Breast cancer news, a lesson on genes and environment.

A day late, but I wanted to link to this post in Tara Parker-Pope’s Well Blog on First — the study Tara highlights is important, adding nuance (and difficulty) for women who discover they have certain mutations tied to very high probabilities of getting breast (and ovarian) cancer who try to interpret that knowledge.

As Tara writes, mutations in genes BRCA1 and BRCA2 had been viewed as almost certain indicators of cancers to come. Now, a report by a team at the Memorial Sloan Kettering found that the risks seem both to be somewhat lower than previously thought, and — this is the crucial bit — to vary significantly depending on other factors in different subgroups of patients.

The low end of the scale they observed was around a 36% chance of getting cancer by age 70 — still bad, from where I sit — but clearly a significantly different risk profile than the almost pure genetic determinism of the bad gene = cancer view.

(By the way, this is exactly the stuff that Masha Gessen deals with eloquently and in depth in her forthcoming book, Blood Matters, which I highly recommend when it goes on sale in April.)

Beyond the news itself, there is an important idea lurking in the background:  in their report, the authors suggest that other, still-unknown genetic differences, underlie the differences in outcomes for the women they observed in their study.

That is: the genomic environment of surrounding the known cancer-implicated genes is what they believe shapes whether and when BRCA1 and 2 mutations lead to disease in a given patient

John Maynard Smith, one of the less publicly celebrated great biologists of the 20th century, emphasized the importance of this kind of finding  when I had the good fortune to interview him a few years ago.  He demanded that I understand that the environment for a gene begins with the chromosome on which it finds itself, and then broadens out to include the rest of the genome in which it lies, and then on out from there. What happens in the molecular environment of the gene is crucial, both in regulating the normal interaction between different genes and non-coding bits of DNA, or when some variation or derangement of normal function affects the action of any given gene.

That subtlety gets lost, often, when genetics hits the public square.  See, for example, Lucky Jim Watson genes-and-IQ skirmishes of late last year.  It’s easy for both researcher and reporter to fall into a kind of naive genetic determinism. One looks for the gene for some trait or disease; one reports that the gene for a given problem has been found — and then later, sometimes years later, it becomes clear that whatever is going cannot be that simple.

John Maynard Smith was very elderly when I met him, and had seen a lot, the entire modern history of genetics, from the double helix on. He knew better. It’s an important lesson to remember.

Image: Charles Alston, “Modern Medicine.” Location: Harlem Hospital. The work was commissioned by the US Government and is hence public domain. Source: Wikipedia Commons.

Explore posts in the same categories: Cancer, genes, genetics, good books, Medicine

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