14. Leukaemia Flashcards
(41 cards)
In what age group is leukaemia the most common cancer, and the main cause of cancer death?
- Most common cancer - 15-24 years
* Main cause of cancer death - 1-34 years
What is lymphoma and myeloma?
- Lymphoma - tumour of lymphoid cells
* Myeloma - neoplasma of plasma cells
What is leukaemia?
Cancer of the white blood cells in the bone marrow
Do all leukaemia patients have circulating tumour cells?
No
What brings about leukaemia?
- Series of mutations in a single lymphoid or myeloid stem cells
- Normally at least 2 mutations
- Lead to abnormalities in proliferation, differentiation and cell survival
What cell can give rise to both myeloid and lymphoid cells?
Pluripotent haematopoietic stem cell
What do lymphoid and myeloid stem cells give rise to?
- Lymphoid - B and T lymphocytes
* Myeloid - granulocytic, monocytic, erythroid or megakaryocytic
Outline the first and second mutation in a blood stem cell?
• Initial mutation - growth advantage
- uncontrolled expansion, crowding out the normal polyclonal cells
• Second mutation - even more aggressive behaviour
- can be an interval of years between the 2 mutations
Why can’t leukaemia be defined as benign and malignant and what is used instead?
- Normally, a concept for solid tumours is invasion (local spread) and metastasis
- Neither can be regarded as abnormal behaviour for haematopoeitic and lymphoid cells, as they normally recirculate between tissues and blood
- Described as chronic or acute instead
What is chronic and acute leukaemia?
- Chronic - leukaemias that behave in a relatively benign manner
- Acute - leukaemias that behave in a malignant manner
What are the 4 main types of leukaemia (refer to stem cells and types)?
- Chronic lymphocytic leukaemia (CLL)
- Chronic myeloid leukaemia (CML)
- Acute lymphoblastic leukaemia (ALL)
- Acute myeloid leukaemia (AML)
How can you remember if a lymphoid cell cancer is acute or chronic?
- lymphoCYTIC = chronic
* lymphoBLASTIC = acute
What gene mutations can cause leukaemia?
- Proto-oncogene mutation
- Creation of a novel gene e.g. chimeric
- Translocation may bring a normal gene under the influence of the promoter
- Loss of function of TSG
- Tendency to chromosomal breaks
What inherited or other constitutional abnormalities can contribute to leukaemogenesis?
- Down’s syndrome - increased propensity to ALL and AML
- Chromosomal fragility syndromes
- Defects in DNA repair
- Inherited defects of TSGs
What are environmental causes of leukaemogenic mutations?
- Irradiation
- Anti-cancer drugs (ironic)
- Cigarette smoking
- Chemicals e.g. benzene
Leukaemia can be seen as an acquired genetic disease, resulting from a somatic mutation - mutations can be beneficial or neutral, what does this mean?
- Beneficial - rare, but can lead to reversion to a normal phenotype in some cells in individuals with an inherited abnormality
- Neutral - mutation doesn’t give the cell any particular growth or survival advantage (no leukaemia)
Are mutations that contribute to leukaemogenesis more likely to be random or caused by an exogenous influence?
Random (nature of the human genome - side effect of the ability to evolve)
What generally happens in AML?
- Cells continue to proliferate
- No longer mature - build up of immature cells (myeloblasts) in the BM with spread to the blood
- Failure to produce various end blood cells - can result in anaemia
What are the 2 reasons for a low platelet count in leukaemia?
- Failure of production of normal functioning end cells
* Disseminated intravascular coagulation
What protein is affected by a mutation in AML and CML?
- AML - transcription factors
- CML - signalling protein gene (encodes protein in signalling pathway between a cell surface receptor and nucleus - membrane receptor or cytoplasmic protein)
Are cell kinetics and function more seriously affected in AML or CML?
AML
Does the cell become independent of external signals in AML or CML?
CML
How does the production of end cells differ in AML and CML?
- AML - failure of production of end cells
* CML - increased production of end cells
What is the difference between ALL and CLL?
- ALL - increase in immature cells (lymphoblasts) - failure to develop into mature T and B cells
- CLL - cells are mature, but abnormal