Cancer

• Uncontrolled cell division– Mass of cells:

‘tumour’

• 1 in 4 deaths in developed countries– Most common in

men: lung cancer– Women: breast

cancer

Eg Hairy Cell Leukaemia

• Cancer in bone marrow– Produces unusual

white blood cells– Susceptible to

infection

Mutation

• Mutation in DNA– Common, but most mutations cause death of the cell

(eg by immune response), so no problem

• If the mutated gene prevents control of mitosis (causes cancer) it is called an oncogene– Mutated gene is passed onto all descendents (billions

of cells)

• Many individual mutations required to form an oncogene

Mutagens

• Mutagens cause mutations– (carcinogens cause cancer)

1. Ionising Radiation

2. Chemicals

3. Virus Infection

4. Heredity

Ionising Radiation

• X rays, gamma rays, alpha & beta radiation• Form ions in cells

which break DNA strands

• UV: lack of ozone causes skin cancer

Chemicals

• Tar from tobacco smoke, dyes (eg anilines)

Virus Infection

• Eg Burkitt’s Lymphoma in Africa

• Form of leukaemia

• Papilloma viruses (eg cervical cancer: sexual transmission)• Viruses can carry oncogenes

Heredity

• Normally a genetic link to predisposition– Do not inherit the disease itself, but

susceptibility to the factors that cause the disease

• But some cancers can be inherited directly– Eg retinoblastoma

• Causes blindness and death if not treated

• Mutation on chromosome 13

Development of Tumour

• Primary Growth– Small bunch of cells– May be benign or malignant– Both use resources (food supply etc) for cell growth &

division

• Benign– Do not spread– May compress surrounding tissue– Eg warts, ovarian cyst, brain tumour

• Malignant (cancerous)– Spread & invade other tissue

Metastasis

• Malignant Tumours may block intestine, lungs, blood vessels

• Cells break off and travel in blood to other areas (metastasis)– Very serious form, hard to

locate & remove ‘secondary growths’