Session 4 - Molecular Biology of Leukaemia and Lymphoma

Question 1

Outline the process of normal B cell development

Answer 1

• Antibody producing cells
• Formed in the bone marrow
• Transported to peripheral tissue for further maturation in the lymph nodes => process occurs as first antibodies are beginning to be expressed
• Undergoes proliferation in the germinal centres of the lymph nodes

Question 2

What process happens to B cell in the lymph nodes

Answer 2

• Somatic hyper-mutation

Question 3

What is somatic hyper-mutation, what are its benefits and what can it lead to?

Answer 3

o Cysteine in the region of the genome coding for the variable chain of antibodies is deaminated via specific enzymes
o Cytosine deamination leads to double stranded break in the DNA and rearrangement
o The repair process causes mutation
o This give diversity to antibodies
o Occurs in the cells that are most highly proliferating cells in the human body
o DNA breaks and proliferation => ideal way to produce lymphomas

Question 4

What does epstein barr virus do?

Answer 4

• Attaches and activates B-lymphocytes CD21

- Enters cell and undergoes lytic replication

Question 5

What is EBV associated with? Three conditions

Answer 5

o Heterophile positive infectious mononucleolus
o Burkett’s Lymphoma
o Nasopharyngeal Carcinoma

Question 6

Give two types of burkitt’s lymphoma

Answer 6

o	Sporadic (west) 
o	epidemic (viral Epstein-Barr)

Question 7

What is the histology of burkitt’s lymphoma cells?

Answer 7

o Sheets of cells => tangible body macrophages
o Starry sky appearance
o Blue with large nuclei

Question 8

What is the reciprocal chromosomal translocation in Burkitt’s lymphoma?

Answer 8

t(8,14) - Moves c-myc to an area of 14 regulated by antibody heavy chain locus.
This cuases uncontrolled constitutive expression of the gene.

Question 9

What does c-myc do in a cell?

Answer 9

• Master regulator of cell metabolism and proliferation
• If overexpressed leads to many metabolic changes in the transformed cells
• Function in cell cycle and proliferation
• Allows cell transformation in translocation

Question 10

How can chromosomal 8:14 translocation be diagnosed?

Answer 10

o Fluorescent in situ hybridisation

 Look for large translocation

Question 11

What proportion of non-hodgkin’s lymphoma does follicular lymphoma make up?

Answer 11

20-30%

Question 12

Give some signs and symptoms of follicular lymphoma

Answer 12

o	enlargement of the lymph nodes in the neck, underarm, stomach, or groin,
o	fatigue, 
o	shortness of breath, 
o	night sweats, 
o	weight loss

Question 13

What is the gene change in follicular lymphoma?

Answer 13

• Reciprocal translocation between 14 and 18, t(14,18)

o Affects BCL2

Question 14

What is the function of BCL2 in the cell?

Answer 14

o Involved in cell survival
o Prevents apoptosis via intrinsic pathway
 Prevent oligomerasation of BAX and BAK
• When oligomerised they creates a hole in the mitochondria allowing initiation of apoptosis
 Stabilises mitochondria to resist apoptotic stimuli
o Cell immortalisation

Question 15

What is the mechanism of action of BCL2 upregfulation in carcinogenesis

Answer 15

o Reduced apoptosis => allows further mutations and progression to cancerous state

Question 16

What is the chromosomal translocation in diffuse large B-cell lymphoma?

Answer 16

•	Chromosomal translocation t(3,14)
•	BCL6  is affected 
o	If found at very high levels
	Protective outcome 
	Better response to conventional chemotherapy

Question 17

What does increased bcl-6 do?

Answer 17

o Maintains the germinal cell proliferations
o If downregulated B cells exit the germinal cells but when it is upregulated they remain in the germinal centres increasing level of proliferation and leading to further mutations
o The disease is very heterogenous

Question 18

Give some gene markers for

Answer 18

Diffuse large B-cell lymphoma?
o	CD10
o	BCL6 
o	MUM1
o	Potential way to distinguish between different co-types
o	Not entirely successful

Question 19

How can genetic changes be tested in diffuse large B-cell lymphoma

Answer 19

o Tested by DNA hybridisation in diffused large B-cel lymphoma

Question 20

Give some others changes in diffuse large B-cell lymphoma

Answer 20

o Lost
o BLIMP1 is lost
 Stimulates differentiation of B cells once they leave the germinal centre
 Downregulates BCL6 in order to allow exiting of the cells out of germinal centres
 Lack of it will induce greater proliferation

Question 21

What does BCL6t enhancement and BLIMP loss lead to?

Answer 21

• BCL6 enhancement and BLIMP loss leads to increased time period of proliferation of B cells leading to induction of mutations and cancer development

Question 22

What happens genetically in mantle cell lymphoma?

Answer 22

	Translocation t(11,14)
	Heavy chain and cyclin D1 
	Cyclin D1
o	Comes on in G1 and drives cells into synthesis phase 
o	Maintains proliferation 
	Many varieties

Question 23

What can be used to detect diffeent types of mantle cell lymphoma

Answer 23

 Flow cytometry can be used to detect different types of Mantle cell lymphoma
o Detects surface markers
o Mechanical means => single cell hit by laser
1. Monoclonal antibodies bind to the certain receptors
2. Antibodies are fluorescently labelled
3. Type of antibody can be detected as it is hit by the laser emitting light signal

Question 24

What viruses are found lymphoma?

Answer 24

HHV8

HTLV-1

Question 25

What does HHV8 cause lymphoma wise?

Answer 25

o Primary effusion lymphoma
o Only in immunosuppressed patients (transplants and HIV)
o 3 different diseases
o Virus protein can insert into the cell and activate GPCR stimulating proliferation

Question 26

What does HTLV-1 cause lymphoma wise/

Answer 26

• Adult T-cell leukaemia lymphoma

Question 27

What does adult T-cell leukaemia cause?

Answer 27

o Affects CD4 and CD25
 Positive cells
o Clinical forms

Question 28

What occurs in acute adult t-cell lymphoma

Answer 28

Acute leukaemia

• Leukaemic picture, organomegaly, high lactate dehydrogenase (LDH) and often hypercalcaemia

Question 29

What occurs in chronic adult t-cell leukaemia?

Answer 29

• Lymphocytosis >4×109/l with ATLL cells, skin, lung, liver or node
• involvement
• Calcium levels normal, LDH normal or less than twice the upper normal limit

Question 30

What is chemoprevention?

Answer 30

Use of natural or synthetic compounds to reverse, suppress, prevent or delay carcinogenic progression to invasive cancer

Question 31

Give some lifestyle suggestions for protecting yourself from Cancer

Answer 31

1) Be as lean as possible without being underweight
2) 30 minutes physically active 30 mins/day
3) Avoid sugary drinks – Limit consumption of energy dense foods
4) Eat more varieties of vegetables, fruits, whole-grains and pulses
5) Limit consumption of red meats and avoid processed meats

Question 32

Give two types of Chemopreventive Agents in Cancer

Answer 32

Blocking agents

Supressing agents

Question 33

What are blocking agents?

Answer 33

Compounds which inhibit carcinogenesis by preventing carcinogens from being generated or from reaching, or reacting with, critical target sites in tissues.

Question 34

What are supressing agents?

Answer 34

Compounds which act after carcinogenic exposure by suppressing the expression of neoplasia

Question 35

What is the difficulty when you’re assessing the efficacy of Chemoprevention?

Answer 35

There has to be a palpable end to the trial – requires the use of surrogate end point biomarkers

Question 36

What two issues does the use of surrogate end point biomarkers bring up

Answer 36

requires a detailed understanding of the Cancer process in any given tissue and a detailed understanding of the mechanism of action of the chemopreventive agent.

Question 37

What are some host factors which differ from patient to patient?

Answer 37

Drug metabolising enzymes – Susceptibility to carcinogenic effects of cigarette smoke – altered response to chemopreventive agents which require metabolism
Repair enzymes – Ability to repair DNA
Receptors, kinases, transcription factors – Cell signalling

Question 38

Why is a diet targeted therapy good?

Answer 38

Need agents where there is pre-existing evidence of safety. Often consumed in diet regularly, considered relatively safe. Multi-targeted – can interfere with many pathways involved in carcinogenesis.

Question 39

Give two models of carcinogenesis?

Answer 39

Chemical models

Mutant or genetically engineered models

Question 40

What are chemical models of carcinogenesis?

Answer 40

Tumours in rodents induced by chemical carcinogens. Tumour development rapid; localisation and nature of tumour dependent on dose, strain of rodent etc

Question 41

What are some mutant or genetically engineered models?

Answer 41

Rodents which carry mutations in genes implicated in the initiation or progression of cancer or where the gene can be knocked out or mutated.

Question 42

Give three examples of agents which were attempted chemoprevenativie agents

Answer 42

Tamoxifen
Aspirin
B-carotene

Question 43

Why was tamoxifen used, and what’s wrong with it?

Answer 43

Anitoestrogen in breast tissue, benefits extended beyond 5-years of treatment. Endometrial cancer and venothrombolic events increased, however – Devil and the deep blue sea!

Question 44

Why was aspirin used?

Answer 44

Low dose aspirin reduces inlammation and thus cancer promotion

Question 45

What happened with beta carotene?

Answer 45

Believed it would be a useful chemopreventive agent for lung cancer, actually proved the opposite. May have been wrong dose, perhaps converted to co-carcinogen in presence of tobacco smoke. Other consitutents of the fruits and vegetables ingested to eat B-carotene may have been the cause.