
• This activated
substrate initiates a
signaling cascade
culminating in cell
proliferation and
survival
PP P
ADP P
P
PP P
ATP
SIGNALING
Bcr-Abl
Substrate
Effector
ADP = adenosine diphosphate; ATP = adenosine triphosphate;
P = phosphate.
Savage and Antman. N Engl J Med. 2002;346:683
Scheijen and Griffin. Oncogene. 2002;21:3314.
16. Imatinib Mesylate:
Mechanism of Action*
• Imatinib mesylate
occupies the ATP
binding pocket of
the Abl kinase
domain
• This prevents
substrate
phosphorylation
and signaling
• A lack of signaling
inhibits proliferation
and survival
P
PP P
ATP
SIGNALING
Imatinib
mesylate
Bcr-Abl
Savage and Antman. N Engl J Med. 2002;346:683.
17. Typical Laboratory Parameters
by Phase of CML
Parameter Chronic Accelerated Blast Crisis
WBC count 20 x 109/L — —
Blasts 1%–09% 10-19% 20%
Basophils 20% —
Platelets or normal or
Bone marrow Myeloid hyperplasia
Cytogenetics Ph+
Bcr-Abl + + +
Phase of CML
WBC = white blood cell; Ph+ = Ph chromosome–positive.
18. Molecular Methods for Detecting bcr-abl
at the Ph Chromosome
Fluorescence in situ hybridization (FISH)
Interphase Metaphase
Courtesy of Charles Sawyers, UCLA.
19. 0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5
Years After Transplant
S
u
r
v
i
v
a
l
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
S
u
r
v
i
v
a
l
June 2001, based on transplants 1987 - Feb 2001
Chronic Myelogenous Leukemia
Survival by Disease Stage
First Chronic Phase (n=1903)
Accelerated and 2nd CP (n=744)
Blast Phase (n=159)
P=0.0001
20. Other Possible Mechanisms of
Resistance to Imatinib Mesylate
Mechanisms of resistance
Ph+ cell lines
– Bcr-Abl overexpression
– Gene amplification
– Drug reflux mediated by P-glycoprotein
– Other
In vivo murine model
– Binding in the plasma of alpha 1-acid
glycoprotein to imatinib mesylate
21. Evolution of Resistance to Imatinib Mesylate in CML
Chronic Phase Blast Crisis Relapse
Ph-positive
Ph-negative
Ph+ blasts
Ph+ imatinib-
resistant blasts
Hematopoietic
differentiation
Bonemarrowtoperipheralblood
Courtesy of Charles L. Sawyers, MD.
23. Prevention of BC by more effective treatment in early CP as shown
by the cumulative incidence of blast crisis (German CML Study
Group experience 1983-2011).
7