Lecture 16/17 - Myeloid malignancies

Question 1

Myeloid cells: what are they?

Answer 1

• Granulocytes - eosinophils, neutrophils, basophils
• Monocytes - macrophages etc
• Erythroid and megakaryocytic lineages -

Question 2

AML: what is it, what is it caused by, how is it detected, and what occurs when you suffer from AML?

Answer 2

Acute myeloid leukaemia

Myeloblasts

• Blast cell counts greater than 20% (either in bone marrow or blood - blast cells should not be released from marrow, if they are then they’re prematurely released - bad) - this applies to almost all (PML-RARA is an exception which can rely on translocation instead)
• Directly looking at blood for dysplasia (the presence of abnormal cells)
• Genetic/immunophenotypic markers and morphology

Myeloid accumulation in bone marrow or blood, infiltrate organs etc

Question 3

AML incidence: who are most affected, how many are diagnosed per year, and what percentage of cases occur in those under 25?

Answer 3

Most common at 65yr+

~2000 diagnosed with AML every year

25% of cases in those <25

Question 4

AML genetic mutations: how many are there, what are some of the most common examples, and what is a disease that can transform into AML?

Answer 4

Countless

• Translocations between chromosomes 8 and 21
• Translocations between chromosomes 15 and 17

Prior myelodysplastic/myeloproliferative syndrome/disease (MPD) causes excessive amounts of myeloid cells which overwhelm the bone marrow and prevent functioning cell production - may transform into AML

Question 5

FAB scheme: What is it and what does it do?

Answer 5

French-American and British scheme - classifies AML within 8 sub-categories using different cytochemical stains, immunophenotypes, and molecular genetics

M0 - Undifferentiated blasts
M1 - Lightly granulated blasts
M2 - Granulated blasts often with auer rods
M3 - Promyelocytic leukaemia
M4 - Myelomonocytic leukaemia
M5 - Monocytic leukaemia
M6 - Erythroleukaemia
M7 - Megakarycotyic leukaemia

Question 6

Auer rods: what are they?

Answer 6

Cytoplasmic inclusions found only in the leukaemic cells of some cases of AML

Red and needlelike crystals that contain peroxidase

Question 7

FAB class M3 acute promyelocytic leukaemia (APML): what occurs

Answer 7

Chromosomal translocation - t15-17 blocking differentiation of the promyelocyte into a myelocyte causing promyelocyte accumulation

Promyekotic leukaemia gene and retinoic acid receptor a gene (PML-RARa) are fused and blocks promyleocyte differentiation, found in 98% of these cases

All-transretinoic acid (ATRA) - degrades the fusion product and now induces differentiation of the leukaemic cells

Question 8

M2 AML: granulated blasts with auer rods

Answer 8

t8-21

AML1 gene on 21 and ETO gene on 8

Typically, AML1 encodes the alpha chain of the heterodimeric transcriptional apparatus ‘core binding factor’ which is critical for hematopoietic development

This translocation brings together RUNX1 (a transcription factor) and RUNX1T1 (a co-repressor)

RUNX1 should normally bind with CBF and promote hemopoietic differentiation, maturation, and apoptosis when required, but when bound with RUNX1T1, other co-repressors (including histone deacetylase) bind and myeloid differentiation is prevented

Question 9

Clinical features of AML: what is the general process?

Answer 9

• Dominated by bone marrow failure - myoblast infiltration
• Anaemia, thrombocytopenia, infections
• Skin infiltration and CNS disease - mass infiltration of organs

Question 10

AML: Diagnosis

Answer 10

Diagnosis based on:
* Full blood count
* Blood film looking for blasts
* Bone marrow smear - if they have 20% blasts
* Immunophenotyping - can use clusters of differentiation with monoclonal antibodies to detect which lineage/maturity is affected (CD33 is a common one(?))
* Cytogenetics and molecular genetics - chromosomal antibodies

Question 11

AML treatment

Answer 11

Supportive and specific:
* Often have to treat fever asw
* Treatment of bone marrow

Chemotherapy:
* Induction (remission-reduction)
* Consolidation (post-induction)

Treatment aims to achieve a complete remission (<5% blasts in bone marrow) and consolidation then aims to eliminate any residual cells

Question 12

AML treatment drugs

Answer 12

Cytotoxic and nonspecific

Induction chemotherapy using cytarabine and an anthracycline (daunorubicin)

Consolidation treatment is based on prognostic features - those with favourable prognostic factors will get shorter, easier treatment

• Myelotoxic - limited selectivity: they destroy all marrow cells
• Bone marrow failure (as cells get destroyed)

Question 13

Immunotherapy

Answer 13

Massive area of science

Involves using the immune system to reject and destroy tumours

Question 14

Anti CD33 therapies

Answer 14

Specifically destroy granulocyte and macrophage precursors

Mylotarg: gemtuzumab ozogamicin - a monoclonal immunoconjugate targeted against CD33 to treat AML, originally controlled trials failed to demonstrate safety and efficacy using it with other chemotherapeutic agents but now can be used with daunorubicin and cytarabine

Question 15

Stem cell transplantation

Answer 15

Autologous - patients own marrow used and collected while the patient is in remission

Allogenic - marrow from a normal donor with same tissue type (often using close relatives)

Question 16

AML prognosis

Answer 16

Very vraiable
Dependent on age and prognostic factors like cytogenestics

Question 17

Survival rate as age increases

Answer 17

Children - ~50%
Young adults - ~50%
Elderly (>65) - <5%

Question 18

CML

Answer 18

Chronic myeloid leukaemia

Proliferation of mature granulocytes (n,e,b) and their precursors is the main finding

Most clinically researched haematological malignancy - first to be associated with a chromosomal abnormality (Philadelphia chromosome - t(9;22), BCR-ABL1+)

• Block between myelocyte and poly
• Accounts for ~15% of leukaemia
• May occur at any age
• Overall incidence of 5-10 cases/million population
• First to have significant reported success with a molecular targeted therapy - imatinib

Question 19

Philadelphia chromosome: what occurs with it and

Answer 19

Reciprocal translocation between the long arm of chromosome 9 and 22, resulting in fusion between proto-oncogene ABL and the BCR gene on chromosome 22 resulting in a chimeric BCR-ABL protein which causes tyrosine kinase production and stimulation of abnormal blood cell production

Question 20

ABL1: what does it stand for?

Answer 20

Abelson murine leukaemia viral oncogene homolog 1

Question 21

BCR: what does it stand for?

Answer 21

breakpoint cluster region protein

Question 22

Clinical features of CML: what are they and what is the largest form of diagnosis for it?

Answer 22

• Weight loss
• Night sweats
• Splenomegaly (spleen enlargement) frequently occurs
• Anaemia/bleeding/bruising common

In up to 50% of cases, diagnosis is made incidentally from a routine blood count

Question 23

Lab findings of CML

Answer 23

• Leukocytosis - a common occurrence
• Increased basophils (common)
• Bone marrow is usually hypercellular with a raised myeloid/erythroid ratio.
• The Philadelphia chromosome is detected by cytogenetics - BCR-ABL fusion is detectable by FISH (or PCR)

Question 24

The three phases of CML: what are they, how long do they last, how many blasts are present, what symptoms are present, and what are the relevant features?

Answer 24

Chronic phase:
* 5-6 years
* 10-15%
* Asymptomatic
* Expansion of myeloid compartment

Accelerated phase:
* 6-9 months
* 15-<30%
* Increased tiredness, weight loss, splenomegaly
* New cytogenetic abnormalities

Blast crisis:
* 3-6 months
* >30%
* Increased blood cells in bone marrow and blood, extramedullary disease
* Increased genomic instability

Question 25

Treatment: How treatable are each of the phases and what is the actual treatment?

Answer 25

Chronic phase (CML-CP) - responds well to chemotherapy usually

Blast phase (CML-BP) - fatal, acute leukaemia

Tyrosine kinase inhibitors (TKI) - 4 licensed for use: imatinib and second-generation TKIs bosutinib (not NICE-approved), dasatinib, and nilotinib

Question 26

‘Tinib’ meaning

Answer 26

nib - inhibitors

Tinib - tyrosine kinase inhibitors

Question 27

NICE

Answer 27

National institute for health and care excellence

Question 28

Imatinib: what is it, what does it do, how does it do this, and what issues are there with it?

Answer 28

BCR-ABL tyrosine kinase inhibitor Imatinib (Glivec)

It controls the blood count, clears the marrow of malignant cells, increases the chronic phase, and reduces the risk of acute transformation

Mode of action:
* Block the binding of ATP to BCR-ABL
* Inhibits the activity of the kinase and
* Inhibits the proliferation of BCR-ABL cells.

But…the drug is specific - molecular resistance to Imatinib emerging and second-generation tyrosine kinase inhibitors and beyond (?????)

Question 29

IRIS study: what is it and what did it do?

Answer 29

The International Randomized Study of Interferon and STI571 (IRIS) trial - compared the efficacy and safety of imatinib (IM) with that of interferon-alpha plus low-dose cytarabine in 1106 patients with newly diagnosed chronic-phase CML

Question 30

Dasatinib

Answer 30

• Broad multikinase inhibitor
• Effective in many cases where BCR-ABL1 has acquired mutations rendering it resistant to Imatinib

Question 31

Nilotinib

Answer 31

• A similar mechanism of action to Imatinib
• Higher affinity for BCR-ABL1 kinase