Oncogenes and tumour suppressor genes

• What do carcinogens cause proto-oncogenes to do?

  Mutate into oncogenes
• What happens to most mutated cells?

  They are destroyed by the immune system
• What are most proto-oncogene mutations caused by?

  Environmental factors
• What do tumour suppressor genes do?

  Slow cell production
• How do tumour suppressor genes work?

  They produce proteins that stop cells dividing, or cause them to self-destruct
• What is the self-destruction of cells also known as?

  Apoptosis
• Which gene mutation do 50% of human cancers involve?

  TP53
• What size and growth rate are benign tumours?

  Potentially large but slow
• What size and growth rate are malignant tumours?

  Potentially large and rapid
• What does the nucleus of a benign tumour look like?

  Relatively normal
• What does the nucleus of malignant tumour cells look like?

  larger and darker due to an abundance of DNA
• What do benign tumours look like?

  Discoloured
• What do malignant tumours look like?

  Discoloured
• Do benign tumours remain specialised?

  Yes
• Do malignant tumours remain specialised?

  No, they may become de-differentiated
• What are the adhesion properties of benign tumours?

  They produce adhesion molecules, which allows them to stick together and stay in the same tissues, forming primary tumours
• What are the adhesion properties of malignant tumours?

  They have no adhesion molecules, so cells spread to other parts of the body via metastasis to form secondary tumours
• Which tumour has a capsule?

  Benign
• What happens because malignant tumours don't have capsules?

  They grow finger-like projections into surrounding tissue
• Do benign tumours pose a threat to life?

  Not often, but they can disrupt the functioning of vital organs
• Do malignant tumours pose a threat to life?

  Yes, more often than not
• What effect do benign tumours have?

  Localised
• What effect do malignant tumours have?

  Systematic
• What treatment is used for benign tumours?

  Surgery
• What treatment is used for malignant tumours?

  surgery, chemotherapy and radiotherapy
• What are the two main factors leading to tumour growth?

  • Abnormal methylation of DNA
  • Increased exposure to oestrogen
• What is an example of hypermethylation?

  BRCA1 gene
• What factors impact oestrogen exposure?

  • Early menstruation
  • Late menopause
  • Taking HRT
• What does an increased exposure to oestrogen increase your chances of?

  Breast cancer
• What are the three theories of oestrogen causing cancer?

  1. Oestrogen stimulates cell division, which increases the chance of cells becoming cancerous
  2. Oestrogen stimulates breast tumour cells to divide quicker
  3. Oestrogen introduces mutations directly into the DNA of breast cells
• How does oestrogen cause uncontrolled cell division? 

  1. Oestrogen binds to a gene that promotes transcription 
  2. Gene is activated 
  3. Cell division is promoted 
  4. Tumour growth develops 
• What effect does oestrogen have on pronto-oncogenes?

  Mutate into oncogenes
• What are the genetic risk factors for cancer?

  • Inherited alleles
  • Hereditary mutations
• What are the environmental risk factors for cancer?

  • Drinking
  • Smoking
  • Diet
• How is diet a risk factor for cancer?

  Increased consumption of saturated fats, not eating enough fruits and vegetables (especially leafy greens and berries)
• What are the methods for preventing cancer?

  • Screenings: physical or genetic
  • Looking for mutated DNA
• What effect does zelboraf have?

  Treats skin cancer by inhibiting the B-RAF enzyme
• What effect does Herceptin have?

  Treats breast cancer by binding to the altered HER2 protein receptor and suppressing cell division and tumour growth