How Do Carcinogens Cause Cancer?

What do processed meats, diet sodas, tobacco, tanning beds, and plastics all have in common? They are all known or suspected to be carcinogens, substances which promote the genetic mutations that lead to cancer. During Big Think's recent panel discussion on cancer research and treatment, five leading experts talked about the many ways that carcinogens can disrupt your DNA. 

In order to understand how carcinogens work, it is important to first have some perspective on what cancer is. Unlike foreign pathogens or diseases that attack the body from without, cancer results from an error in the natural cell division process. In fact, "cancer is probably part of our heritage," says Harold Varmus, Director of the National Cancer Institute:

"We as individuals grow up from a single cell and through many, many rounds of cell division, many errors are going to occur because the ability to copy and distribute the three billion base pairs of DNA into daughter cells is an inherently error prone mechanism. We have ways to try to correct it, but nevertheless damage will occur and over the course of many cell doublings there will be damage that can be carcinogenic, so you don’t need to have external factors for cancer to arise."

That said, carcinogens like asbestos or UV rays, these external factors Varmus describes above, do make DNA mutations—and thus cancer—more likely to occur. They can give rise to cancers essentially in one of three ways: they can, like UV rays or radiation, directly cause genetic mutations or they can cause cells to divide much more rapidly, amplifying the normal rate of error inherent to cell division, says Lewis Cantley. It is also important to remember, says Varmus, that viruses can cause certain cancers, like cervical cancer. Vaccines that are effective against some of these viruses exist, but access is a problem, especially in the developing world, where it's estimated that a third of all cancers are caused by viruses. Cervical cancer, for instance, only causes 3,000 deaths a year in the United States thanks to pap smears and early detection, but in many parts of the world including India and parts of Africa, it is the leading cause of death from cancer among women. 

Learn More:

—The U.S. Department of Health and Human Service's 11th Report on Carcinogens

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