Cancer

Cancer is a disease in which cells grow uncontrollably.

Complex multicellular organisms such as humans consist of trillions of cells that perform a wide variety of defined functions. This exquisite control of cellular function is regulated by multiple genes in the human genome in ways that are only partially understood.

Each individual cell contains a complete genome. Each new cell comprises a copy of the genome from the cell from which it originates. Although cells have multiple quality control and correction mechanisms, errors in DNA duplication can occur.  Such genetic errors, also known as genetic mutations, can also be induced by external causes (for instance, cigarette smoke contains chemicals that damage DNA).  

Mutations can affect the genes that contribute to control of cellular function and multiplication. Cells with such genetic mutations can therefore lose this control and start to grow in an uncontrolled fashion. Since each "daughter” cell will also inherit the cancer-causing mutations, a tumour of cancerous cells can thus start to grow. 

Mutations can also occur in genes that contribute to the quality control of genome duplication. In cells with such mutations genomes are replicated less faithfully. This therefore increases the chances of new mutations arising in the genes responsible for control of cellular function and the risk of cancer developing.  

In cancers novel genetic mutations continue to happen and, as a consequence, evolutionary processes occur that result in cells that grow and duplicate ever faster.

Cancers thus comprise different combinations of mutations and often consist of genetically different cells. Each patient’s tumour is therefore unique and this makes cancer such a very difficult disease to treat.