Breast Cancer, Genes, and Jews

I gave a talk the other day at the Jewish Community Center of Virginia Beach/Norfolk, where they were having a sort of fair observing Breast Cancer Awareness month. It seemed a little anomalous, with scores of children roaming their huge back yard running races and eating cotton candy, teenagers off in corners chatting about their secret and public lives, a local talent show, pink t-shirts everywhere, and the author of The Jewish Body speaking about breast cancer and the Jews.

The people who invited me knew that I had lost my first wife to this terrible disease, and so they asked me to talk about the state of the art in breast cancer treatment and about the Jewish angle in particular, with an emphasis on genes, and with a personal touch. I tried to do all that, and wrote about the general and personal dimensions on my other website.

But what does it have to do with the Jews?

There is an increasing perception that Jewish women have more breast cancer than others, but this has not been shown. Once you control for reproductive life, you find no differences. But because Jewish women (like most educated upper middle class women) start childbearing late, have few children, and don’t breast feed for very long, they are more vulnerable.

The perception that this disease is somehow Jewish arises from the genes that help cause it, some of which are indeed more common in Jews. The first two genes discovered to play a specific role in breast cancer are the BRCA genes (often pronounced “bracka”), which are tumor suppressor genes. They aren’t restricted to Jews, but they are more common in Ashkenazic Jews than in others.

Both sexes have them and can pass them on to their children, but women are 100 times more susceptible to breast cancer than men—one in eight women will get it at some point in life–and the BRCA genes cause cancer of the ovary as well as the breast. Any one of a number of different mutations in either of them will reduce your ability to suppress a tumor (microscopic ones pop up in all of us) and increase your chances of cancer.

The way it works is, you inherit one BRCA mutation in one of a pair of chromosomes. That doesn’t lead straight to the cancer. But all cells in your body, including the ones in the lining of the milk glands, have this mutation, and when radiation or toxins or just the bad luck of DNA damage when the cell divides leads to a mirror-image mutation in the other chromosome of the pair, that cell will be able to divide much more easily, and give you the runaway growth that is cancer.

So why the Jews? Like the genes for Tay-Sachs Disease (a form of mental retardation leading to early death) and several other nervous system diseases, Ashkenazic Jews are more likely to have the BRCA genes. They are a lot less the “property” of Ashkenazic Jews than the Tay-Sachs genes, but their particular form of hereditary cancer is more Jewish than not.

And this leads to some questions about how the Ashkenazic Jews got them. The consensus is that Ashkenazim—eighty percent of the world’s Jews today—arose from a very small “founder” population, and may have experienced other “bottlenecks” in their history when plagues shrank the population to a small size again. Also, the strong desire to marry other Jews kept any genes that randomly appeared within the population.

But there is a new theory about Ashkenazic diseases that goes beyond the idea of genetic isolation. It was put forward in the Journal of Biosocial Science in 2006 and has caused a lot of controversy. The authors are not Jewish—they are Gregory Cochran, Jason Hardy, and my old friend Henry Harpending—so (as we say in Georgia) they don’t have a dog in the fight.

In a nutshell, they argue that there has been selection for high intelligence in Ashkenazic Jews throughout their history, and that this selection has sort of “dragged along” the genetic diseases, the way resistance to malaria “dragged along” sickle cell anemia. Carriers for the sickle gene resist malaria better, and the theory is that some forms of the Ashkenazic disease genes promote brain development in early life.

This is far from proven, but there are arguments. First, Ashkenazic Jews have higher average IQs in many studies, and with 0.2 percent of the world’s population have won over 20 percent of the Nobel prizes in science. Second, all the Ashkenazic genes affect just a few of the body’s physiological pathways, and these seem to be also implicated in brain development.

In the case of the BRCA genes, laboratory experiments with embryonic rat brain cells show that normal versions of the genes suppress brain cell growth just as they later suppress tumors. This means a mutation could cause both added brain development and cancer. A lot more research is needed before we conclude that this is true, but one thing is certain. Jewish genes–for better or for worse–are once again a legitimate subject of scientific discussion, and we have to deal with it.