'Junk DNA' could spotlight breast and bowel cancer

Cancer Research UK

Cancer Research UK funded scientists have found that a group of rogue genetic messengers, produced by DNA sequences commonly known as ‘junk DNA’, could help diagnose breast and bowel cancer. Their research is published in the journal Genomics.

The researchers, led by Dr Cristina Tufarelli at the University of Nottingham, discovered that seven of these faulty genetic messengers – known as chimeric transcripts - are more common in breast cancer cells. Five were only present in breast cancer cells while two were found in both normal and breast cancer cells.

These rogue messengers are produced by DNA sequences called LINE-1 (L1). Despite being labelled as ‘junk DNA’ it is clear that some of these sequences have important roles in the genome, such as influencing when genes are switched on.

L1s carry a switch that is able to randomly turn on nearby genes. When genes are inappropriately switched on in this way, they make the rogue genetic messengers that can sabotage the normal functioning of cells. To prevent the potentially damaging effects of these rogue elements, normal cells silence L1s with a chemical ‘off switch’.

In cancerous cells this ‘off switch’ is often missing, leading to the production of these rogue genetic messengers.

Lead author Dr Cristina Tufarelli, a lecturer at the University of Nottingham supported by Cancer Research UK, said: “This study has generated new research tools to investigate the role of ‘junk DNA’ in cancer development. The next step is to find out if the switching on of these genes is driving cancer or if they are a result of the cancer. Even if they are innocent bystanders of cancer they could be useful biomarkers helping us to diagnose or monitor the disease.”

The researchers extended their studies to look at two bowel cancer cell lines. Two of the rogue messengers were only found in invasive bowel cancer cell lines suggesting that these sequences could play a role in cancer progression.

Dr Cristina Tufarelli added: “If this ‘junk DNA’ does turn out to play a role in cancer then we could be at the tip of the iceberg in understanding a completely new mechanism behind the disease. If we do find out that they are playing a role then they could be useful targets for new treatments.”

Dr Lesley Walker, Cancer Research UK’s director of cancer information, said: “These really interesting findings are the most comprehensive study of these transcripts that have ever been carried out. We are learning more about the genes involved in cancer but these so-called ‘junk’ regions receive relatively little attention. We are beginning to see that they could play a really important role.”

ENDS

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References

Cruickshanks, H., & Tufarelli, C. (2009). Isolation of cancer-specific chimeric transcripts induced by hypomethylation of the LINE-1 antisense promoter Genomics, 94 (6), 397-406 DOI: 10.1016/j.ygeno.2009.08.013