September 23, 2014 | by Nicole White
The environment plays a role in causing cancer – this much we know. But scientists are still trying to understand what that role is, what environmental factors are in play and how precisely those factors are linked to cancer.
Now City of Hope researchers have unlocked a clue as to how one carcinogen triggers cancer, and they hope this discovery will shed light on how other environmental factors may cause cancer. The study, published online recently in the Proceedings of the National Academy of Sciences, focused on one carcinogen in particular, nickel.
In the United States, fossil fuel combustion is the leading culprit for spewing nickel into the air we breathe. In other countries, heavy metal factories are also a common cause. Breathing in nickel increases the risk of nasal cancer and of lung cancer, the leading cancer killer of men and women in the U.S.
“Nickel has been proven to be a carcinogen, but unlike most carcinogens, it doesn’t change the DNA at all,” said Dustin Schones, Ph.D., assistant professor of cancer biology at City of Hope and a lead author of the paper.
So if the answer wasn’t in the body’s genome, perhaps it was in the epigenome. The genome consists of the genetic material of an organism – a kind of “blueprint.” Layered over this genome is the epigenome, the ways in which genes are chemically modified that define how the “blueprint” is implemented and expressed.
The genome is organized into active or repressive domains – sets of genes that are switched “on,” and others that are not expressed. Schones and his colleagues found that nickel disrupts these domains, and silences – or switches “off” – parts of the genome that should be active.
This finding could help explain how environmental pollutants cause cancer – and could have implications beyond lung and nasal cancers and cancers linked to nickel. Schones and his colleagues continue to map the epigenome, and plan to continue studying the mechanism nickel triggers to silence genes that should not be silenced.
In time, they hope to understand how our environment can cause cancer – and what steps we can take to avert those risks.
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