CML Module Flashcards
Chronic Myeloproliferative Disorders: Definition
Malignant proliferation of myeloid cells (NOT blasts, but maturing cells) in blood and bone marrow
The 4 myeloproliferative disorders
Chronic Myeloid Leukemia (CML)
Polycythemia Vera (PV)
Essential Thrombocythemia (ET)
Myelofibrosis (MF)
What is proliferating in CML?
Neutrophils
What is proliferating in PV?
Red cells
What is proliferating in ET?
platelets
What is proliferating in MF?
Everything
Features of myeloproliferative disorders (general)
Adults Long clinical course Increased WBC with left shift Hypercellular marrow Big spleen Mutated Tyrosine kinases
What can myeloproliferative disorders develop into?
Acute leukemia
Chronic Myeloid Leukemia
Neutrophilic leukocytosis
Basophilia
Philadelphia Chromosome
Three phases
Lab Findings of CML
Increased WBC Neutrophilia with Left Shift Basophilia Decreased Hgb Increased platelets Decreased LAP
LAP
enzyme in neutrophils.
In benign process - high.
Malignant - low.
Philadelphia Chromosome
Chunk of 9 breaks off - adds to 22.
22 is the Philadelphia chromosome
Makes active TYK
Symptoms of CML
Slow onset
Fever, fatigue, night sweats
abdominal fullness (splenomegaly)
Signs of CML
Big spleen and big liver
3 phases of CML
Chronic, accelerated, blast crisis
Chronic CML
Stable counts, controlled
Accelerated CML
50% from chronic.
Unstable. Blast crisis in 6-12 months
Blast Crisis
50% for chronic.
Acute leukemia of either lineage.
High mortality
Remission of CML
Best detected by PCR. No BCR-ABL1
About Polycythemia Vera
High RBCs (makes blood sludgy)
Different from secondary polycythemia (altitude)
Thrombosis and hemorrhage
JAK2 mutation
Polycythemia mean…
increased red cell mass
Primary polycythemia
intrinsic myeloid cell problem
secondary polycythemia
increased EPO
Clinical signs of PV
headache, pruritis, dizziness
Thrombosis, infarctions
Symptoms of PV
big spleen and liver. Flushing.
JAK2 Pathway
Unique pathway that does not involve secondary messengers. Brings growth factors to nucleus and stimulates division.
JAK STAT in PV
Mutated JAK2
Inhibitory portion does not work - continually signaling
Treatment of PV
phlebotomy
Maybe myelosuppressive drugs
Prognosis
Median survival 9-14 years
Death from thrombosis or hemorrhage
Leukemic transformation in some patients
About Essential Thrombocythemia
Very high platelet count
Young women
Diagnosis of exclusion
Thrombosis and hemorrhage
Diagnostic criteria for ET (platelet)
Platelet count > 600,000
Diagnostic criteria for ET (Hgb)
> 13 or RBC mass normal
Diagnostic criteria for ET
Platelets count >600,000
RBC mass normal or Hgb >13
No Philadelphia chromosome or marrow fibrosis
Signs and Symptoms of ET
Bleeding, thrombosis (even though lots of platelets - they aren’t working)
Purpura, bruising, pallor, tachycardia, big spleen
Treatment of ET
platelet pheresis
Maybe myelosuppressive drugs
Aspirin
Prognosis of ET
5-8 years
Death from thrombosis or hemorrhage
Leukemic transformation
Chronic Myelofibrosis course
panmyelosis — then marrow fibrosis
Extramedullary hematopoiesis
Hallmark of Myelofibrosis (Smear)
Teardrop red cells
Signs and Symptoms of MF
LUQ fullness, weakness, fatigue, palpitations
Splenomegaly, pallor, tachy
Treatment of MF
Supportive
Maybe myelosuppressive drugs
Prognosis of MF
3-5 years
Death from marrow failure
Leukemic transformation possible
Why is the SH3 domain important?
It is a common motif to establish multi enzyme complexes
BCR-ABL1 mimics what?
Growth factor activation
Mechanism of Imatinib
ATP binding site competitive inhibitor
SE of Imatinib
muscle cramps asthenia (wasting syndrome) edema skin fragility diarrhea tendon and ligament abnormalities
Why does Imatinib have broad SE?
TYK have many families. May work on many different ‘branches’
What is so special about Imatinib?
It is a small molecule drug that binds at the ATP binding site for kinase activity, rather than selectively inhibiting the BCR-ABL1 protein.
Has less collateral damage than one would think
What enzyme metabolizes Imatinib
CYP3A4 (grapefruit juice = bad)
Resistance to Imatinib
Altered metabolism CYP3A4
Altered membrane transport
Loss of p53 (which confers resistance to apoptosis)
Over expression of BCR-ABL1
Point mutations, especially in binding domain
Biggest mutation in CML
T313I
What happens in T315I mutation
Loss of binding parter, big thumb sticks out of binding pocket.
Imatinib can no longer keep from phosphorylating and cell signaling will continue as a result.
How common is T315I?
30% of cancers resistant to Imatinib have this mutation.
Nilotinib
Induces deeper and faster remissions
lower levels of BCR-ABL transcripts
Side effects of Nilotinib?
Same as Imatinib
How does Nilotinib work?
Has a hydrophobic binding pocket with fluorine group
Does Nilotinib work with T315I resistance?
No
Dasatinib
Works against BCL-ABL1 and Src
Active against point mutations, except T315I
SE of Dasatinib
fluid retention and pulmonary HTN
Inhibits some threonine and serine kinases (DIRTY)
Bosutinib
Active against BCR-ABL1 and Src
Works on most point mutations, except T315I
Ponitinib
Designed based on T315I
Active against this mutation
SE of Ponitinib
Causes clots and arterial fibrosis that can be fatal
Treatment of CML is an example of…
successful molecular medicine
Initiating event of CML?
Translocation at (9;22)
What happens with t(9:22)
Genomic translocation creates new gene encoding for an active tyrosine kinase
What differentiation pathway does CML affect?
Neutrophil
Neutrophils arise from…
hematopoietic stem cells –> then Multipotential progenitor and Common myeloid progenitor
3 stages of Neutrophil development
Stem cell - undergoes self renewal and proliferation
Progenitor - just proliferation
Committed - neither - one fate
Self renewal and proliferation are tightly regulated by..
extracellular signaling from marrow. Immune system.
ensures that appropriate number of neutrophils are produced.
BCR-ABL1 is a….
constitutively active tyrosine kinase - activates proliferation and blocks apoptosis in the absence of extracellular signals.
Where does the BCR-ABL1 mutation arise?
Hematopoietic stem cell
Passed down to all progeny
Expression of BCR-ABL1 fusion protein disrupts….
normal neutrophil differentiation
BCR-ABL and selective advantage?
Progenitor cells proliferate more and survive longer
Acquire more mutations to become oncogenic
Do constitutively active BCR-ABL1 cells self renew?
NO.. still mature
How does CML develop into the accelerated/blast phase?
GMP acquires ability to self renew. Blocks differentiation. Results in huge expansion on immature cells
What does b-catenin do?
transcription factor activated by WNT extracellular ligand
Self renewal of stem cells
Mutation in b-catenin leads to…
Blast crisis
What happens in the translocation event?
Genomic DNA is physically rearranged between 9 and 22
Which one is the philadelphia chromosome (9 or 22)
22 (22q-)
Mechanism for translocation?
non-homologous end joining
p210 or p190
Normal role of BCR
inhibition of inflammatory response
Normal role of ABL1
Kinase used for DNA repair, cytoskeletal organization
what normally regulates ABL1 activity
myristate, a long chain FA
ABL is mainly located _____, BCR-ABL is _______
nuclear, cytoplasmic
the ______ domain of BCR promotes dimerization
coil-coil
_____ attachment is lost from ABL1 in mutation
myristate
Tyrosine 177
BCR phosphorylation creates new binding site on Y177 (in mutated protein)
Signaling in normal ABL
myristate blocks, then extracellular signaling, opens conformation, dimerization occurs allowing transphosporylation
Phos TK are the platforms for signaling
Signaling in BCR-ABL1
No myristate so open (no signaling needed), coil coil of BCR promotes dimerization.
Why is Y177 only subject to phosphorylation in mutation?
BCR isn’t a tyrosine kinase normally
Why does the inactivation of BCR-ABL result in apoptosis?
Mutant cells depend on the pathway
Why must imatinib be taken for life?
Doesn’t work against stem cells. If stop, quiescent stem cells will restart the disease
