Ants could detect human breast tumours, according to a small study in mice. The insects may one day provide an easier and cheaper way to non-invasively identify tumours compared with sniffer dogs.
Cancer cells are known to produce molecules called volatile organic compounds, which give them specific odours. As a result, some dogs can use their highly sensitive noses to sniff out cancer, but training them can be expensive and time-consuming.
Now, at Sorbonne Paris Nord University in France and his colleagues have shown that a species of ant, Formica fusca, can be trained to smell the difference between the urine of mice that have implanted human tumours and those without tumours.
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The researchers implanted human breast tumour cells derived from one person into six mice. They allowed the tumours to grow in the animals for seven weeks before collecting urine from the mice. The team also collected urine from six mice that underwent the same surgical procedure, but didn’t have tumour cells implanted.
The researchers then trained 70 ants to either identify urine produced by the mice with implanted cancer cells or to identify urine produced by those without tumours, according to the urine’s smell. To do this, the insects were placed in the centre of a petri dish. One end of the dish held urine from the mice with breast tumours and the opposite end had urine from the mice with no tumours, with the ants receiving a sugar-water reward when they correctly moved towards the urine sample they were being trained to detect.
After just two training sessions, and within 20 seconds of being placed in the centre of the dish, the ants moved towards the urine samples they had been trained to receive a sugar-water reward from.
To test the ants’ memories, the researchers then repeated the experiment without any sugar water in the dish. The insects were placed in the dish for 2 minutes, during which time they spent about 30 seconds in the area with the urine sample they had been trained to recognise.
This is compared with about 25 seconds in the area containing the other urine sample. Although a 5-second difference seems small, the researchers found it to be statistically meaningful, rather than down to chance. This suggests the ants remembered the difference between the smell of urine from mice with and without tumours.
Further work is needed to establish whether ants can detect the presence of a wider range of human tumours implanted in mice or if they can detect tumours in human urine.
Reference: bioRxiv DOI:
