We know cancer is caused ultimately via a link between the environment and genes. There are genes inside cells that tell cells to grow and the same genes tell cells to stop growing. When you deregulate these genes, you unleash cancer. Now, what disrupts these genes? Mutations.

The gene that enables birds to learn songs can become cancer-causing. There is no normal physiological process that can't be bastardized by the disease.

Nearly every one of the genes that turns out to be a key player in cancer has a vital role in the normal physiology of an organism. The genes that enable our brains and blood cells to develop are implicated in cancer.

Siddhartha Mukherjee Quotes