Are Ants the Future of Cancer Diagnosis?

Cancer diagnosis is often an anxious, invasive, time-consuming, and costly process. More than 230 thousand people in Türkiye and 20 million worldwide undergo this process and receive a cancer diagnosis each year. It involves many biopsy techniques and highly sensitive microscopes for visualizing cancer cells.

Imagine all these procedures being as easy as breathing.

We know some animals – dogs or mice, for example – have highly sensitive noses that can reveal disease by smell. Inspired by these studies, French scientists decided to explore whether ants could achieve this with their known super sense of smell.

Study leader Baptiste Piqueret, a researcher at Sorbone Paris Nord University, says, “Using smell to detect disease is not a new idea”. “Knowing how well ants can learn and how they use their sense of smell, we tested their ability to learn and detect diseases.”

Although still far from real-life clinical use, this could one day lead to a cheaper, more accessible, if somewhat unusual, alternative for detecting cancer. What do you think new diagnostic methods might look like?

Pavlov’s Ants

Cancer cell metabolism produces volatile organic compounds (UOBs), organic chemicals that give off odors and can serve as diagnostic biomarkers.

To train ants to target UOBs, the researchers placed breast cancer cells and healthy cells in Petri dishes – but gave sugar to the cancer cells. Piqueret says, “We associated the smell of cancer with a reward”.

This is a technique scientists call classical or Pavlovian conditioning. A neutral stimulus (cancer odor) is associated with a second stimulus (food) eliciting a behavior. After several repetitions, ants learn that the first predicts the second and seek the odor expecting food. After training, researchers presented the learned odor and a new one – this time without a reward. The ants indeed spent more time exploring the learned odor than the new one.

Piqueret said: “If you are hungry and smell fresh bread, you go to the nearest bakery and learn that the smell of fresh bread means food. That is the same mechanism the ants use.”

The researchers note that dogs can detect UOBs in the same way, but conditioning takes months and hundreds of attempts. Only 3 training trials appear sufficient for F. fusca ants to learn quickly.

Below is a graphical abstract of the study:

Why Ants?

Ants primarily communicate through smell. This sophisticated language also makes them highly sensitive to odors and smelling.

Corrie Moreau, a biologist and entomologist (insect scientist) at Cornell University, says, "Since ants are already well adapted to detecting different chemicals, this makes them ideal for odor recognition". In their tiny ant world, these creatures produce chemicals called “pheromones” to communicate information to another member of their nest.

Moreau says: "There are pheromones signaling an intruder, pheromone trails showing an ant which path to take to food, and colony-level odors indicating that another ant belongs to the same colony."

Look more closely, however, and you will not see a nose on an ant. They “smell” with their antennae. Moreau continues: "These specialized structures are covered with receptors sensitive enough to distinguish even small chemical differences."

Scientists know of more than 14,000 ant species, all communicating with their antennae. Some, however, are better than others at detecting compounds, such as those scientists are considering for disease detection.

Diagnostic Ants: Realistic or Just a Curiosity?

Moreau says it is too early to tell whether this new research can lead to a real tool for cancer diagnosis.

Anna Wanda Komorowski, a medical oncologist-hematologist at Northwell Health in New York, finds the ant study interesting and says she is impressed by how the researchers detected the ants. However, further research is needed to establish how long ants remember their training and how long they can be kept in a laboratory for testing.

If the method works, an appealing feature is its lower cost than standard laboratory procedures for detecting cancer cells. In low-income research settings, it might therefore replace methods that can be hard to access, such as detecting cancer cells through staining.

Komorowski highlights another obstacle: the cells to which ants would be exposed would probably differ from those used in the study. The study exposed ants to live cell cultures, but biopsies are usually placed in formaldehyde, which has a very strong smell. A different laboratory protocol would therefore be needed for cancer detection, which could be difficult.

Although ants cost less than staining methods, dyes, and formaldehyde, people might need to be hired to train them, creating a new line of work – the human factor and associated costs must also be remembered. Komorowski says, "Much more research is needed to understand the cost and how feasible and reproducible this would be”. Another question is whether ants would detect cancer only in the laboratory or whether direct patient interaction could lead to a faster diagnosis.

Moreau, an ant specialist, concludes: "The human body gives off many other odors, so the question is whether ants can ignore them all and focus only on the target. These results are promising, however. There is also the question of whether a patient would want trained ants roaming all over their body looking for potential cancer cells."