15. Haematological Malignancies

Question 1

haematological malignancies

Answer 1

Clonal diseases -cells affected share a unique mutation theyre clones of that cell

Cell: undergone genetic changes (somatic mutation) leading to malignant transformation. Mutation is not inherited; it is a mutation that has been acquired by the cell

Excessive proliferation
Resistance to apoptosis

Question 2

Clonal diseases: derived from a single cell that has undergone genetic alteration

Answer 2

overtime the % of bone marrow cell population would be less normal haemopoietic tissue and more malignant cells after mutation, especially after clonal expansion when they become the majority of cells within the bone marrow

Question 3

pathogenesisi of haematological malignancy

Answer 3

Cause:

• environment
• toxin
• virus infection
• drug
• genetic disposition

To pathogenesis, altered gene expression

• oncogene
• tumour suppression gene

To:
translocation
mutation
amplification 
deletion 

showing the phenotype

• decreased apoptosis
• increased proliferation
• decreased differentiation (don’t become a mature cell)

(clone of malignant cells)

Question 4

what causes malignancy

Answer 4

number of factors

usually a combination of genetic predisposition and environmental factors including: 
Infection
Ionizing radiation
Chemicals
Drugs

Question 5

genetic predisposition causing malignancy

Answer 5

Genetic predisposition:

Downs syndrome - increased incidence of leukaemia [acute].

Question 6

infection causing malignancy

Answer 6

Infection:
Viruses:
human T-lymphotropic virus type 1 (HTLV-1) - adult T-cell leukaemia/lymphoma (ATLL). HTLV Increased risk of developing lymphoma or leukemia – involves the cell that was involved in the initial infection. T cells infected by virus, leukemia associated is a t cell leukemia or lymphoma

Epstein-Barr virus – leaves person at risk of Burkitt’s lymphoma
Bacteria:
Helicobacter pylori infection - gastric lymphomas. GI tract

Question 7

infection causing malignancy - ALL (acute lymphoblastic anemia)

Answer 7

Proportion of childhood ALL:
initiated by genetic mutations that occur during development in utero

? Environmental exposure during pregnancy
2nd transforming event within tumour cell after birth ie needs to develop second mutation. Two hit hypothesis
? Abnormal response of immune system to infection, unclear mechanism
Children for e.g. in nursery daycare
decreased incidence of ALL in comparison to those living in more isolated communities with decreased exposure to common infections in early years

Twin studies – both may be born with same chromosomal abnormality happened in utero
Second transforming event: different for both twins, one develops ALL at ~5, other remains well until 14 (Wiemals JL et al. Blood (1999):1057-62

Question 8

ionising radiation causing malignancy

Answer 8

causes mutations

increases risk of malignancy - Hiroshima and Nagasaki following atomic bomb blasts

Question 9

chemicals causing malignncy

Answer 9

Benzene (chronic) in cig smoke - chromosomal abnormalities in leukaemia

Question 10

drugs cuasing malignancy

Answer 10

Drugs:
Alkalyting agents, e.g.chlorambucil - myeloid leukaemia.
Chlorambucil is a treatment for cancer, myeloid leukemia. But cann affect other cells and cuse malignancies also

Question 11

mechanism of malignancy

Answer 11

Dysregulation of genes involved in:

• proliferation, differentiation and cell survival
• Leads to altered signalling pathways

These abnormal genes are known as:

• oncogene (normal partners: “proto-oncogenes“)
• Tumour supressor genes

Question 12

oncogenes

Answer 12

Derived from proto-oncogenes

Gain of function mutation
-amplification, point mutations or chromosomal translocations

Uncontrolled proliferation
Blockage of differentiation or
Prevention of apoptosis

overproduction of immature cells that wont die

Question 13

the dual nature of oncogenes

Answer 13

normal protooncogene has essential cellular functions

A transforming oncogene becomes a cellular oncogene to altered cellular functions to spontaneous neoplasm

Question 14

tumour suppressor genes (TSG)

Answer 14

Commonly involved in cell-cycle

Inactivation of a tumour-suppressor gene:

• by deletion or mutation
• loss of function mutations
• promotes malignant transformation

Encode for proteins that negatively regulate proliferation

p53 most significant TSG in human cancers (~50% of malignant disease)

here, they lose a function

Question 15

Proliferation of normal cells depends on

Answer 15

balance between proto-oncogenes and tumour suppressor genes
if protooncogene and TSG balanced, leads to regulated proliferation and apoptosis
however if eg radiation virus mutation, and no TSG, and only oncogenes we get malignant cells with excess proliferation and failure of apoptosis

Question 16

Genetic abnormalities associated with Haematological Malignancies

Answer 16

Point mutations

Gene and chromosomal deletions

Chromosomal duplication (e.g. trisomy 12 in CLL) or gene amplification (not common)

Question 17

Frequent genetic abnormalities in leukaemia and lymphoma

Answer 17

myeloid AML M3 (subclass cell type) disease, genetic abnormality at t (15;17) (translocation), involving the oncogenes RARalpha and PML
myeloid CML disease genetic abnormalilty at t (9;22) and oncogene involved is ABL, BCR
lymphoid disease follicular lymphoma genetic abnormality is at t (14;18) and oncogene involved is BCL-2 to IgH

Question 18

The role of / detection of genetic markers

Answer 18

3 main roles in haematological malignancies:

1. Initial diagnosis
2. Sub-classification using genetic markers
3. Monitoring minimal residual disease to make sure no malignant cells within their circulation

Question 19

1. diagnosis of haematological malignancies

Answer 19

blood tests, symptoms are usually not specifc to a particular disease, we need to know where translocation is and whether it is of B or T cell

Genetic abnormalities [e.g. t(15; 17) or t(9; 22)]:

• specific for a particular disease
• determine the diagnosis

Clonal immunoglobulin or T cell receptor (TCR) rearrangements:

• determine clonality
• establishing if malignancy is of either B or T cell lineage.

Question 20

2. sub classification of haematological malignancy

Answer 20

presence of a particular translocation

t(14;18) in diffuse-large B cell lymphoma
prognostic information for this group of patients

Question 21

3. monitoring minimal residual disease:

Answer 21

Minimal residual disease (MRD):
Low level of disease detectable using available methods

Diagnosis:
possible that patient will have approximately 1013-1014 malignant cells.

After treatment (trying to reach MRD):
patient is described as being in remission when less than 5% of blasts detected in the marrow.
Can equate to 108-1010 blasts still remaining
usually below the detection limit of conventional techniques.

need sensitive techniques to detect malignant cell in large population of other cells to show treatment is effective

Question 22

3. Monitoring minimal residual disease (cont’d)

Answer 22

Molecular techniques, PCR capable of detecting 1 malignant cell in up to 106 normal cells

Translocations: disease specific and are therefore very useful for MRD monitoring.

Presence of MRD: provides a high risk of relapse allowing the potential of additional therapy prior to relapse.

MRD not detected: risk of relapse is low allowing the potential reduction in treatment

Question 23

minimal residuall disease

Answer 23

Treatment – remission. Theyre not cured, require further treatment to maintain remission and ensure all malignant cells are being affected and continuing treatment all the way down to look at cure
But can relapse – disease specific and what equipment is available
decreasing curve, remission decreases no of malignant cells to MRD, continues to cure or relapses

Question 24

Assessment of malignant cellsLab techniques

Answer 24

Includes: 
Karyotype analysis
Fluorescent in situ hybridization analysis
Southern blot analysis
Polymerase chain reaction

Question 25

Assessment of malignant cells

karyotype analysis

Answer 25

-Karyotype analysis
Morphological analysis of chromosomes from tumour cells under the microscope
Each chromosome pair shows an individual colour pattern. look for changes

Question 26

Assessment of malignant cells - fluorescent in situ hybridisation

Answer 26

-Fluorescent in situ hybridisation
fluorescent-labelled probes bind to specific parts of genome
detect extra copies of genetic material
presence of chromosomal translocations

Question 27

Assessment of malignant cells southern blot analysis

Answer 27

-Time consuming, relatively insensitive but still used
Extract DNA from leukaemic cells,
restriction enzyme digestion,
gel electrophoresis and
transfer by “blotting” to a suitable membrane
-If translocation has occurred, novel band of different electrophoretic mobility is seen

Question 28

Assessment of malignant cells - polymerase chain reaction

Answer 28

amplify a DNA segment, then sequenced
detect chromosomal translocations
determine the presence of clonal cells in B and T cell malignancies

Question 29

WHO Classification of Haematological Malignancy

Answer 29

Various systems used for classification, for e.g.-

• World Health Organization (WHO) classification of haematopoietic and lymphoid neoplasms began in 1995.
• Based on the REAL (Revised European-American classification of lymphoid neoplasms).
• WHO classification: morphology and genetic features.
• The leukaemia classification uses the French-American-British (FAB) classification but also includes molecular genetics.

Question 30

initial classification of haematological malignancies

Answer 30

Haematological malignancies were primarily classified according to lineage 
Myeloid 
Lymphoid 
Histiocytic/dendritic 
Mast Cell 

Categories then defined by use of:
morphology 
immunophenotype 
genetic features 
Clinical syndromes

Question 31

Classification of haematological malignancy

Answer 31

Lymphoid/Myeloid: acute and chronic

eg lymphoid
Acute Lymphoblastic Leukaemia ALL and subtypes
Chronic lymphocytic leukaemia

eg myeloid
Acute myeloid leukaemia (AML) and subtypes
Chronic myeloid leukaemia (CML)