8.2.8 Epigenetics & Disease

Cancer and Tumours

Cancer occurs when there is uncontrolled cell division, resulting in the formation of a tumour.

• Types of Tumours:
  1. Benign Tumours:
  • Grow slowly and are usually non-invasive.
  • Can cause mechanical damage by pressing against tissues or blood vessels.
  • Do not spread to other parts of the body.
  2. Malignant Tumours:
  • Grow rapidly and are invasive, damaging neighbouring tissues.
  • Can spread to other parts of the body via metastasis (through the bloodstream or lymphatic system).
  • More difficult to treat than benign tumours.

Genes Involved in Cancer Development

1. Proto-oncogenes:

• Stimulate normal cell division by producing proteins that help cells progress through the cell cycle.
• When mutated, they become oncogenes, causing uncontrolled cell division.

2. Oncogenes:

• Formed from mutated proto-oncogenes.
• They permanently:
• Activate cell surface receptors.
• Code for growth factors that overstimulate cell division.

3. Tumour Suppressor Genes:

• Normally regulate cell division by slowing it or causing apoptosis (programmed cell death) when damage is detected.
• If these genes are mutated or silenced, the cell cycle becomes unregulated, leading to tumour formation.

Role of Epigenetics in Cancer

1. Abnormal Methylation:

• Hyper-methylation (increased methylation) of tumour suppressor genes, such as BRCA1, can silence these genes, leading to cancer.
• Hypo-methylation (decreased methylation) of oncogenes can activate them, causing uncontrolled cell division.

2. Oestrogen and Breast Cancer:

• Increased oestrogen levels in post-menopausal women (due to accumulation in adipose tissue) can contribute to breast cancer.
• Oestrogen binds to transcription factors, activating genes that promote cell division and leading to tumour formation.