Horizon, Host: Ted Simons

March 23, 2011


Host: Ted Simons

Cancer Ancestor


  • ASU researcher Paul Davies shares his theory about cancer being our evolutionary ancestor.
Guests:
  • Paul Davies - ASU researcher
Category: Science

View Transcript
Ted Simons: There's a controversial new theory about cancer. It suggests that cancer cellars living fossils that the remnants of an evolutionary stage where animals started learning control of cellular reproduction. Arizona State astrobiologist Paul Davies is one of two researchers proposing the theory. He joins us to tell us more about it.

Paul Davies: Thank you.

Ted Simons: Cancer could be our oldest ancestors? Explain, please.

Paul Davies: Well, I think everybody is familiar with the fact that life on earth began very simple, just single cells. And this went on for a long time. But then about 600 million years ago suddenly there was a great flowering of multicellular life. It's often called the Cambrian explosion but it didn't happen overnight. There was a period of maybe a billion years preceding that where cells began to get together and cooperate into rudimentary colonies. These rudimentary colonies were like the earliest tumors. These tumors represent a throw back to that time about 1 billion years ago where that first experimentation.

Ted Simons: This is when these cells kind of get some control over reproduction? You mentioned -- just some sort of what cooperation?

Paul Davies: Cooperation is the word. You see, because single cells have just one imperative -- replicate, replicate, replicate. But when cells began to get together to form colonies and cooperative arrangements, they had to relinquish some of their rights and one of these rights is the right to replicate when you want to. And so now, in our bodies, all this is very tightly controlled. Skin cell, for example, it can't just decide to replicate. It has to wait for a message to tell it to do so. The same with liver cell, lung cells and so on. If that cooperative arrangements breaks downs, cancer results. What we are saying is not that this is just cells gone wrong. It's cells reverting to the way they used to be a billion years ago.

Ted Simons: So would this be, the cancer cells of today, distant relatives of these earlier cells? Is this a stable genetic makeup, same as then? Same as now?

Paul Davies: What we are saying is there is a set of Gene, a tool kit if you like of Gene, very ancient genes that know how to build these rudimentary cancerous colonies and these are overlaid by more sophisticated ones that represent life as we now see it with the very many different cell types, and different organs and so on. And when something goes wrong, it springs its ancient tool kit of genes and comes that earlier wave doing things. It's like you mention a painting that is painted over with something else. And something begins to erase the surface painting and exposes the one that lies underneath, the more ancient one. That's what we are saying that something is exposing that tool kit of ancient genes which is why cancer seems to be such a formidable foe. It doesn't seem like something just going wrong. It seems like something is going right, a preprogrammed response.

Ted Simons: An interested way to look at it and yet something so destructive. For this long a period of time, wouldn't that have phased itself out? I mean, why does this particular dynamic survive?

Paul Davies: That's because the genes that we are talking about are not used. It's not that they no longer needed. They are needed, for example, during embryo development. When an embryo develops it goes all through the stages life has gone through over evolutionary history. For example, the human embryo goes to a stage where there are gills, web feet and tails and they get sort of suppressed later on. Although occasionally people will be born with a tail, for example. That’s called an atavism. We are saying that cancer is a type of ATAVISM where these ancient genes still have uses but in the adult form are all suppressed. Spring out again.

Ted Simons: You mentioned spring out. A lot of folks think of cancer, they think of cancer cells just going crazy as attacking the body in ways that don't make any sense, no form, no fashion. They are all over the place. How does that work with the idea they cooperate? And they know what they are doing.

Paul Davies: They do. And there's some very striking examples. One of these is called the soil and seed hypothesis. It's been around for about 100 years. The idea when cancer spreads around the body it doesn't do so randomly. That they are certainly organs that the cancer cells are directed to, and they make a home in them. And there's now very good evidence that a primary tumor will send out chemical signals to prepare the ground, prepare the soil. It's almost like sending out bags of fertilizer ahead of the cancer cells. So this is a cooperative response. This is not just cells going hay wire.

Ted Simons: So let me get this straight. If they are ancestors, going back that kind of time, the genetic makeup should be somewhat stable. If it is somewhat stable, shouldn't there be a way to target? Shouldn't there be less --

Paul Davies: That’s the good news. The good news is that when cancer breaks out in somebody's body, it's not evolving randomly. It's not just trying all the tricks available. There is, of course, some random change. But this is a preprogrammed response of a set of very ancient genes which are already there which have come out and then the reason the cancer cells can deploy so many wonderful tricks, wonderful for them, terrible for the patient but so many amazing survival properties because these are tried and tested survival strategies for a long time ago. But there's a limited number. This isn't just random. This is a targeted type of response. So we can target those genes if we begin to understand how this tool kit works. We can target that and it means that there's far more chance that we can bring this under control than you would believe from the conventional theory.

Ted Simons: So basically if I understand you correctly what you are saying is figure out, go back to your painting, figure out what causes the scratch. Figure out what triggers the scratch.

Paul Davies: Right.

Ted Simons: You have cancer pretty much figured snout.

Paul Davies: Well, that's a way of preventing cancer. What we are saying if you understand the painting underneath then we are the chance of being able to control it. My feeling about cancer is that we should forget about cures. We should just think in terms of controlling. Because these are your body's own cells. It's just they are not behaving in a way that is good for the individual. And so rather than thinking, well, we have to exterminate or eliminate them, these are genes that are deeply embedded in our genome and if we know what they are and we can understand them better, we can come to understand them better by studying other organisms. We have to study the history of life on earth. Every multicellular organism gets cancer. How ancient are these genes? How did they evolve? And then when we got that broader picture, we are in a much better chance of controlling it.

Ted Simons: What's your reaction, what kind of reaction, I should say, are you getting from this idea?

Paul Davies: Oh, mixture of good and bad. Some people have been studying the evolution of cancer cells in the body, and they have just taken sort of straight forward Darwinian approach, random and hope for the best. And those people are actually quite receptive to these ideas because it builds off their own ideas. And some people think who are these guys? I came to the subject wearing my astrobiology hat so we are interested in life in the universe, the history of life on earth. This is not a one O-way street. Astrobiology can inform cancer biology but cancer biology can inform astrobiology. It tells us something about the nature of life itself.

Ted Simons: Real quickly what's the next evolution for this kind of thinking, this theory and thought?

Paul Davies: What I am going to do is bring together embryologists who people who understand early embryo development and lend their insights into what's going on in the various early stages of the embryo and see if we can put that together with the astrobiology and with the cancer biology and come up with a way of, after all, at the end of the day, we want therapeutic outcomes is what we want.

Ted Simons: Thank you so much for joining us. We appreciate it.

Paul Davies My pleasure.

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