Episode Details

Russ Altman: Today on The Future of Everything, the future of detecting DNA in your blood.

Now DNA is the building block of life. It is a relatively simple long molecule or polymer made out of four components or DNA bases which have one letter abbreviations, the famous ATCG, which stand for their chemical names. It’s like a string of beans, beads, beads, but it is long. A human genome is made of about three billion DNA bases, divided into 23 chromosomes. So if you add up the beads in each chromosome, you get about three billion. You get a genome from mom and you get one from dad. So you have two copies of the genome, mostly the same but obviously not identical, or six billion total.

Now DNA contains the blueprints for how your cells live, how they grow, how they interact with other cells, and like a computer program, it allows the cell to perform simple computations to make decisions about when and where things happen.

If this goes wrong, you can get cancer. Mutations in the DNA cause the computations and decisions to go wrong.

Other things can happen too. In the last ten years, researchers have learned that they can detect DNA in the blood. Now we knew that the cells in the blood had DNA, so that was not surprising, but what was surprising is that there is sometimes DNA from other cells in the body, often cells that have died and just released their DNA into the bloodstream. This is sometimes called cell-free DNA because it is floating in the blood and it’s not really part of a cell. Although this may seem like it’s junk, it offers evidence of lots of other processes going on in the body, processes diverse as cancer, pregnancy, stress on organs, or even death and many others.

Dr. Stephen Quake is a professor of Bioengineering, Applied Physics and Physics and Stanford University. Steve pioneered the detection of DNA in the blood and some its first applications.

Steve, what drove your interest in detecting DNA, and what was the first demonstration that this would actually be useful?

Stephen Quake: Well, my interest came actually when I became a father. My wife and I were in to see the doctor, and the doctor says you guys should think about getting amniocentesis. And it was seemed like a theoretical question and something we have time to think about. We said yeah, okay, that sounds like the right thing if recommending it.

Russ Altman: And this is a super risky procedure in many ways. A needle goes into the uterus near the baby to extract fluids.

Stephen Quake: Big needle right in the mom’s belly, right next to the fetus to try to grab a few cells, and so to do genetic testing. And we said yeah, it sounds like a good idea, thinking we schedule another appointment for it. Next thing we knew, the guy was turning around with a giant needle, plunges it right into my wife’s belly,

Russ Altman: Whoa.

Stephen Quake: Yeah, whoa, exactly. That was our response. And it’s the response of many people who undergo that certain invasive testing. And not surprisingly, there’s risk associated with doing that testing. Sometimes, you lose the baby and other health problems that might happen.

Russ Altman: How far into the pregnancy were you?

Stephen Quake: That’s typically done, I don’t know, around 14 weeks, something like that, 15 weeks, somewhere around there. And so that sensitized me to holy cow, there’s a problem here that you’re asking a diagnostic question, and there’s a lot of risk associated with it. And so I began to think are there ways to ask these genetic questions and do diagnostics without adding risk? And I eventually stumbled upon this old scientific literature about this cell-free DNA that you were mentioning, which, as it turns out, was first discovered as a phenomenon in 1948.

Russ Altman: That’s before Watson and Crick even articulated the importance of DNA for genetics.

Stephen Quake: It’s before the structure, and it’s before people k