Cancer as a disease: Leukaemia

Question 1

What is the literal meaning of leukaemia

Answer 1

Cancer of the blood

Means white blood

Question 2

Describe the epidemiology of Leukaemia

Answer 2

In the UK approximately 60 people every day are diagnosed with a cancer of the blood
Blood cancers are the most common cancers in men and women aged 15‒24
They are the main cause of cancer death in people aged 1‒34 years

Question 3

How many people in the UK will die of a leukaemia, lymphoma or myeloma

Answer 3

One in 45 of the UK population will die of leukaemia, lymphoma or myeloma

Question 4

Why do we call cancers of the blood leukaemia

Answer 4

Leukaemia means ‘white blood’
The name was given because the first cases of leukaemia recognized had a marked increase in the white cell count which made the blood look whiter
Leukaemia is actually a bone marrow disease and not all patients have abnormal cells in the blood

Question 5

Where exactly does the problem exist in Leukaemia

Answer 5

Leukaemia is actually a bone marrow disease and not all patients have abnormal cells in the blood
Therefore the problem exists in the bone marrow- but you can get overspill into the blood

Question 6

What does Leukaemia result from

Answer 6

Leukaemia results from a series of mutations in a single lymphoid or myeloid stem cell

One mutation is not enough

Question 7

What is the ultimate consequence of these mutations in Leukaemia

Answer 7

These mutations lead the progeny of that cell to show abnormalities in proliferation, differentiation or cell survival leading to steady expansion of the leukaemic clone

Question 8

Outline the schemata for the production of the different blood cells

Answer 8

Pluripotent haematopoietic stem cell – Lymphoid stem cell or myeloid stem cell

Lymphoid stem cell- Pre B Lymphocytes/ Pro T Lymphocytes

Myeloid stem cells- Erythroblasts, myeloblasts, monoblasts,megakaryoblasts

Question 9

In which cells can mutations arise in Leukaemia

Answer 9

Pluripotent haematopoietic stem cell- mutations in this cell type can give rise to mixed phenotype leukaemia- where there are lymphoid and myeloid cells present

Myeloid stem cell- myeloid leukaemias

Lymphoid stem cell- B/T/NK cell leukaemias/lymphomas

Pre B lymphocyte

Pro T lymphocyte

Question 10

When we centrifuge blood and put it into a capillary tube, how may the white cells be visualised

Answer 10

White column
Referred to as the buffy-coat- slightly off-white

This layer will be increased in patients with leukaemia- reflecting the increase in WBC

Question 11

Describe how a leukaemia can arise

Answer 11

Mutation in one of the cells- this mutation does not normally produce any noticeable changes in the cells but it can be detected using molecular and genetic methods.
This will give its progeny a survival advantage, either by:
proliferation (more of them)
differentiation (produce abnormal mature cells)
loss of cell survival (more of them)
susbequent mutations then occur in the progeny- leading to the emergence of a leukemic clone

Question 12

Describe how leukaemia differs from most other cancers

Answer 12

Most cancers exist as a solid tumour
However, it is uncommon for patients with leukaemia to have tumours
More often they have leukaemic cells replacing normal bone marrow cells and circulating freely in the blood stream
So, essentially, leukaemia is diffuse infiltration of the bone marrow- with overspill into the blood.

Question 13

Describe how leukaemia behaves differently to other cancers

Answer 13

Leukaemia is different from other cancer because haemopoietic and lymphoid cells behave differently from other body cells
Normal haemopoietic stem cells can circulate in the blood and both the stem cells and the cells derived from them can enter tissues
Normal lymphoid stem cells recirculate between tissues and blood (through lymphatics)

A epithelial cell isn’t going to move anywhere- it will stay in the epithelium.

Question 14

Differentiate between the terms ‘invasion’ and ‘metastasis’

Answer 14

Invasion- local expansion and penetration into local tissues.
Metastasis- when the tumour moves to a distant site via the blood or lymphatics.

Question 15

Why can’t the terms invasion and metastasis apply to leukaemias and how does this impact their classification into chronic and benign tumours

Answer 15

The concepts of invasion and metastasis cannot be applied to cells that normally travel around the body and enter tissues
We have to have other ways of distinguishing a ‘benign’ condition from a ‘malignant’ condition and haematologists usually use different words for these concepts

Question 16

Describe the classification of benign and malignant leukaemia

Answer 16

Leukaemias that behave in a relatively ‘benign’ manner are called chronic—that means the disease goes on for a long time
Leukaemias that behave in a ‘malignant’ manner are called acute—that means that, if not treated, the disease is very aggressive and the patient dies quite rapidly

Question 17

Summarise the classification of leukaemia

Answer 17

It follows from what has been said that leukaemia can be acute or chronic
Depending on the cell of origin, it can also be lymphoid or myeloid
Lymphoid can be B or T lineage ( or NK lineage)
Myeloid can be any combination of granulocytic, monocytic, erythroid or megakaryocytic- can get multiple lineages affected, or where one lineage predominates.

Question 18

State the different classifications of leukaemia

Answer 18

Acute lymphoblastic leukaemia (ALL)
Acute myeloid leukaemia (AML)
Chronic lymphocytic leukaemia (CLL)
Chronic myeloid leukaemia (CML)

Question 19

Explain the significance of the terms acute lymphoBLASTIC leukaemias and chronic lymphoCYTIC leukaemias

Answer 19

In ALL the cells are immature – they are lymphoblasts

IN CLL the cells are mature lymphocytes

Question 20

Summarise the two key classes of mutations that may occur which explains why people get leukaemias

Answer 20

Leukaemia results from a series of mutations in a single stem cell
Some mutations result from identifiable (or unidentifiable) oncogenic influences
Others are probably random errors—chance events—that occur throughout life and accumulate in individual cells

Question 21

In what percentage of leukaemia patients do we know the cause of their leukaemia

Answer 21

<10%

However, we understand a lot about the mechanisms

Question 22

Describe the important leukaemogenic mutations that have been recognised

Answer 22

Mutation in a known proto-oncogene (cells that give rise to oncogenes but also any normal gene with oncogenic potential).
Creation of a novel gene, e.g. a chimaeric or fusion gene (as a result from chromosomal translocation)
Dysregulation of a gene when translocation brings it under the influence of the promoter or enhancer of another gene ( so the gene is structurally normal- but a promoter or enhancer region of another gene has been translocated onto it which turns it on/off inappropriately).

Question 23

What is the difference between a fusion and a chimaeric gene

Answer 23

Chimeric genes (literally, made of parts from different sources) form through the combination of portions of two or more coding sequences to produce new genes. These mutations are distinct from fusion genes which merge whole gene sequences into a single reading frame and often retain their original functions.

Question 24

What other factors can lead to the development of leukaemias

Answer 24

Loss of function of a tumour-suppressor gene can also contribute to leukaemogenesis—this can result from deletion or mutation of the gene (this can often transform the leukaemia from chronic to acute, as the tumour-suppressor gene was giving the patient some control until it became mutated).

If there is a tendency to increased chromosomal breaks, the likelihood of leukaemia is increased

In addition, if the cell cannot repair DNA normally, an error may persist whereas in a normal person the defect would be repaired

Question 25

State some inherited or constitutional abnormalities that can lead to leukaemogenesis

Answer 25

Inherited or other constitutional abnormalities can contribute to leukaemogenesis, e.g. Down’s syndrome Chromosomal fragility syndromes (fragile X syndrome) Defects in DNA repair (Fanconi anaemia, Werner syndrome, xeroderma pigmentosum). Inherited defects of tumour-suppressor genes

Question 26

State some identifiable causes of leukaemogenic mutations

Answer 26

Irradiation Anti-cancer drugs (can induce mutations which lead to leukaemias) Cigarette smoking Chemicals—benzene

Question 27

How can Leukaemia be described

Answer 27

Leukaemia, like cancer in general, can be seen as an acquired genetic disease, resulting from somatic mutation

Question 28

Differentiate between mutations in germ cells and somatic mutations

Answer 28

Mutation in germ cells may bring favourable, neutral or unfavourable characteristics to the species Somatic mutation may be beneficial*, neutral or harmful * A rare occurrence but can lead to reversion to normal phenotype in some cells in individuals with an inherited abnormality, e.g. an immune deficiency or bone marrow failure syndrome

Question 29

Describe the philosophical interpretation of why people get leukaemias and cancers in general

Answer 29

Since some mutations that contribute to leukaemogenesis appear to be random events rather than caused by an exogenous influence, they may result from the nature of the human genome Leukaemia may thus be, in part, the inevitable result of the ability of mankind to change through evolution

Question 30

What happens in AML

Answer 30

In AML, cells continue to proliferate but they no longer mature so there is A build up of the most immature cells— myeloblasts or ‘blast cells’—in the bone marrow with spread into the blood A failure of production of normal functioning end cells such as neutrophils, monocytes, erythrocytes, platelets - BECUASE THIS LEUKAEMIC CLONE WILL CROWD OUT THE BONE MARROW AND PREVENT THE NORMAL PRODUCTION OF MATURE MYELOID CELLS.

Question 31

Why else may the platelet count be low in acute leukaemias (as well as AML)

Answer 31

One type of acute leukaemia exists where there are complications of DIC- so the platelets are consumes in the vasculature.

Question 32

What mutations take place in AML

Answer 32

In AML, the responsible mutations usually affect transcription factors so that the transcription of multiple genes is affected Often the product of an oncogene prevents the normal function of the protein encoded by its normal homologue (so it's acting in a dominant manner) Cell behaviour is profoundly disturbed (due to the effects on transcription factors).

Question 33

What mutations occur in CML

Answer 33

In CML, the responsible mutations usually affect a gene encoding a protein in the signalling pathway between a cell surface receptor and the nucleus The protein encoded may be either a membrane receptor or a cytoplasmic protein Unlike AML, this doesn't profoundly influence cell behaviour, but it can result in innappropiate activation of the cell.

Question 34

What are the consequences of the mutations of CML

Answer 34

In CML, cell kinetics and function are not as seriously affected as in AML However, the cell becomes independent of external signals, there are alterations in the interaction with stroma and there is reduced apoptosis so that cells survive longer and the leukaemic clone expands progressively

Question 35

How can we distinguish between AML and CML

Answer 35

Whereas in AML there is a failure of production of end cells, in CML there is increased production of end cells AML and CML blood films may both show anaemia- but in CML you will see evidence of maturation and differentiation of myeloid cells and stem cells.

Question 36

What is the key difference between ALL and CLL

Answer 36

Acute lymphoblastic leukaemia has an increase in very immature cells— lymphoblasts—with a failure of these to develop into mature T and B cells In chronic lymphoid leukaemias, the leukaemic cells are mature, although abnormal, T cells or B cells

Question 37

What does the accumulation of immature cells in ALL result in

Answer 37

Accumulation of abnormal cells leading to Leucocytosis, bone pain (if leukaemia is acute), hepatomegaly, splenomegaly lymphadenopathy (if lymphoid), thymic enlargement (if T lymphoid), skin infiltration Bone pain is a common presentation of ALL in children- due to white cells infiltrating bone marrow.

Question 38

How does the skin of a patient with ALL appear

Answer 38

Papular lesion infiltrates

Question 39

What is leukaemia cutis

Answer 39

leukaemia of the skin (skin infiltration)- will cause gross thickening of the skin- can be treated.

Question 40

Describe the metabolic effects of increased leukaemic cells

Answer 40

Metabolic effects of leukaemic cell proliferation—hyperuricaemia and renal failure, weight loss, low grade fever, sweating Hyperuricaemia (due to breakdown of DNA from dying leukaemic cells)- can cause renal failure if uric acid is deposited in the kidneys. Weight loss- metabolism being directed to proliferating white cells. Low grade fever and sweating- due to increased metabolic rate.

Question 41

What are the effects of increased leukaemic cells on other blood cells

Answer 41

Crowding out of normal cells leading to | anaemia, neutropenia, thrombocytopenia

Question 42

Which type of leukaemia increases the risk of a fatal intraventricular haemorrhage

Answer 42

Acute promyelocytic leukaemia (APML) – this is associated with DIC so the platelet count and fibrinogen are low leading to increased risk of fatal haemorrhage Will also present with small bruises Blood shows as white on CT of brain.

Question 43

What are the effects of acute myeloid leukaemia (particularly of the monocytic lineage) on the gums

Answer 43

Monocytes attracted by chemotactic stimuli to the gums and consequently infiltrate the gums: Infiltration of leukaemic cells and monocytes can lead to inflammation of the gums (swelling of the gums) There will be small haemorrhages due to thrombocytopenia This will not happen in patients without any teeth.

Question 44

What is a potential key feature of CLL

Answer 44

Loss of normal immune function as a result of loss of normal T cell and B cell function—a feature of chronic lymphoid leukaemia As the cells are abnormal- it gives a propensity to infection.

Question 45

What is important to remember about the epidemiology of ALL

Answer 45

Acute lymphoblastic leukaemia is largely a disease of children Peak incidence is between 2-5 Also another peak in middle age, but this is a genetically different ALL (due to translocation of chromosomes 9 and 22- which is also the translocation in CML, but this time it occurs in a lymphoid stem cell- so you get a lymphoid leukaemia).

Question 46

What does the data regarding the epidemiology of ALL suggest

Answer 46

Epidemiology suggests that B-lineage ALL may result from delayed exposure to a common pathogen or, conversely, that early exposure to pathogens protects Evidence relates to family size, new towns, socio-economic class, early social interactions, variations between countries A study in Taiwan suggested that enterovirus infection gave protection

Question 47

Explain the factors that may protect against ALL

Answer 47

Essentially, anything that would stimulate your immune system early in life Low socio-economic class- more early exposure to pathogens- kindergartens- more social interactions New towns built on edges of cities= protective- less likelihood of introduction of an unencountered pathogen New town built in countryside= harmful- mixing of people from different cities brining unknown pathogens.

Question 48

Describe some leukogenic factors for ALL in children

Answer 48

Epidemiology also suggests that some leukaemias in infants and young children result from Irradiation in utero In utero exposure to certain chemicals ? Baygon, ? Dipyrone ? Epstein–Barr virus infection Rarely ALL results from exposure to a mutagenic drug- tends to be AML.

Question 49

How can we classify the symptoms of ALL

Answer 49

Those as a result of the accumulation of abnormal cells | Those as a result of crowding out of the bone marrow.

Question 50

List the complications of ALL related to the accumulation of abnormal cells

Answer 50

``` Bone pain Hepatomegaly Splenomegaly Lymphadenopathy Thymic enlargement Testicular enlargement ```

Question 51

How may a lymphadenopathy present in the patient

Answer 51

Swelling of the lymph nodes | Most obvious in the neck.

Question 52

How will thymic enlargement show on a CXR

Answer 52

Will increase the cardiac shadow

Question 53

Describe the complications of ALL resulting from the crowding out of cells in the bone marrow

Answer 53

Fatigue, lethargy, pallor, breathlessness (caused by anaemia) Fever and other features of infection (caused by neutropenia)- particularly bacterial infections. Bruising, petechiae, bleeding (caused by thrombocytopenia)

Question 54

What is meant by petechiae

Answer 54

Small pin-point haemorrhages in the skin

Question 55

If a child comes in with bruises all over the body, as well as investigating abuse, what else should you consider

Answer 55

ALL | Perform a blood count immediately.

Question 56

What are the haematological features of ALL

Answer 56

Leucocytosis with lymphoblasts in the blood Anaemia (normocytic, normochromic) - no Fe or folic acid deficiencies- just crowded out Neutropenia Thrombocytopenia Replacement of normal bone marrow cells by lymphoblasts

Question 57

What investigations should be performed to diagnose ALL

Answer 57

``` Blood count and film Check of liver and renal function and uric acid Bone marrow aspirate Cytogenetic/molecular analysis Chest X-ray ```

Question 58

How will the blood film a patient with ALL show

Answer 58

Lots of lymphoblasts- with increased nuclear:cytoplasmic ratio, delicate chromatin condensations, larger No platelets.

Question 59

Describe how a bone marrow film of a patient with ALL will appear

Answer 59

Lots of lymphobasts- same as blood film

Question 60

What is the purpose of immunophenotyping

Answer 60

To determine the lineage involved in the leukaemia

Question 61

Describe how immunophenotyping works

Answer 61

Pass cells single file through a detector- which picks up fluorescence due to antibody being bound to an antigen. CD10 is common ALL antigen- commonly expressed on B lineage ALL TDT (terminal deoxynucleotidyl transferase)- marker of cell immaturity- so blast cells tend to express this. X-axis -TDT- so further right= more blast cells Y-axis- CD10- so higher up- more B cells Can also look at CD19 for B cell lineage

Question 62

How can you quickly tell from the blood film that it is a myeloid lineage

Answer 62

Granules of mast cells.

Question 63

Describe the importance of cytogenetic and molecular genetic analysis

Answer 63

Cytogenetic/molecular genetic analysis is useful for managing the individual patient because it gives us information about prognosis Cytogenetic/molecular genetic analysis advances knowledge of leukaemia because it has permitted the discovery of leukaemogenic mechanisms

Question 64

Describe how cytogenetic analysis of bone marrow aspirates can dictate the treatment course given

Answer 64

Hyperdiploidy—good prognosis- so need less aggressive treatments t(4;11)—poor prognosis- so need more aggressive treatments

Question 65

Describe the potential consequences of the formation of a fusion gene

Answer 65

Formation of a fusion gene Dysregulation of a proto-oncogene by juxtaposition of it to the promoter of another gene, e.g. a T-cell receptor gene Point mutation in a proto-oncogene

Question 66

Describe reciprocal translocations

Answer 66

Bits of chromosomes are swapped Two detached fragments from two non-homologous chromosomes are switched. Two fusion genes- of which only one tends to be active.

Question 67

Describe the use of FISH in cytogenetics to detect chromosomal translocations

Answer 67

This can be detected by two fluorescent probes, a green probe for ETV6 and a red probe for RUNX1; when a fusion gene is formed the two colours fuse to give a yellow fluorescent signal This technique is called fluorescence in situ hybridization —FISH Used over cytogenetics of bone marrow aspirate when these cells don't go into mitosis.

Question 68

What is a common translocation in T cell lymphomas

Answer 68

t(10;14)(q24;q11)—the TCL3 gene is dysregulated by proximity to the TCRA gene Proto-oncogene brought close to TCR- dysregulation- not a fusion gene!

Question 69

Summarise the treatment for ALL

Answer 69

Supportive Red cells- anaemia Platelets- thrombocytopenia Antibiotics/anti-fungals- neutropenia Systemic chemotherapy- leukaemia is widespread Intrathecal chemotherapy/ systemic drug that can cross BBB- otherwise-patient will enter remission- residual leukaemic cells which will reactivate in CNS.

Question 70

What has been happening to childhood survivial rates with ALL

Answer 70

Increasing gradually. § Overall survival has been gradually been getting better: o Approx. 10-year survival was 10% in 60s, now it is 95%. § Event free survival shows a similar pattern -5% This is due to advances in chemotherapy and better supportive care.

Question 71

What is the difference between overall survival and event free survival

Answer 71

EFS- don't have disease and alive | OS- just alive (so may have disease)

Question 72

What are the disease characteristics of leukaemia due to

Answer 72

Disease characteristics are due to (i) proliferation of leukaemic cells (ii) loss of function of normal cells

Question 73

Why does the treatment for leukaemias need to be systemic

Answer 73

Unlike other cancers, leukaemia is disseminated from very early in the disease process Treatment must therefore be systemic

Question 74

Describe the relationship between prognosis and treatment for leukaemias

Answer 74

It is the molecular genetic events that determine the disease phenotype including the prognosis This in turn determines the optimal treatment for individual patients Increasingly, identification of the precise genetic events underlying the leukaemia indicates the best treatment for an individual patient

Question 75

What other form of treatment may be used in ALL

Answer 75

In poor prognosis cases, bone marrow (or other haemopoietic stem cell) transplantation may be needed. About three-quarters of children with ALL can now be cured.

Question 76

Describe how ALL may cause cranial nerve palsies

Answer 76

Meningeal infiltration

Question 77

What may give rise to CLL

Answer 77

Family predisposition

Question 78

Describe the common results of cytogenetic analysis seen in ALL

Answer 78

``` o Hyperdiploidy = GOOD prognosis o t(4:11) = BAD prognosis o t(12:21)(p12:q22) = ETV6-RUNX1 - fusion gene o t(10:14)(q24:q11) – TCL3 gene is dysregulated by proximity to the TCRA gen ```

Question 79

Describe the different proportions of the different lineages of ALL

Answer 79

· ALL: o 75% - B cell lineage o 25% - T cell lineage