CANCER

• TYPES OF TUMOUR?

  BENIGN

  • grow large
  • slower
  • normal nucleus
  • specialised cells
  • adhesion molecules, cells stick together
  • surrounded by capsule
  • less life-threatening (but disrupt functioning of vital organs)
  • localised effects
  • removed by surgery
  • rarely reoccur after treatment

  MALIGNANT

  • grow large
  • rapid
  • larger and darker nucleus
  • unspecialised cells
  • metastasis (no adhesion molecules)
  • no capsule (finger-like projections into tissues)
  • life-threatening as normal tissue is replaced with abnormal
  • systemic effects
  • radiotherapy/ chemotherapy and surgery
  • reoccur after treatment
• WHAT ARE THE TWO GENES THAT PLAY A ROLE IN CANCER?

  oncogenes and tumour suppressor genes
• ONCOGENES?

  • mutations of proto-oncogenes (stimulate cell to divide when growth factors attach to protein receptor on cell-surface membrane, activates genes causing DNA replication)
  • an oncogene is permanently activated because...

  1. receptor protein is permanently activated so cell division is switched on even without a growth factor
  2. oncogene may code for a growth factor so produced in excessive amounts

  • most mutations are acquired with only a few being inherited
• TUMOUR SUPPRESSOR GENES?

  • slow down cell division, repair mistakes in DNA and control apoptosis (programmed cell death)
  • if mutated it is inactivated
  • stops inhibiting cell division
  • e.g. TP53, BRCA1, BRCA2
  • most mutations are acquired with only a few being inherited
• ABNORMAL METHYLATION OF GENES?

  HYPERMETHYLATION OF TUMOUR SUPPRESSOR GENES

  • increased methylation
  • in promoter region
  • inactivates gene
  • inhibits transcription of promoter region
  • gene silenced
  • increased cell division
  • e.g. in BRCA1

  HYPOMETHYLATION OF ONCOGENES

  • activation
  • increased cell division
• OESTROGEN CONCENTRATION AND CANCER?

  • regulates menstrual cycle
  • after menopause, risk of breast cancer increases
  • fat cells of breasts produce more oestrogen
  • develops tumour, further increases oestrogen concentration
  • WBCs drawn to tumour, further increases oestrogen concentration
  • tumour develops further