Are sick steamer clams giving each other cancer?
Can you “catch” cancer from someone else with cancer, like catching a cold from a co-worker who is hacking and sneezing right next to you?
No, not if you’re a human. But if you’re a steamer clam, the answer is yes.
In April, biologist Carol Reinisch and her fellow researchers from Columbia University and Environment Canada published a report in the scientific journal Cell on the cause of a leukemia-like disease spread through clam beds on the East Coast.
The researchers discovered that the clams were not infected by exposure to a virus or a chemical carcinogen, but by cancer cells released from other sick clams.
Reinisch said the free-floating cells apparently survive long enough in seawater to be sucked in by a neighboring healthy clam, thereby infecting it.
Cancers typically grow from a host’s tissue. But analysis of the leukemia cells from different clams showed that they were nearly identical and did not share their hosts’ individual genetic makeup.
Simply put, the leukemia cells were foreign intruders that were practically clones of each other. This led researchers to theorize that the leukemia originated as a mutation in a cell of a single clam and has since spread.
Reinisch first encountered the sick clams in the 1970s, when she worked as a researcher at Marine Biological Laboratory in Woods Hole.
She found diseased clams along the eastern seaboard, from the coastal waters off Canada’s Prince Edward Island to the Carolinas, the southern extent of the clam’s habitat.
The problem was particularly prevalent in areas polluted by agricultural runoff or industrial chemicals, such as New Bedford Harbor in Massachusetts, she said.
The clams in New Bedford had been contaminated with PCBs, and the areas of contamination and infected clams coincided. “We knew where to find them,” Reinisch said, adding that the harbor is now “far, far better.”
Contagious and cancer aren’t words often used together. In fact, Reinisch said, there are only two other cancers known in the world that are transmitted by cancer cells from one host to another. One is a venereal cancer in dogs; the other causes facial tumors in Tasmanian Devils and is spread by biting.
What about the danger of eating infected steamer clams, which are also used for fried clams?
“No, no,” she said of any risk, adding that soft-shell clams are always cooked before they’re consumed. Reinisch said she eats steamer clams, and “I don’t have a death wish.”