RLO: Cell Division

Cell Division and Disease

All cells have a limited lifespan, varying from hours to decades, depending on the cell type and the factors that damage the cell. In normal tissues, the rate of cell division and the extent of cell destruction are similar. This balance of cell production and death is controlled by genes that regulate mitotic division. Some hormones and growth factors activate genes and trigger cell division. Other genes have been shown to inhibit cell division, and these genes are known as repressor genes.

If these control mechanisms become abnormal the rate of cell division exceeds the rate of cell death. The tissue begins to swell and a tumour is created. In a benign tumour cell growth is eventually restricted and such tumours rarely threaten life. However, some tumours, known as malignant tumours, no longer respond to the normal control mechanisms. Over half of all malignant tumours are associated with abnormal forms of a repressor gene.

Cells from these malignant tumours, called primary tumours, can spread to the surrounding tissues to establish secondary tumours. The malignant cells that can spread to other tissues of the body are called cancer cells.