Translocation in Cancer Flashcards
What is a Translocation?
It is a chromosome abnormality caused by rearrangement of parts between non homologous chromosomes.
How can you detect translocation?
Translocations can be detected using mainly FISH, but can also be done using immunohistorchemistry or Sequencing.
What is FISH
It is a molecular cytogenic technique that uses flourescent probes that attach to specific sequences for imaging
What are the 5 steps in FISH
- Specimen preparation - to determine the accessibility of the target and perservation of the morphology
- Probe selection and labeling
- Denaturation of the probe and DNA
- In Situ Hybridzation
- Probe detection and microscopy
4 methods of viewing fluorescence
- Dual colour, break apart - 2 probes flank a know break point
- Dual color single fusion - 2 probes flank one side of a break point
- Extra signal technique - 1 probe spans the breakpoint and 1 probe flanks it
- Dual color dual fusion - 2 probes span the break point
What is ROS1
Proto-oncogene, a receptor tyosine kinase which has a similar structure to the ALK protein
Crizotinib
Form of cancer treatment, used for advanced lung cancer.
Inhibits tyosine kinase
Work by blocking the ALK enzyme.
Two types of pathways in cancer
- Proto onco genes
2. Tumor suppressor genes
Proto onco genes
Involved in cell proliferation pathway, Encourage cell growth and division.
Mutations cause uncontrolled cell growth.
Tumor suppressor genes
Involved in inhibition of cell proliferation by preventing cell growth and division.
Mutations cause uncontrolled cell growth.
Gain of Function
In oncogenes, Amplification - increase in expression Activation - specific point mutations Translocation - increase expression due to movement near promoter 1 allele needs to be affected.
Loss of function
Tumor suppressor gene Deletion - decrease in expression Inactivation - nonsense mutation Gene silencing - DNA methylation 2 alleles need to be affected
Mutations in Proto oncogenes,
Hint 4
- Mutation (deletion or addition) in the coding sequence, leading to a hyperactive protein in normal quantities
- Mutation in regulatory element, leading to a normal protein in high quantities.
- Amplification, leading to normal protein being overproduced
- Chromosomal rearrangements, of either regulatory element, leading to a normal protein being overproduced. Or a rearrangement in the coding seq, leading to a normal production of a hyperactive protein.
What is karyotyping
Process of pairing and ordering all the chromosomes in an organisms. Used to look at structural features by staining.
Karyotyping staining
To visualise the normal chromosome complement of mitotic cells in metaphase. Stained with Giemsa to produce dark G-bands (AT rich gene poor) light- R-bands (CG rich gene rich)
