Junk DNA and breast cancer prevention

Researchers have discovered that supposed ‘junk’ DNA — that is, DNA which does not contain genes that code for proteins — plays a role in suppressing breast cancer. The breakthrough marks an important milestone since the sequencing of the human genome in 2000, which found that only 2% of our DNA contains protein codes.

It has recently become apparent that a lot of non-coding DNA is transcribed into non-coding RNA. However, there is still a debate as to whether non-coding RNA serves any function in the cell. Now, scientists from the US and UK have identified a piece of non-coding RNA called GNG12-AS1 that stops cells turning cancerous.

“The number of cells in our body are balanced by the level at which cells replicate and replace the ones that die,” said Dr Adele Murrell, from the University of Bath. “Sometimes the switches that control this growth get stuck in the ‘on’ position, which can lead to cancer.

“As the tumour grows and the cancer cells get crowded, they start to break away from the tumour, change shape and are able to burrow through tissues to the bloodstream where they migrate to other parts of the body, which is how the cancer spreads. This process is called metastasis and requires a whole network of genes to regulate the transformation of cell shape and mobilisation.”

Dr Lovorka Stojic, from Cancer Research UK Cambridge Institute, found that GNG12-AS1 prevents the growth switch getting stuck and suppresses metastasis. She found that this non-coding RNA fragment maintains healthy cells through two mechanisms: by regulating the levels of DIRAS3, a neighbouring gene that is involved in cell replication; and by suppressing a network of genes that prepare cells to change their shape and prepare for metastasis.

So why does cancer still occur if this non-coding RNA is there to protect us? It turns out that GNG12-AS1 is located in a genomic region that often gets damaged in breast cancer patients. This means its control is removed, enabling cancer cells to spread.

The team anticipates their findings, published in the journal Nature Communications, could be used to understand how other non-coding RNAs function and to develop potential gene therapies to treat cancer.