How Carcinogens Cause Cancer
Siddhartha Mukherjee is the author of The Emperor of All Maladies: A Biography of Cancer, winner of the 2011 Pulitzer Prize in general nonfiction, and The Laws of Medicine. He is the editor of Best Science Writing 2013. Mukherjee is an assistant professor of medicine at Columbia University and a cancer physician and researcher. A Rhodes scholar, he graduated from Stanford University, University of Oxford, and Harvard Medical School. He has published articles in Nature, The New England Journal of Medicine, The New Yorker, The New York Times, and Cell. He lives in New York with his wife and daughters.
Siddhartha Mukherjee: So we’ve talked a little bit about the Cancer Genome. We’ve talked about the genetic changes, but I want to take one step back even before these genetic changes arise. Dr. Schwartzentruber, tell us what we know about how carcinogens cause cancer.
Doug Schwartzentruber: Well that is a challenging question because there are multiple ways for carcinogens to cause cancer and I probably should defer to some of the other panelists as well who have studied that much more than I have, but the obvious first step is how the environment which from the minute we’re born begins to interact and create feedback to say our normal cells that could then potentially be cancerous and maybe I'll stop at that point and lead into others.
Lewis Cantley: Well I can. I mean most carcinogens we think cause cancer by mutating DNA, but there are examples of carcinogens for example, forballesters [ph] which can cause skin cancers that almost certainly are to working through mutating DNA directly, although in the long run you always end up getting mutations in DNA. They are rather probably causing cells to grow at a higher rate and the higher the rate cells grow the more frequently they get mutations in DNA. Basically a cell has to go through a division cycle and make a daughter cell in order for a mutation to get locked in and that- But most really do it by directly damaging DNA, UV light, radiation directly damage the nucleotides in the DNA and many other chemical carcinogens interpolate into the DNA and at the time of cell division interfere with proper base replacement.
Harold Varmus: No, I agree entirely with this, but I would like to add two important points. First 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. Cancer is probably part of our heritage. Genetic change is a good thing at the species level because we generate diversity throughout living systems.
The other point I would make is that not all carcinogens are UV light or radiation. Some of them are viruses and it’s very important to keep that in mind. It has been estimated that in developing countries for example maybe a third of cancers are caused by viruses. We actually have vaccines that are effective against some of those viruses. The human papillomavirus vaccine, the human hepatitis B virus vaccine can prevent a very large amount of cancer in those countries if the vaccines are made available, brought to patients, made affordable in poor countries. Cervical cancer is largely controlled in this country by pap smears, by early detection, and we only have about 3,000 deaths a year in this country, but in many parts of the world, India for example, and large parts of Africa, cervical cancer is the most common cause of death from cancer among women, and we now have the potential to reduce the incidence of that cancer by two-thirds using the human papillomavirus vaccine.
Seemingly every year there are new reports that something we consume or use on a daily basis is carcinogenic. But what exactly does that mean on a biological level?
Being kind to others positively impacts your physical and mental health, according to this groundbreaking research by Stanford professor Dr. James Doty.
The default "rest mode" of our brains is often taken over by a "threat mode" setting because of our stressful, "on-the-go" lifestyles. When we are chronically in threat mode, this leaves us with less capacity for compassion.
- Showing compassion or acting kind to others can actually change your physiology, taking you out of threat mode and putting you back into your natural "rest and digest" mode.
- Research by a well-known Stanford professor Dr. James Doty has shown that acts of kindness or compassion that put us back into our "rest mode" can have lasting positive impacts on our physical and mental health.
Is information the fifth form of matter?
- Researchers have been trying for over 60 years to detect dark matter.
- There are many theories about it, but none are supported by evidence.
- The mass-energy-information equivalence principle combines several theories to offer an alternative to dark matter.
Establishing cultural rights to protect diverse groups may not be the answer.
- While it is good to recognize societal diversity, it is difficult to argue in favor of creating cultural accommodations to preserve and protect specific groups.
- Creating protections for people who belong to certain traditions can result in the creation of cultures that did not previously exist. The challenge would be to find a way to provide protections that are not too explicit while also being careful not to advantage one internal group and disadvantage another.
- The classical liberal response is a principle of hyper-tolerance. Groups are free to form, members are free to dissent, and there are no acknowledgements of special protections or of the right to force conformity within cultures.