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PCR Application: Can Breast Cancer be Cured?

PCR Application: Can Breast Cancer be Cured?. Normal, Healthy Cells. Cells can change or differentiate to become specialised according to the tissue that they make up

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PCR Application: Can Breast Cancer be Cured?

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  1. PCR Application: Can Breast Cancer be Cured?

  2. Normal, Healthy Cells • Cells can change or differentiate to become specialised according to the tissue that they make up • A healthy cell performs the correct functions according to its type and specialised state. This feature of cells is controlled by our DNA.

  3. Normal, Healthy Cells Properties of a healthy cell

  4. Very common to get DNA mutations How does a healthy cell deal with this? • Cell suicide – keeps the number of cells balanced and removes cells with badly damaged DNA Repair DNA e.g. BRCA protein

  5. Normal, Healthy Cells

  6. DNA Mutations Mutations are a change in the base nucleotide sequence of our DNA e.g. Deletion A T G C G A T A T C G T T G e.g. Insertion A T G C G A  A T G GC G A Changes in the DNA sequence change the amino acid sequence of the protein.

  7. DNA Mutations • If a gene becomes mutated, cells can start to lose control and become cancerous • This can lead to the formation of a tumour

  8. Cancer cells arise from genetic mutations

  9. Cancerous Cells

  10. External Factors • Physical Carcinogens • E.g. UV Radiation from sunlight • Biological Carcinogens • E.g. viruses such as HPV can create an opportunistic environment for cancer • Chemical Carcinogens • E.g. Tobacco, alcohol

  11. External Factors Inherited Gene Mutations

  12. What is a Genotype? • Genotype • Genetic makeup of a cell – the set of alleles that a person has. A gene may exist in two forms, so the different possibilities are: BB or Bb or bb • Phenotype • The observable (way it looks) physical or biochemical appearance of an organism. Determined by genotype and environmental influences. Genetic makeup of a cell – the set of alleles that a person has. A gene may exist in two forms: one form is dominant (B) and one form is recessive (b) BB or Bb or bb Phenotype The observable (way it looks) physical or biochemical appearance of an organism. Determined by genotype and environmental influences.

  13. Example TYPICAL FORM MUTANT FORM (WILD TYPE)

  14. Genotype Terminology • Heterozygous – when the cells contains 2 different alleles at a gene locus e.g. Bb • Homozygous – when identical alleles of the gene are present on both homologous chromosomes e.g. BB or bb

  15. Inherited Mutations • The BRCA2 genecodes for a protein that repairs DNA • An individual with a Bb genotype for BRCA2 is more susceptible to accumulating DNA damage and is consequently at a higher risk of breast cancer • Tumours arise from cells where Bb has spontaneously mutated to become bb with time

  16. Inherited Mutations When DNA mutations are inherited they occur in every cell of the body

  17. What Does High Risk of Breast Cancer Mean? • 12% of women without any inherited mutations will develop breast cancer in their lives • 45% of women with a harmful BRCA2 mutation will develop breast cancer by 70 years of age

  18. Managing Risk Angelina Jolie has an inherited BRCA2 mutation and elected to have her breasts removed as a preventative measure

  19. How did she know? • A DNA sample would have been taken (from her blood or • saliva) and this sample would have been sent to a testing • laboratory • Then the BRCA2 gene locus would have been amplified • by PCR and her genotype analysed by gel electrophoresis

  20. Managing Risk • Other options; • Enhanced screening – frequent mammograms • Chemoprevention – possibly tamoxifenor ralaxifenemay help to reduce risk, but this has not yet been proven

  21. How can we kill cancer cells with BRCA2 Mutations? Chemotherapy? Radiotherapy?

  22. The Problem with mutated BRCA • The mutation in the BRCA (bb) gene in tumour cells is not enough to induce cell suicide • AND BRCA mutated cells do not respond very well to chemotherapy or radiotherapy • Can we use the BRCA mutation to our advantage for treatment?

  23. Overcoming this Problem • Treating cancer by inhibiting the other DNA repair genes: • Synthetic Lethality Normal Cell with PARP inhibitor drug BRCA2 mutant cell with PARP inhibitor drug BRCA2 Mutant Cell Normal Cell DNA Damage BRCA PARP BRCA PARP BRCA PARP BRCA PARP Survives Survives Survives Death

  24. Synthetic Lethality NOBRCA2 + NO other=CELL DEATH mechanisms of cancer cells of DNA repair + Chemotherapy or Radiotherapy Synthetic lethal treatments are currently being researched in Cardiff University and elsewhere as a potential new therapy for breast cancer

  25. Your Task Your PCR samples are from 4 individuals with or without BRCA2 mutations Your tasks are to: GENOTYPE each sample PHENOTYPE each sample

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