News Release

Genomic analysis reveals ancient cancer lineages in clams

Study findings reshape understanding of cancer evolution

Peer-Reviewed Publication

Pacific Northwest Research Institute

Michael Metzger, Ph.D., Assistant Investigator, Pacific Northwest Research  Institute


Michael Metzger, Ph.D., Assistant Investigator, Pacific Northwest Research  Institute

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Credit: Pacific Northwest Research Institute

Seattle, WA – October 2, 2023 – In a new study published in the journal Nature CancerMichael Metzger, Ph.D., Assistant Investigator at Pacific Northwest Research Institute (PNRI), and a global team of co-investigators have conducted a comprehensive analysis of the genomic changes associated with a unique cancer in clams. The cancer is “transmissible” in that the cancer cells themselves jump from one clam to another through the environment. The study traced the evolution of the cancer cells over the last 200 years and revealed widespread genomic mutations and instability, which may explain how they have survived for so long.  These results highlight the clam's potential as a model for studying both cancer evolution and the development of resilience to cancer. 

Clams and other marine bivalves, such as cockles and mussels, have been found to have leukemia-like transmissible cancers, which can lead to deadly outbreaks that can lead to severe population losses. In recent years, Dr. Michael Metzger and other scientists have studied transmissible cancers in soft-shell clams that were first reported in the 1970s. This study, conducted by researchers at PNRI, the University of Washington, the University of Maine at MachiasColumbia UniversityTexas A&M University, the National Human Genome Research Institute, and Universidad Andrés Bellos in Santiago, Chile, breaks new ground by examining the genomic mutations that have occurred during the evolution of these transmissible cancer lineages within these marine organisms.

The study is published alongside an independent study of a transmissible cancer in cockles in Europe conducted by Jose Tubio, Ph.D.Adrian Baez-Ortega, Ph.D., and others at the Universidade de Santiago de Compostela in Spain. Together, these two studies enable scientists to learn what is different about individual transmissible cancers and what mechanisms they have in common, providing new information critical to understanding how cancer evolves.

Dr. Michael Metzger commented on the significance of these findings, stating, "This work offers us a window into the evolution of these amazingly long-lived cancers and changes our understanding of how cancer cells can survive to continue to infect their hosts despite massive genomic rearrangement and mutation.”

The genomic analysis of cancer in clams advances current knowledge of cancer biology and underscores the importance of studying contagious cancers in their natural settings. 

Dr. Metzger added, “By understanding how these cancers evolve, and how the clams themselves evolve in response to these infectious cancers, we hope to gain insights that could help us develop novel strategies for blocking cancer in humans and other species. It’s a natural experiment that provides a unique opportunity to give us insight into cancer that we could not get anywhere else."


About PNRI:
Pacific Northwest Research Institute (PNRI) is a nonprofit biomedical research institute, where scientists are using innovative approaches in genetics and genomics to tackle some of the most difficult problems in science and medicine. The institute was founded 67 years ago in Seattle, Washington, as a place where scientists were free to pursue discoveries that promised the highest chance of improving human health. The goal was at the beginning, and remains today, to conduct foundational science leading to impactful medical innovations. To learn more, visit

Media contact:
Louise Maxwell

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