35 Years Later, Studies Reveal a Silver Lining From Chernobyl



Cancers cause mutations in human DNA. Some lines of the genetic code have been removed or mixed and that change allows cells to multiply and grow abnormally. Sometimes DNA genetic changes-people can inherit them from their parents-but sometimes it’s caused by environmental factors. Understanding the DNA of a tumor can help develop prescribed gene therapies to combat it.

For many years, epidemiological studies showed that thyroid cancer particularly common in people exposed to radioactive iodine, especially in people exposed when they were young. In sufficiently high doses, radioactive iodine kills thyroid cells and can be used as a treatment for thyroid cancer and other thyroid conditions. But the radiation from Chernobyl is not enough to kill the cells. However, according to Morton, a month of exposure to a lower dose causes changes in the cells that result in tumors.

In his paper, Morton and his colleagues took a closer look at tumors from people living near Chernobyl, studying the DNA of more than 350 people diagnosed with thyroid cancer after exposed to radiation while still young. They make a comprehensive molecular picture of these tumors. Finally, to see how they differed from thyroid cancers caused by other factors, the researchers compared these tumors against tissue from 81 people born near Chernobyl after 1986 and thyroid cancer developed but was never exposed to radiation. They also compared tumors with data from the Cancer Genome Atlas, which identifies the genomes of thousands of cancers.

They found that cancer cases caused by radioactive iodine exposure after post-immersion altered genes by destroying the twin strands of DNA and breaking them down. In contrast, thyroid cancers in the Cancer Genome Atlas and the control group of 81 undisclosed individuals from the area were more likely to cause mutations with a single point, where only one pair of base DNA is modified.

Following the disaster, scientists monitored several communities near Chernobyl, as well as workers tasked with cleaning and installing the radioactive reactor in a steel and concrete sarcophagus. The researchers also conducted several interviews with residents about their indirect disclosure. For example, radioactive isotopes from the reactor fall into nearby fields and are eaten by grazing cows, transmitting the radiation to their milk and then to people who drink it. That is why information about dairy consumption offers clues about how much radiation a person is exposed to. Physicists and epidemiologists are working together to break down all direct and indirect resistance to a reconstruction of the radiation doses received by people who provide tissue samples. “It’s a unique situation where we know a lot about exposure,” Chanock said. “Most of the many studies of the genome scene have no information on where and what humans are exposed to.”

This gives researchers a chance to take a closer look at how this cancer process works. They discovered that the more radiation a person was exposed to, and the younger they were at the time of exposure, the more double -strand DNA breaks they wanted.

Finally, the team looked at cancer drivers, the specific genes with mutations responsible for tumor growth. They found that the molecular properties of radiation-induced cancers were not all that different from those observed in randomly-occurring thyroid cancers. This is the only reason-double-strand DNA breaks-that is different. “That really gives us an understanding of how radiation causes cancer,” Morton said.

There are no special biomarkers that indicate that these cells are altered by radiation, where scientists say the result of radiation occurs early in the carcinogenic process and that the biomarkers-if any-are lost or washed away as they grow the cancer. That molecular similarity indicates that these cases do not require a novel treatment. “These cancers only look, in the end, like typical thyroid cancers, so there are no specific implications for taking a different approach to treatment,” he said.


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