A Genetic Disease
Why is cancer called a genetic disease if it isn't inherited? Cancer results, as I said, from alterations in the DNA in your genes. This is what makes it a genetic disease. These alterations, in turn, contribute to the development of the six common characteristics that I just reviewed. When we examine DNA from tumor cells, we consistently find these mutations, no matter what type of cancer you have.
When we examine DNA to look for mutations, it is just like using spell check. Literally, we take your cells, pull out the DNA from the nucleus, and put it into a machine which knows how the letters A, T, C and G in the DNA should be and which can find the misspellings, or genetic mutations, that could interfere with your cell cycle. When you put a cancer cell into the spell-check machine there is always a genetic mutation. In fact, there are usually many genetic mutations because cancer is really an accumulation of a number of mutations. There is no single mutation that is able to create all six hallmarks of cancer. It's an amazing number of different mutations, and it is this accumulation of mutations in cells over time that underlines the formation of cancer or carcinogenesis.
This also explains why there's an increased incidence of cancer as we get older, and as people are living longer because they are not dying of other diseases like polio and tuberculosis. Yes, the environment plays a role, no question about it. We've gone from a million years of being a farming and hunting society to an industrial society for the last 100 years. Our DNA can't adapt that quickly, and as we live longer and these mutations accumulate, cancer incidence rises.