15 February 2016
ByAppeared in BioNews 839
A blood test to diagnose common types of cancer is in development after researchers found that five forms of the disease share a telltale chemical signature.
Researchers at the US National Human Genome Research Institute found that tumours in colon, lung, breast, stomach and endometrium share a change in a gene called ZNF154. Knowing that DNA from tumours can circulate in the bloodstream, the team proposes it would be possible to detect this change and diagnose cancer from a standard blood test.
'We have laid the groundwork for developing a diagnostic test, which offers the hope of catching cancer earlier and dramatically improving the survival rate of people with many types of cancer,' said Dr Laura Elnitski, whose research group led the study, published in The Journal of Molecular Diagnostics.
In 2013, the research group analysed cancerous tumours from 13 different organs, and found that DNA methylation was commonly increased at ZNF154 in all tumour types. DNA methylation acts like a chemical 'dimmer switch' on genes: an increase in methylation causes a decrease in gene activity.
The current study focused on the possibility of using the enhanced methylation as a reliable indicator of cancer. The team compared 184 samples from five different tumour types with 34 normal, non-cancerous tissue samples.
'Finding a distinctive methylation-based signature is like looking for a spruce tree in a pine forest,' said Dr Elnitski. 'It's a technical challenge to identify, but we found an elevated methylation signature around the gene known as ZNF154 that is unique to tumours.'
Importantly, they found that this genetic change was consistent across the five different types of cancer, suggesting that it could be used as a universal cancer marker. The study also showed that the enhanced methylation was detectable even at very low concentrations in the blood, meaning that a blood test could be used to identify cancer from early-stage tumours.
Currently, diagnostic tools for cancer are reliant on physical examination, internal imaging and biopsies. Where blood tests are used, they are specific to a certain cancer type and require prior knowledge of suspected cancer.
Using a broader and more sensitive approach, as is hoped for the new blood test, would not only be less invasive, but also more likely to detect cancer at an earlier stage, when treatment is more effective.
The researchers are now focusing on developing the blood test as a diagnostic tool. They will need to confirm whether it outperforms existing methods of screening and diagnosis, notes NHS Choices. Characterising the rate at which it indicates cancer is present when the disease is not there – or misses cancer when it is present – will also be highly important.
'Their method of detecting this is very sensitive,' Professor Samuel Janes, honorary medical adviser to the British Lung Foundation, told The Telegraph. He added: 'We will have to wait and see if this actually works.'