Chernobyl Tissue Bank Provides a Unique Resource to Researchers
Twelve years after the 1986 Chernobyl nuclear reactor disaster, a tissue bank was established to coordinate access to high-quality tissue samples for research purposes and to integrate data on radiation-related thyroid cancer. Today, the Chernobyl Tissue Bank (CTB) serves as a unique resource for research on the biology of thyroid cancer.
Since 1998, the CTB has been collecting tissue and blood samples from patients who were exposed to radioactive iodine, or radioiodine, from Chernobyl fallout and who later developed thyroid tumors. The samples are a limited resource. To extend the research that can be conducted with a single specimen, approved researchers receive nucleic acid extracted from the thyroid tissue, instead of the tissue itself. Paraffin-embedded sections of tissue from loco-regional metastases and tissue microarrays are also available.
“The CTB represents a good model for global collaboration to advance the understanding of the biology of a particular cancer,” said Dr. Rihab Yassin, NCI’s representative to the CTB international steering committee, which is responsible for the strategic direction of the project. She also serves as the NCI program official for the grant that provides support for CTB research.
A Global Research Effort
The original idea behind the CTB was to collect tissue samples from people with Chernobyl-associated thyroid tumors and to make those samples available to researchers around the globe, explained Dr. Geraldine Thomas, director of the CTB and professor of Molecular Pathology at Imperial College, London. That vision is now a reality. A new online portal, launched April 26 to coincide with the 25th anniversary of the accident, makes it easier to search for samples and corresponding data.
The CTB is the first international effort to house specimens from tumors that are caused by a known environmental source to further global research collaboration. The tissue banks are located in two of the countries greatly affected by the disaster—Ukraine and Russia—and the database is maintained at the Coordinating Centre at Imperial College, London. The CTB is supported financially by the European Commission, NCI, and the Sasakawa Memorial Health Foundation of Japan.
To date, the CTB contains thousands of samples from 2,840 patients, who fall into one of three categories: individuals who were 19 years old or younger at the time of the accident; those who were born between April 27 and December 31, 1986, when they were likely exposed to radioiodine in utero; and those born in the affected region after January 1, 1987, when the radioisotope iodine-131 (I-131) had already dissipated in the environment.
Decades Later, Better Experiments
Since its inception, the CTB has provided material for research projects in Japan, Europe, and the United States. Investigators must submit an application detailing their research project in order to gain access to the samples. The application is subject to review and scoring by an international External Review Panel (ERP) to ensure the scientific quality of these research projects.
One of those studies, the NCI-sponsored Ukraine-American Cohort study, is examining the relationship between radiation dose and the molecular biology of the tumors. The European Commission sponsored a study to identify pathways that are important in radiation-associated thyroid cancer.
“We’ve now reached a place,” Dr. Thomas said, “that will add much more valuable data to what we know.” The population that was exposed to the radioiodine is just now reaching the age (25 to 44) that is associated with an increase in incidence of sporadic thyroid cancer. “We don’t really know what’s going to happen with these individuals,” she said. “Have we already seen a peak in radiation-induced thyroid cancer? Or will there be even more cases as the exposed population approaches the usual peak for incidence of this disease?”
Additionally, researchers are observing people from nearby geographic areas who were not exposed to radioiodine and who have now reached the age at which thyroid cancer may develop spontaneously. “We had to wait 20 years to do the proper experiment,” Dr. Thomas said, “which is taking age-matched cohorts and comparing sporadic thyroid cancer to radiation-induced thyroid cancer.”
Several reports have suggested that there may be small differences, such as chromosomal amplification in a proportion of radiation-associated cancers that aren’t seen in the non-radiation-associated cancers. However, these studies need to be validated, Dr. Thomas stressed, which is why the CTB’s work is important. Other findings from research projects using CTB tissue samples suggest that thyroid cancers that arise in younger patients are molecularly different from adult-onset thyroid cancer.
From Research to Possible Treatments
The next phase for the CTB is to make bioinformatics tools available to researchers so that they can continue to analyze data, Dr. Thomas said. She also hopes that the data collected from the CTB will eventually help advance patient care.
“We’d like to be able to use the primary tumors to tell which tumors will recur, so that we can treat those patients differently,” she said. “Nobody has ever systematically collected this number of tumors for research purposes, so the CTB will help answer a lot of questions.”
And the incidence of sporadic thyroid cancer appears to be increasing in the United States, Dr. Yassin noted, although the reasons for this increase are being debated. “The CTB samples are important to help understand these cancers as well.”
Dr. Thomas agreed, adding that the incidence rate of thyroid cancer is climbing globally. She hopes that what is learned from the Chernobyl-related thyroid cancers will boost general knowledge of the disease. “The most important thing is, can we do something to help patients in the future?” she asked.
The research done with CTB material could also be relevant to the recent events in Japan, said Dr. Thomas. “My message has been, don’t panic. We’ve done research on Chernobyl, and we know it’s children and pregnant women who need to be most careful. The Japanese government communicated that message to the Japanese population very effectively.”