Scientists discover 'transmissible cancers' spreading among shellfish

Tuesday, July 05, 2016 by: Daniel Barker
Tags: shellfish, transmissible cancer, infectious disease

---

(NaturalNews) A new study has found "transmissible cancers" among shellfish, disproving previous beliefs that such occurrences are rare in nature, and raising questions regarding the implications for humans.

Cases of transmissible cancer had until recently only been observed in two mammal species, but researchers from Columbia University Medical Center in New York have discovered that shellfish are also capable of spreading cancer.

From Live Science:

"Although cancer can spread to distant parts of a body, in an often-deadly process known as metastasis, it generally stays within the individual in which it originated. Recently, however, scientists discovered that cancer cells can sometimes escape an organism and spread to others. These cells are clones that are nearly identical to the originals, save for mutations that might have popped up since they diverged from the initial cancer cells.

"For years, transmissible cancers were seen only in two mammal species — dogs and Tasmanian devils — which suggested that they might be rare in nature. However, in 2015, researchers discovered transmissible cancers in soft-shell clams, suggesting that such infections might be more widespread than previously thought."

Transmissible tumors found in three bivalve species

The researchers found tumors among clams, mussels and cockles from Spain and Canada, that had originated in other individual specimens. In other words, the cancer had somehow spread through the environment from individual to individual, and did not match the genetic makeup of their hosts.

From the study:

"Our results indicate that transmission of contagious cancer cells is a widespread phenomenon in the marine environment, with multiple independent lineages developing in multiple species. Cases of transmissible cancer appear to outnumber spontaneous disease, at least in the species investigated so far."

The team also found "one example of cross-species transmission:"

"These transmissible cancers constitute a distinct class of infectious agent and show the remarkable ability of tumours to acquire new phenotypes [genetic types] that promote their own survival and propagation."

Professor Stephen Goff, one of the researchers involved in the study, told The Independent that the results had caused him to think differently about marine environments.

"It's interesting to note that the ocean is a sea of various bacteria and now [cancer] cells that are capable of being pathogens," he said. "I guess it's a kind of change of thinking, that there are contagious cells floating around in the sea that can colonise a susceptible host."

The researchers say that they will study the genetic processes involved in the transference of tumors from one creature to another, in hopes of learning more about how cancer spreads in humans.

Implications for humans?

Although the researchers say the findings should not discourage people from eating shellfish or venturing into the ocean, there are concerns transmissible cancers could become an issue for humans.

In a commentary on the research findings, Dr. Elizabeth Murchison of Cambridge University, wrote:

"The potential for cancer cells to become free-living infectious agents raises questions about the implications for cancer transmission in humans.

"It is possible that, like the canine transmissible cancer, these cancers are ancient cell lineages that have co-evolved with their hosts through the millennia; or perhaps their emergence is a relatively recent occurrence, possibly stimulated by infectious agents, environmental changes, aquaculture or other anthropogenic [human] activities."

Scientists aren't sure whether contagious cancer cells are a recent development, or if they've been around all along. Either way, the implications are rather disturbing, to say the least.

If you need some reassuring words at this point, however, I'll leave you with the comments of Professor Mel Greaves, director of the Centre of Evolution and Cancer at The Institute for Cancer Research in London, who said the findings are "no cause for concern:"

"In all three cases, transmission was possible because a blood route for cancer cells was available and the immune system was compromised. This risk is very, very small indeed. Regarding these new results in shellfish, the public should not be at all alarmed as the processes involved are different from those in people.

"The biology is, however, very interesting with implications for the evolution of both cancer cell clones and immune recognition within and between species."

Thanks, professor; I'm sure we all feel better now. ...

Sources:

LiveScience.com

Nature.com

Independent.co.uk

Science.NaturalNews.com