Cancers are Genetic Mutations
What causes cancer? If I had to explain this in just a few words, I would say that cancer is caused by genetic mutations or alterations in your body's code. Every cell in your body contains a complete set of your genes. That's why we can clone things out of a single cell. A liver cell acts like a liver cell, yet it actually has your eye cell code in it as well. It's just quiet. In fact, I could get your complete DNA out of any single cell in your body.
The information in DNA is stored as a code made up of four chemicals: adenine (A), guanine (G), cytosine (C), and thymine (T). The chemicals form units called base pairs. In these units, A always pairs with T and C always pairs with G. If your DNA is altered, it’s like when a word is misspelled. This is a problem because DNA is basically the instruction manual that tells your cells how to function. It does this by sending a message through the RNA, which is basically a copy of the DNA. So if there’s a misspelling in your DNA, that will become a misspelling in the RNA. The RNA’s job is to pass information on to a protein. Proteins are the chemicals that do all the work inside the body, and if the RNA is carrying a misspelling, the protein will have a misspelling as well. This misspelling will cause the protein to misfire, which results in altered regulation of the cell. So when we speak of a genetic mutation, or alteration, we are speaking about something that has occurred because of a misspelling in the DNA.
As an example, I’ll discuss the epidermal growth factor receptor (EGFR). A receptor is a protein on the cell membrane, and EGFR is one of the receptors being targeted for the treatment of cancer.
EGFR is an important receptor in the body. There are several pathways that lead from this receptor to what we call the cell cycle, and EGFR is part of one of the pathways that gets the cell to crank along as it should. In other words, EGFR plays a role in how cells grow and divide. You need your cells to grow. Growth is not a bad thing—it's a good thing. But you also need your cells to stop growing, because the bad thing is uncontrolled growth. We’ll come back to EGFR shortly.