SickKids Cancer Sequencing Program
Our bodies are made up of billions of cells. Our cells contain our genetic material, or ‘DNA’. DNA, or the ‘genome’, includes our genes which serve as the instruction manual for how our bodies grow and develop. Genes may tell our body to have blue eyes or curly hair. Genes can also influence what health conditions we develop either as children or as adults. Genes influence our traits by coding for proteins. To make proteins, our DNA sends a message to the machinery in our cells. This message is in the form of ‘RNA’.
We all have differences, or variants, in our DNA. These variants can be harmful (called ‘pathogenic’) or harmless (called ‘benign’). The term ‘germline variant’ refers to a genetic change that we are born with, and is present in every cell of our body. The term ‘somatic variant’ refers to a genetic change that we acquire over our lifetime. A somatic change may only be present in a group of cells, or in one part of the body.
Cancer is caused by harmful variants (also called ‘mutations’) in important genes. These mutations cause the gene to stop working properly, and lead to uncontrolled cell growth. In most cases, these mutations happen by chance. In other cases, cancers develop in individuals who have an underlying ‘predisposition’ for tumour development. This means that there may be a genetic variant that they were born with (in their germline), or that they inherited, that makes them more susceptible to getting cancer. A cancer’s mutations can serve as a ‘fingerprint’ to follow its progress, and can provide important information about how to specifically treat it. Researchers have learned that different tumours have different mutations, even if the cancer started in the same organ.