Heamatology

Question 0

What is the cause of bone marrow aplasia? What happens when the bone marrow is aplastic?

Answer 0

• Toxin induced -Immune damage of the stem cell
  This causes the rate of cell death > proliferation resulting in bone marrow death and low peripheral blood counts ( bone marrow failure)

Question 1

How does the bone marrow (granulocytes) respond to infection?
What happens when the infection is cleared?

Answer 1

Infection causes productin of certain GF’s which stimulate the production of granulocytes. The bone marrow will then have an increased no? of granulocyte precursors. The WCC in the blood increases.
When the stimulus for the production of growth factors is removed the WCC count reverts to normal.

Question 2

What is the product of underlying genetic changes resulting in malignancy? What exactly results in ‘tumour’ formation?

Answer 2

Genetic changes result in either excessive proliferation or decreased cell death by apoptosis.
The cell is no longer able to respond to normal mechanisms of controls resulting in an accumulation of cells, a tumour.

Question 3

What is the difference between acute and chronic leukaemia?

Answer 3

Acute: short clinical course preceding death if untreated.
Chronic: long clinical course

Question 4

What stimulates cell proliferation? In what two form does this product exist?
Explain the process by which this product works.
What is the result of the end product.

Answer 4

Growth factors- soluble molecules or surface bound ( cell- cell contact required.)
Binding of GF( a ligand) to receptor triggers a intercellular signaling cascade resulting in activation of transcription factors which localize the nucleus and initiate the transcription of proteins required for the process of cell division.
This means that the cell will then move from Go to Gi phase of the cell cycle.

Question 5

Explain the two main mechanisms of apoptosis.

Answer 5

1. Receptor mediated pathway: A “death receptor”(eg tumor necrosis factor receptor) on the cell surface binds to its ligand and this triggers an intracellular cascade resulting in activation of a series of enzymes,caspases, which are the executors.
2. Irreparable damage to cellular constituents (eg DNA) is detected and triggers mitochondria to release cyt c. This release is regulated by a family of molecules (Bcl family of proteins) which control the permeability of the mitochondrial mem. Cyt c interacts with members of apoptosis cascade which activates caspases and results in apoptosis.

Question 6

Malignancies arise as a result of failure to regulate which 3 processes.

Answer 6

1. Proto-oncogenes
2. Tumour suppressor genes
3. Apoptosis

** Malignancy usually occurs as a result of accumulation of genetic injuries that affect the function of the different groups of Proto-oncogenes, tumour suppressor genes and regulators of apoptosis.

Question 7

What are Proto-oncogenes? How does malfunction of this gene result in a malignancy?

Answer 7

Genes which code for proteins normally involved in the pathways that stimulate cell division.
Malignancy = over reactivity or “gain of function” of Proto-oncogenes thereby it over promotes cell division and proliferation.

Question 8

What is a tumor surprises or gene and how does its dysfunction result in malignancy.

Answer 8

Genes which normally regulate the cells from over proliferating.
Mutation to this gene = “loss of function” so that the negative regulatory function is lost resulting in proliferation continuing unopposed.

Question 9

Apoptosis: if this pathway is switched off cells accumulate as a result of failure to die rather than excess proliferation. Different gene products are involved in reg of apoptosis as stimulaters or suppressors. Explain how these can be affected?

Answer 9

• Gain of function of the factors which normally inhibit apoptosis
• Loss of function of factors which normally stimulate apoptosis.
  Both result in accumulation of cells.

Question 10

Alteration in oncogenes. What processes result in “gain of function”?

Answer 10

• Amplification of gene: several copies of gene occur.
• Mutation of gene: esp @ sites NB do the reg of function. Product isn’t sensitive to normal control mechanisms.
• Mutation of the regulator genes: Oncogene is unopposed.

-Translocation: Exchange of material btw chromosomes resulting in
A) Production of a fusion gene ( a part of one gene becomes attached to another gene) interferes with structure of product and therefore with its function and susceptibility to regulatory proteins.
B) Transfer of a gene to a site where it is actively transcribed.

Question 11

Explain the relevance of translocation in many B lymphocyte malignancies.

Answer 11

Translocation so occur which move oncogenes to the site of one of the immunoglobulin loci which are actively transcribed and thus the translocation gene falls under the influence of these stimulatory mechanisms.

Question 12

Alterations in oncogenes. Explain by which mechanisms “loss of function” occurs?

Answer 12

• Large deletion a resulting in deletion of the gene
• Small deletions, 1 or 2 bases, which result in production of a totally different protein.
• Mutations result in STOP codons
• Mutations in the promoter sequence so there is decreased expression
• Mutations in the splice regions of the gene- abbé rent splicing at the mRNA level also reduces synthesis of the active protein.

Question 13

How do many current chemotherapy drugs work?

Which tumours would be immune to this?

Answer 13

By targeting the cell cycle and acting by activating apoptosis.

Tumours which express an excess of Genoese inhibiting apoptosis may be resistant to chemotheraputic agents which promote apoptosis.

Question 14

Future chemotherapy is mobbing towards…

Give an example of this and how it works.

Answer 14

Specific drugs which inhibit activated Proto-oncogenes

“Gleevec” - developed to inhibit the Abl oncogene associated with Chronic myeloid leukemia.

Question 15

Haemopoesis starts with _______ which are called _______ stem cells. This type if stem cell capable of __________ .

Answer 15

Progenitor(precursor) cells
Pluripotent stem cells
Differentiate into different haemopoietic cell lines

Question 16

The two main characteristics of a stem cell are…

What does this mean about division(mitosis)?

Answer 16

Self renewal and differentiation.

On division stem cell is able to produce “daughter cells” which have 1) the characteristics if a stem cell again or 2) A more differentiated cell - which loses it’s capacity for self renewal.

Question 17

What causes the differentiation of stem cell daughter cells in a specific lineage? How?

Answer 17

Growth factors in the surrounding environment which interact with receptors on cell surface and stimulate intracellular signaling pathways which determine differentiation.

Question 18

1. Why dies it make logical sense that stem cells are the origin of malignancy?
2. How does this differ from differentiated cells?
3. What is the main difference between the transcription of regulatory proteins on stem cells vs differentiated cells?

Answer 18

1. The are long lived, present for entire life span of individual, therefore able to accumulate multiple genetic alterations.
2. More differentiated cells only have few rounds of cell division before maturing to end stage cells which can’t divide and eventually die. Therefore less likely to live long enough to accumulate the range of genetic alterations necessary for malignant transformation.
   - Stem cells continuously feed malignancy with new cells due to the capacity for self renewal.
3. Stem cells have active transcription of regulatory proteins whereas in differentiated cells many of these genes have been switched off during the process of differentiation.

Question 19

On which 4 factors does the phenotype of a malignancy depend and what are the sub-classification of these?

Answer 19

1. Cell lineage: Myeloid vs Lymphoid
2. Proliferative rate: high in acute leukemias- burkitts or lower in chronic leukemias - chronic lymphocytic/myeloid leukaemia
3. Degree of differentiation of daughter cells in the malignant clone: i) Acute leukemias - accumulation of undifferentiated cells (blasts) ii) Chronic leukaemias and myeloproliferative disorders show differentiation to mature cells.
4. The amount of apoptosis- reduced apoptosis results in accumulation of cells in malignant clone.

Question 20

Explain paradoxical apoptosis and proliferation using an applicable example.

Answer 20

In some turnouts there is increased proliferation together with an increased rate of apoptosis. In myelodysplastic syndromes this results in ineffective haemopoiesis where the bone marrow is hypercellular but the peripheral blood counts are low because cells are dying in the bone marrow and are not released to the blood.

Question 21

Name the aetiological factors involved in the development of malignancy.

Answer 21

1. Environmental
2. Genetic
3. Oncogenes
4. Tumour suppressor genes

Question 22

How do environmental factors cause development of malignancy?

Answer 22

• Radiation: 1)increased incidence with nuclear exposure 2)treatment with radiation resulting in possible 2nd malignancy 3) radio+ chemotherapy increase risk.
• Chemicals: 1) chemotheraputic agents are leukemogenic and can lead to secondary ac,ute leukaemia 2) benzene is myelotoxic resulting in aplastic anemia or acute leukemia 3) smoking increases risk for acute leukemia
• Viruses: 1) HTLV-1 retrovirus transforms T-cells resulting in “Adult T-cell Leukaemia/lymphoma” 2) Epstein Barr virus - burkitts’s lymphoma and Hogkins.
• Virusesy

Question 23

How do genetic factors cause development of malignancy?

Answer 23

Inherited predisposition to leukemia in :

• Down syndrome , trisomy 21, increase risk of acute leukemia.
• Fanconi’s Anemia , Bloom syndrome and Ataxia Telangiectasia predispose to leukemia.
• Identical twins: increase risk if twin has leukaemia
• CLL: increased incidence if 1st degree relative has CLL

Question 24

How do oncogenes form? And how does it result in malignant cells?

Answer 24

Malignant transformation causes a structure of the proto-oncogene to become an oncogene which now encodes for an abnormal protein that can induce and maintain malignant transformation and proliferation of the clone.

Question 25

What are tumour suppressor genes and how do the cause malignancy?

Answer 25

They are involved in regulation of cell proliferation. Deletions or mutations which inactivate these genes are important in the development of malignancies.

Question 26

What are the two main groups of Acute Leukaemia? Why is it important to distinguish between them?

Answer 26

AML and ALL. It is important because they require very different treatment regimens.

Question 27

How are myeloid and lymphoblastic leukaemia’s sub classified further?

Answer 27

1. Morphology of the cells: incl. staining reactions.
2. Expression of cell surface antigens on the surface of the blasts which are characteristic for myeloid or myeloid lineage.
3. Activity of certain enzymes
4. Cytogenic abnormalities: analysis of chromosomes of the blasts

Question 28

Between ALL and AML which is more common in adults and which in children?

Answer 28

• Acute leukaemia: 7% of malignancies in adults in kids it’s the most common malignancy.
• AML most common leukaemia in adults // ALL accounts for 85% of acute leukaemias

Question 29

Acute leukaemia results from the accumulation of _______________ or __________ in the ________ and _______ ________. The diagnosis requires that a minimum of __% _______ be present on analysis if the _____________.

Answer 29

Undifferentiated cells, blasts, bone marrow, peripheral blood.
20% blasts! bone marrow.

Question 30

What are the clinical features of acute leukaemia?

Answer 30

Due to marrow infiltration: anaemia, thrombocytopenia with bleeding and neutropenia with risk of infection.

Due to tissue infiltration: lymphadenopathy(esp. in ALL), gum hyper trophy and skin infiltration (in types of AML), CNS disease ( common in ALL), testicular involvement (May occur in ALL), Splenomegaly

Bone pain: Esp. in children with ALL

Activation of coagulation and fibrinolysis: DIC-like picture with severe bleeding esp. in a subtype of AML, Acute Promyelocytic Leukaemia.

Question 31

What are some of the bad risk factors for the prognosis of ALL?

Answer 31

Age> 35
High white cell count at diagnosis.
CNS disease at presentation
T(9:22) or t(4:11)
\+ 4weeks to achieve remission

Question 32

What is the appropriate treatment of infection?

Answer 32

Empiric treatment should be specific to sensitivity to organisms in the hospital. Must cover both gram positive and gram negative organisms. If no response in + 72 hours add an anti-fungal treatment

Question 33

Define induction therapy.

Answer 33

A course of chemotherapy treatment given to induce remission.

Question 34

Define remission, morphological remission and cytogenetic remission.

Answer 34

Remission: leukaemia is no longer detectable by certain lab methods.

Morphological R : Normalisation of the peripheral blood count and differential count AND <5% blasts in the marrow.

Cytogenetic R : Cytogenetic abnormalities that was present at diagnosis is no longer detectable.

Question 35

Define consolidation therapy.

Answer 35

Chemotherapy given after remission. May be of same or more intensive chemotherapy than induction.

Question 36

Define maintenance therapy.

Answer 36

Less intensive, often oral patient chemotherapy given to maintain remission mostly in ALL

Question 37

Factors contributing to prognosis of AML?

Answer 37

Cytogenetic a of malignancy
Performance status of patient
Age
Primary vs secondary
WCC at diagnosis
Response to induction therapy

Question 38

What are some of the tests to diagnose acute leukaemia?

Answer 38

Full blood could 
Bone marrow aspirated and trephine biopsy
Lumbar puncture to exclude CNS disease
DIC screen
Electrolyte and renal function

Question 39

What is the relevance of a bone marrow aspirate?

Answer 39

Confirms leukaemia if >20% blasts are present
Differentiates AML from ALL
Identifies subtypes with special tests
Cytogenetic and molecular studies

Question 40

What 2 emergencies of acute leukaemia need urgent management and referral?

Answer 40

1. Leukostasis: high (>100) or increasing WBC at risk of plum infiltrate and dysfunction or risk of intracerebral bleeding.
2. Acute Promyelocytic leukemia : at risk of death from DIC with low platelets and fibrinogen. Keep platelets above 20 and fibrinogen >1.5 by transfusing cryoprecipitate

Question 41

How to prevent anaemia?

Answer 41

Give filtered irradiated packed red cells to maintain Hb >8g/dl

Question 42

Prevention of gout and tumour lysis factor.

Answer 42

Hydration to maintain good urine output.
Alkalinise urine with citro-soda.
Allopurinol

Question 43

Prevention of nausea caused by chemotherapy.

Answer 43

Sufficient anti-emetics should be given early to prevent nausea.
Ideally 5HT receptor antagonists should be used if possible but they are expensive.
High dose metoclopromide with dexamethasone may be equally effective.