Seas and oceans are full of tiny organisms such as fungi, algae and bacteria, but also cancer cells. As strange as this may seem in some types of cancer, tumor cells behave like parasites that can be transmitted directly between individuals.
Although the contagion of this disease is somewhat unusual, as it occurs in dogs or Tasmanian devils , transmissible cancers can be common under the sea. And in these cases it is marine bivalves such as clams , cockles and mussels that can infect a type of blood cancer, similar to leukemia , called hemic neoplasia , which is characterized by the uncontrolled proliferation of blood-like cells.
Tumor cells behave like parasites that can be transmitted directly between bivalve individuals
When this happens, these cancer cells can leave the host that generated them and live in the marine environment until they infect a new host. A new study, published in the journal eLife , shows that it can even spread through the different bivalve species.
To do this, the European project Scuba Cancers , in which the group Genomes and Disease of CiMUS participate of the University of Santiago de Compostela and other researchers from Portugal, France, Ireland and Croatia, has made it possible to analyze the prevalence of this disease in the species Venus verrucosa , known as almejón, found on the Atlantic coast of Europe and the Mediterranean Sea.
Scientists collected more than 500 clam specimens at eight sampling points in five European countries, including Spain ( Galicia and [ 19459002] Balearic Islands ). The results confirm that this contagious blood cancer spread between clams living in the Atlantic Ocean and the Mediterranean Sea by jumping from one species of clam to another.
From one sea to another from species to species
DNA sequencing technologies have made it possible to discover that cancer cells of the original species “can jump between species behaving in an infectious way”, points out the CiMUS researcher, Alicia L. Bruzos . Thus the cancer originated in a single clam, subsequently became infectious and spread among the clams V. verrucosa .
DNA sequencing technologies have made it possible to discover that cancer cells of the original species can jump between species behaving infectiously
The cancer contained genetic sequences from both the clam and another species of clam, which was identified as a clam, Chamelea gallina .
Thus, the study of DNA, both nuclear and mitochondrial, revealed that this cancer originated in a clam ‘ donor ‘ that inhabits the same regions as the first clams ‘ [ 19459002] receivers ‘. According to the researchers, the spread of cancer between closely related species therefore alerts us to the danger posed by these contagious cancers.
“As this may pose a potential threat to marine ecology , we need to continue studying and controlling pathogens , including cancers, to help protect these species ”, indicates the main author, José Tubío , researcher of Genomes and Diseases at USC.
How could cancer cells get so far?
The results add to the evidence that cancers can spread between different mollusk species and suggest that human activities may be inadvertently contributing to the spread of these cancers to new places and species.
Scientists suggest that human activities may be inadvertently contributing to the spread of these cancers to new places and species
According to the researchers, the genetic similarity of the cancer cells found in the clams Venus verrucosa, both in the Atlantic Ocean and in the Mediterranean Sea, suggests that “human navigation activities can having transported cancer from one region to another”, says Bruzos, now at the Francis Crick Institute in London (United Kingdom).
The team now hopes to carry out further studies to determine the age of the tumors in their clam specimens and explore how long the cancer may have spread between these species.
On the other hand, “the genetic study of these contagious cancers is a new point of view to try to understand metastasis . With this new case of contagious cancer, we now have more models to study the genetic causes of cancer transmissibility”, concludes Tubío.
García-Souto, D., Bruzos, A.L., Díaz, S. et al., 2022. “Mitochondrial genome sequencing of marine leukemias reveals cancer contagion between clam species in the Seas of Southern Europe”. eLife .
Rights: Creative Commons.