A couple of years ago, I contributed to a documentary with the intriguing title Catching Cancer. We don’t normally regard cancer as an infection, so it often comes as a surprise to learn that more than 20% of the global cancer burden can be attributed to infections, and that most of these infections are viruses.
To understand this link, we first need a basic understanding of cancer.
What is cancer?
Put most simply, cancer is a collection of cells that have lost their way. Each cell in our body is a machine programmed by the genetic information it contains to perform a specific job. A cancer cell has a corrupted program, with several genes that have acquired mistakes.
Each cell in our body has (approximately) the same genetic information, and passes this on to daughter cells when it divides. Any cell in our body is programmed to use only a subset of that information, which tells the cell whether to be part of your skin, your brain or your blood.
Much of that programming tells the cell what to do when the environment changes. It might be instructed to produce a protein (such as insulin), to divide, to repair itself, or to die. This programing is generally directed by signals from outside the cell.
A cancer cell will have programming mistakes which stop it responding correctly to external directions. The cancer cell will divide inappropriately, lose its specialist function, and become able to move to places it shouldn’t.
Genetic mistakes, once they have arisen, are passed on to the daughter cells, and eventually, the body’s ability to sort the problem fails. When there are enough misbehaving cells present, we recognise this as a cancer.