Radiation resistant worms in Chernobyl could be key for cancer research

Worms living near the nuclear disaster zone in Chernobyl have "exceptional" resistance to radiation, potentially providing some valuable insights into cancer in humans.

While the 1986 disaster at the Chernobyl nuclear power plant in northern Ukraine sparked a mass evacuation of the area, many plants and animals have continued to survive in the region.

A recent study found cancer-resistant wolves living in the Chernobyl exclusion zone (CEZ), and now researchers have identified microscopic worms with the same advantages.

Exposure to chronic radiation has failed to damage the genomes of worms living in the area today, researchers from New York University found.

In recent years, researchers have found that some animals living in the exclusion zone — within an 18.6-mile radius of the power plant — are physically and genetically different from their counterparts elsewhere.

This, researchers say, raises questions about the impact of chronic radiation on DNA, which could provide some clues for scientists researching cancer in humans.

“Chernobyl was a tragedy of incomprehensible scale, but we still don't have a great grasp on the effects of the disaster on local populations,” said Sophia Tintori, a postdoctoral associate in the Department of Biology at NYU and the first author of the study.

“Did the sudden environmental shift select for species, or even individuals within a species, that are naturally more resistant to ionizing radiation?”

To find an answer to this, Dr Tintori and her colleagues turned to nematodes, tiny worms with simple genomes and rapid reproduction, which makes them particularly useful for understanding basic biological phenomena.

“These worms live everywhere, and they live quickly, so they go through dozens of generations of evolution while a typical vertebrate is still putting on its shoes,” said Matthew Rockman, a professor of biology at NYU and the study’s senior author.

“I had seen footage of the exclusion zone and was surprised by how lush and overgrown it looked—I'd never thought of it as teeming with life,” added Dr Tintori.

“If I want to find worms that are particularly tolerant to radiation exposure, this is a landscape that might have already selected for that.”

In collaboration with scientists in Ukraine and colleagues in the US - Dr Tintori and Prof Rockman visited the Chernobyl Exclusion Zone in 2019, using Geiger counters to measure local levels of radiation as they gathered samples of worms, soil and other organic material.

They focused their analyses on 15 worms of a species called Oscheius tipulae, which has been used in previous genetic and evolutionary studies.

They sequenced the genomes of the 15 O. tipulae worms from Chernobyl and compared them with the genomes of five O. tipulae from other parts of the world.

Using several different analyses, scientists were surprised to find they could not detect a signature of radiation damage on the worms from Chernobyl.

“This doesn't mean that Chernobyl is safe—it more likely means that nematodes are really resilient animals and can withstand extreme conditions,” noted Dr Tintori.

“We also don’t know how long each of the worms we collected was in the zone, so we can't be sure exactly what level of exposure each worm and its ancestors received over the past four decades.”

Researchers suspected the lack of genetic signature was because the worms living in Chernobyl are unusually effective at protecting or repairing their DNA.

They designed a system to compare how quickly populations of worms grow and used it to measure how sensitive the descendants of each of the 20 genetically distinct worms were to different types of DNA damage.

While the lineages of worms were different from each other in how well they tolerated DNA damage, these differences didn't correspond to the levels of radiation at each collection site.

Their findings suggest that worms from Chernobyl are not necessarily more tolerant of radiation and the radioactive landscape has not forced them to evolve.

The results give researchers clues into how DNA repair can vary from individual to individual, and could lead to a better understanding of natural variation in humans and why some people are more likely than others to suffer the effects of carcinogens.

How different individuals in a species respond to DNA damage is top of mind for cancer researchers seeking to understand why some humans with a genetic predisposition to cancer develop the disease, while others do not.

“Thinking about how individuals respond differently to DNA-damaging agents in the environment is something that will help us have a clear vision of our own risk factors,” added Dr Tintori.

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