8.2.11 Tumour Development

Key Genes Involved in Tumour Development

1. Proto-oncogenes:

• Normal Role: Stimulate cell division.
• Mutation Effect: Becomes an oncogene, which permanently activates cell division, leading to uncontrolled growth.

2. Tumour Suppressor Genes:

• Normal Role: Inhibit cell division and repair DNA.
• Mutation Effect: The gene becomes inactive, so cell division becomes uncontrolled, and damaged DNA is not repaired.

Factors Contributing to Tumour Development

1. Mutations:

• Changes in DNA sequence can lead to the activation of oncogenes or inactivation of tumour suppressor genes.
• Mutations may be caused by exposure to carcinogens such as UV radiation, chemicals, or viruses.

2. Abnormal Methylation:

• Hyper-methylation: Tumour suppressor genes are silenced, preventing them from controlling cell division.
• Hypo-methylation: Proto-oncogenes become overactive, promoting excessive cell division.

3. Hormones:

• Increased oestrogen levels, particularly in breast tissue, can activate genes that promote cell division, increasing the risk of tumour development.

Characteristics of Tumour Development

• Loss of Cell Cycle Control:
  • Mutations disrupt normal cell cycle checkpoints, allowing damaged or abnormal cells to divide.
• Uncontrolled Growth:
  • Cells continue dividing despite signals to stop, forming a tumour.
• Invasion of Tissues:
  • Malignant tumours invade surrounding tissues and may metastasise (spread to other parts of the body).
• Resistance to Apoptosis:
  • Cells fail to undergo programmed cell death, leading to their survival and accumulation.

Prevention and Treatment

• Prevention:
  • Avoid exposure to known carcinogens (e.g., tobacco smoke, UV radiation).
  • Maintain a healthy lifestyle, including a balanced diet and regular exercise.
  • Regular screenings to detect tumours early.
• Treatment:
  • Surgery: Removal of the tumour.
  • Chemotherapy: Targets rapidly dividing cells.
  • Radiotherapy: Uses radiation to kill cancerous cells.
  • Targeted Therapies: Inhibit specific molecules involved in tumour growth.