Evolutionary origins of 'junk DNA' may provide new clues to cancer

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In cancer research, one person's junk is increasingly becoming another person's treasure. Scientists have uncovered new evidence showing how recently evolved "junk DNA" genetic elements can become integrated into ancient cellular pathways that regulate cancer. These findings may provide fresh insights into how evolutionary forces shape disease and reveal potential new targets for cancer research.

In a study published in Science Advances, researchers from Arizona State University and an international team led by Tianjin Medical University have examined the evolutionary history of junk DNA molecules that were first identified a generation ago through the Human Genome Project.

The phrase "junk DNA" often refers to DNA elements that do not produce proteins and may not contribute to an organism's performance. Numerous classes of such elements make up much of the human genome. Scientists had questioned why they were there. But further research showed this was a misnomer when the elements were found to play an important role in helping regulate how genes function, including through emerging insights into how they may be associated with diseases like cancer.

Now referred to as long noncoding RNAs (lncRNAs), many are unique to primates and humans, and scientists have increasingly recognized them as important players in cancer.

By performing a comparative genomic study, the researchers found that many cancer-associated lncRNAs first emerged as smaller, nonfunctional RNA fragments (microRNA elements) through increased transcription. These gradually expanded in length to become lncRNAs by incorporating additional genetic material and eventually became integrated into deeply conserved, vital cellular pathways that evolved hundreds of millions of years ago.

"Our findings suggest that cancer-associated long noncoding RNAs are not simply recent evolutionary additions," said Michael Lynch, professor in the Biodesign Center for Mechanisms of Evolution at Arizona State University and co-author of the study. "Instead, they can gradually become integrated into regulatory systems that have existed for hundreds of millions of years, illustrating how evolution continually reshapes the architecture of cellular networks in ways that become relevant to diseases like cancer."

Using genomic sequence analyses of 18,000 lncRNAs across 17 animal species, the researchers reconstructed how lncRNAs first