Tumour suppressor gene

A tumour suppressor gene encodes for a tumour suppressor protein. This protein has a role in the normal regulation of cellular proliferation or differentiation. When its role is perturbed tumours arise and cell growth becomes unconstrained.

Hereditary diseases that predispose to neoplasia have been excellent systems for the identification of tumour suppressors. In these diseases, an affected individual has the inherited mutation at birth and thus the primary mutation responsible for tumorigenesis is more easily identified.

Various features of tumour suppressors have been identified:

• a single tumour suppressor gene can predispose to tumours in various tissues
• tumour suppressor proteins may function at various levels within a cell:
  • pRB, the gene product of the RB1 gene in retinoblastoma, acts as a transcriptional regulator
  • neurofibromin, the gene product of the NF1 gene in neurofibromatosis, plays a role in cytoplasmic transduction
• some products of tumour suppressor genes only have roles in the development of tumours e.g. pRB, whereas others play a part in the development of the phenotype e.g. neurofibromin

Examples of tumour suppressor genes include:

• RB1 - retinoblastoma susceptibility gene
• WT1 - Wilm's tumour gene
• NF1 - neurofibromatosis type 1 gene
• NF2 - neurofibromatosis type 2 gene
• DCC - involved in colorectal cancer
• BRCA1, BRCA2 - involved in breast cancer