Breast cancer odds of recovery differ for left breast v. right breast
Very interesting article in Quanta by Tim Vernimmen:
In 2009, after she was diagnosed with stage 3 breast cancer, Ann Ramsdellbegan to search the scientific literature to see if someone with her diagnosis could make a full recovery. Ramsdell, a developmental biologist at the University of South Carolina, soon found something strange: The odds of recovery differed for women who had cancer in the left breast versus the right. Even more surprisingly, she found research suggesting that women with asymmetric breast tissue are more likely to develop cancer.
Asymmetry is not readily apparent. Yet below the skin, asymmetric structures are common. Consider how our gut winds its way through the abdominal cavity, sprouting unpaired organs as it goes. Or how our heart, born from two identical structures fused together, twists itself into an asymmetrical pump that can simultaneously push oxygen-rich blood around the body and draw in a new swig from the lungs, all in a heartbeat. The body’s natural asymmetry is crucially important to our well-being. But, as Ramsdell knew, it was all too often ignored.
In her early years as a scientist, Ramsdell never gave asymmetry much thought. But on the day of her dissertation defense, she put a borrowed slide into a projector (this in the days before PowerPoint). The slide was of a chick embryo at the stage where its heart begins to loop to one side. Afterward a colleague asked why she put the slide in backward. “It’s an embarrassing story,” she said, “but I had never even thought about the directionality of heart looping.” The chick’s developing heart could distinguish between left and right, same as ours. She went on to do her postdoctoral research on why the heart loops to one side.
Years later, after her recovery, Ramsdell decided to leave the heart behind and to start looking for asymmetry in the mammary glands of mammals. In marsupials like wallabies and kangaroos, she read, the left and the right glands produce a different kind of milk, geared toward offspring of different ages. But her initial studies of mice proved disappointing — their left and right mammary glands didn’t seem to differ at all.
Then she zoomed in on the genes and proteins that are active in different cells of the breast. There she found strong differences. The left breast, which appears to be more prone to cancer, also tends to have a higher number of unspecialized cells, according to unpublished work that’s undergoing peer review. Those allow the breast to repair damaged tissue, but since they have a higher capacity to divide, they can also be involved in tumor formation. Why the cells are more common on the left, Ramsdell has not yet figured out. “But we think it has to do with the embryonic environment the cells grow up in, which is quite different on both sides.”
Ramsdell and a cadre of other developmental biologists are trying to unravel why the organisms can tell their right from left. . .