IRA FLATOW, host:
This is TALK OF THE NATION: SCIENCE FRIDAY. I'm Ira Flatow.
A bit later in the hour: technology and global warming. But first, in the mid-1990s, there was a quiet revolution in breast cancer research. Scientists found two genes - BRCA1, BRCA2 - that if they had certain mutations dramatically increase the risk of breast cancer. Now, there are a handful of other genes that can be tested for as well.
But this week, in papers and the journals Nature and Nature Genetics, several teams from around the world report the discovery of six areas in the genome that they believe to be linked to breast cancer. Those don't increase the risk of cancer nearly as much as the BRCA1 or two genes, but the researchers say that these regions may be found in many more women.
Joining me now is Doctor David Hunter. He is lead author of one of the papers and a co-author of another. He's professor of cancer prevention at Harvard School of Public Health and epidemiologist at Brigham and Women's Hospital in Boston. He joins us by phone from a conference in Albuquerque. Thank you for taking time from the conference to be with us, Dr. Hunter.
Doctor DAVID HUNTER (Cancer Prevention Professor, Harvard School of Public Health; Epidemiologist, Brigham and Women's Hospital): Thank you. Glad to be with you.
FLATOW: Well, then, tell us exactly what you found. These are not genes from cells per se, are they?
Dr. HUNTER: Well, some of them variance in genes, some of them genetic regions that we use new technologies to scan the human genome for inherited variants that are associated with increased risk of breast cancer. And we identified some strong associations and confirmed one of these in three additional studies. The other groups concern additional genetic regions and the variance in those genes associated with breast cancer risk.
FLATOW: And so what - what use do you make of this finding now?
Dr. HUNTER: So at this point, I think the key thing to know is that there'll be more findings soon. We're using a new generation of technology that's been (unintelligible) by The Human Genome Project and the human (unintelligible) type map project that defines genetic variation around the world.
And these new technologies allow us to look at gene variants that convey much lower degrees of risk than BRCA1 and BRCA2, which are the classic, very high-risk genes. And so, this is really the first reports of probably a series of reports as we really access these lower-risk genes for the first time.
FLATOW: So are you saying you have a more sensitive task that brings out other risky genes that we might not have seen before?
Dr. HUNTER: That's correct. It's basically - what we had to before was essentially look in families in which there was a very, very high burden of breast cancer. So by definition, the risks had to be very high for the variance from those genes in order to create those families with a very high burden. But most women with breast cancer either don't have a family history or just had a single family member who's been diagnosed with breast cancer and don't come from these very high-risk families.
So the new generation of technology allows us to look at more than 500,000 variants across the genome and detect the location of these gene variants by screening thousands of women with breast cancer and thousands of women without breast cancer, but those women don't necessarily have to have a strong family history.
FLATOW: 1-800 - 1-800-989-8255 is our number. Talking with David Hunter. Can you then theoretically continue screening and find even more variants that way?
Dr. HUNTER: Almost certainly we will. These papers are really the first fruits of this new approach, and in our own study, we're actually calling deeper through the initial scan. We're taking large numbers of gene variants that are, well, weakly associated with breast cancer in the initial scan, seeing if they are associated in large studies. And it's very, very likely that there'll be more of these lower-risk variants discovered in the next months and years.
FLATOW: You mentioned briefly about comparing them to the BRCA1 and two genes that really produced a significant increase in the risk of breast cancer. Can you give me an idea of one - something that you found - and compare it to the - to how they might compare to those two genes?
Dr. HUNTER: Sure. So the variants that we found were in the gene called FGFR2, Fiber Glass Growth Factor Receptor 2, which wasn't really a gene that had been previously associated with at least inherited risk of breast cancer. And the risk variance there that we find are associated with about a 20-percent increase in risk if a woman carries a single copy and about a 60-percent increase in risk if a women carries two copies.
And that compares with BRCA1 and BRCA2, where the risk increases more like 2,000 percent. So, we're comparing sort of a 1.5 fold here with 20 fold plus with the BRCA1 and the BRCA2. The big difference is that the mutations that increase the risk of breast cancer in BRCA1 and BCA2 fortunately is fairly rare in the population. Less than one percent of the women in U.S. carry mutations on those genes, whereas now, we're finding genetic variants that actually the majority of women carry, but they give rise to a much more modest increase in risk.
FLATOW: Did that give you - does that make you feel better that you find more of these variants in women, or does it make you feel worse that there might be more women at risk?
Dr. HUNTER: Well, you know, we've known that breast cancer is a very common disease. About 11 percent of women will be diagnosed with breast cancer in their lifetime. So it's been very frustrating that through BRCA1, BRCA2, these very high-risk genes, we've only been able to explain a very small fraction of breast cancer risk. So this gives me hope that we're going to understand a much, much bigger piece of the inherited risk of breast cancer. And if we do that, we understand more about the mechanisms of beast cancer, and that may lead to better means of prevention and potentially treatments.
FLATOW: At - at what point do doctors start, then, screening women for these other kinds of risk?
Dr. HUNTER: Not yet - for two reasons. I think there'll be more variants soon, and it's only once we have the complete list of variants that we'll really be able to sensibly put them all on the table and work out which variants it would make sense to screen for in which combinations. That may only be two or three years away, but we're not there yet.
The other reason is that we very rarely screen for risk of disease if there's no advise we can give that will then ameliorate that risk or alter that risk. And the real challenge here is, as we understand how better to sort out high from medium from lower risk for breast cancer - and in fact all common diseases - the real challenge is going to be then working out what advice we can give to allow people who are at high risk to reduce that risk, and that will require maybe several more years before we're really confident that we've got good evidence to give that advice.
FLATOW: Penny in Redding, California. Hi, welcome to SCIENCE FRIDAY.
PENNY (Caller): Hi. Thank you for taking my call. I'm a registered nurse, and I've been working in the field for, like, 35 years. I recently took a course on oncology, and I have this wonderful little oncology nursing guidebook, and it says that breast cancer - the highest incidence was in Alamino County(ph) in the Bay Area and the second was Hawaii. And thinking what they might have in common is, like, World War II or a Navy chemical exposure.
And I know they aren't testing people for how much exposures they get to these chemicals, and if they're in the air. And when I look at this book and I look under associated risk factors for all kinds of cancers, it's talking about vinyl chlorides, it's talking about I - you know, like radiation exposure, and nobody seems to want to talk about that. And I was wondering, you know, why that is, because my idea of how the genes work is that the genes are either turned on or turned off by what we're not quite sure. But, you know, it sounds like - by looking at this book - that it's chemical exposure that's doing it.
FLATOW: Dr. Hunter?
Dr. HUNTER: I think that that's a really good point. I mean, we know that environment and lifestyle are tremendously important for breast cancer and other diseases, and the data you refer to, which shows that in certain parts of the country, breast cancer rates are higher than other parts of the country has been a very, very active focus of research - the possibility exists that some of the pollution exposures that you refer to are maybe associated with breast cancer, but it's been very, very difficult to prove.
And some of those geographic variabilities and risks have been shown to be due to different patterns of breast cancer risk factors that we do understand, like the age which a woman has her first child, the number of children, obesity, alcohol consumption. Those do vary around the country, and they do explain a substantial proportion of the geographic variability in breast cancer rates but not all.
FLATOW: Thank you for calling, Penny.
1-800-989-8255. Is it appearing, as we - as we're able to probe the genome more and more, that cancers are having specific genes for certain cancers rather than, you know, a general gene for a lot of different cancers?
Dr. HUNTER: That's pretty much what we're finding, and that raises a whole series of fascinating questions about why these gene variants are so organ-specific and may give us insight into the genesis of cancers at specific sites.
FLATOW: Is it true that only 10 percent of all breast cancers are caused by genetic components?
Dr. HUNTER: Well, that's the estimate for the - that's the upper end of the estimate for the, sort of, high-risk genes where there's a strong or at least present family history. The twin studies suggest that the proportion that's due to inherited genetic variation actually might be substantially higher and up to about 50 percent. But most of that risk is going to turn out to be these common but low-risk alleles, of which there may turn out to be before we're done…
Dr. HUNTER: …dozens, potentially even hundreds.
FLATOW: So when you say before you're done, is that where you're headed next? Is that where you take this research?
Dr. HUNTER: Exactly. So our group working with National Cancer Institute and the other groups internationally are really very well organized now to use these new technologies to comb through the genome to find these variants that are associated with these more modest degrees of risk. And then there's a whole other set of research opportunities. Basically, what's happening is that genes that we have no idea had really anything to do with cancer risks turn out to be involved. So we're very hopeful that this can open up whole new avenues of research into the causes of cancer.
FLATOW: Well, Dr. Hunter, I want to thank you very much for taking time out of your busy week to talk with us.
Dr. HUNTER: Thank you for having me on your show.
FLATOW: And good luck to you.
Dr. HUNTER: Thanks a lot.
FLATOW: David Hunter is a professor of cancer prevention at the Harvard School of Public Health, and epidemiologist at the Brigham and Women's Hospital in Boston.
We're going to take a break and when we come back, we're going to talk about a new technology, a new way to reduce greenhouse gas emissions. We're going to talk about someone who is developing a technique to suck CO2 right out of the air like a vacuum cleaner. It's being developed now, and maybe that's how we can reduce CO2 levels. Just put this up around. We'll talk about it. Get your phone calls, our number 1-800-989-8255. Stay with us. We'll be right back.
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FLATOW: I'm Ira Flatow. This is TALK OF THE NATION: SCIENCE FRIDAY from NPR News.
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