What is a tumour suppressor gene?
The tumour suppressor genes in a healthy cell work together with another class of genes, called proto-oncogenes, to control cell reproduction. Tumour suppressor genes code for proteins that restrain cell growth, and proto-oncogenes specify proteins that stimulate cell growth. Mutations in either type of gene can disrupt the delicate balance between inhibition and activation of the molecular processes that regulate a cell’s life cycle, leading to the uncontrolled cell growth characteristic of cancer. A mutation in one gene alone does not cause a malignant tumour to develop; a number of genetic insults occurring in a few different genes over time are necessary for a cell to undergo transformation to a malignant state. For example, a proto-oncogene becomes a cancer-causing oncogene (q.v.) when mutated in a manner that increases the cell’s propensity to divide excessively. In order for a cell to give rise to cancer, other mutations, such as damage to a tumour suppressor gene, must arise.
