2.3.7 Uncontrolled Cell Division & Cancer

Key Features of Uncontrolled Cell Division:

1. Regulation of the Cell Cycle:

• Normal cell division is controlled by checkpoints in the cell cycle, which ensure:
• DNA is accurately replicated.
• Damaged cells are repaired or destroyed (apoptosis).
• Uncontrolled cell division occurs when these checkpoints fail due to mutations in specific genes.

2. Genes Involved in Cell Cycle Regulation:

• Proto-oncogenes:
• Promote cell division under normal conditions.
• Mutation converts them into oncogenes, which cause uncontrolled cell division.
• Tumour suppressor genes:
• Inhibit cell division and trigger cell death in damaged cells.
• Mutation in these genes allows cells to divide uncontrollably.

Formation of Tumours:

1. Benign Tumours:

• Grow slowly and remain confined to their original location.
• Do not invade other tissues or spread to other parts of the body.
• Often encapsulated and easier to remove surgically.

2. Malignant Tumours:

• Grow rapidly and invade surrounding tissues.
• Cells can break off and spread via the blood or lymphatic system (metastasis).
• Malignant tumours are cancerous and more difficult to treat.

Causes of Cancer:

1. Genetic Mutations:

• Changes in DNA that affect proto-oncogenes or tumour suppressor genes.

2. Carcinogens:

• Substances that increase the risk of cancer by causing DNA damage.
• Examples include tobacco smoke, UV radiation, and asbestos.

3. Lifestyle Factors:

• Poor diet, lack of exercise, and excessive alcohol consumption increase cancer risk.

4. Infections:

• Certain viruses (e.g., HPV) can cause cancer.

Treating Cancer:

1. Chemotherapy:

• Uses drugs to disrupt the cell cycle by:
• Preventing DNA replication.
• Interfering with spindle formation during mitosis.
• Affects rapidly dividing cells, including healthy cells, which causes side effects like hair loss.

2. Radiotherapy:

• Uses radiation to damage DNA in cancer cells, triggering cell death.

3. Surgery:

• Removes tumours, often combined with chemotherapy or radiotherapy to kill remaining cancer cells.