Cancer diagnosis is frightening, invasive, time-consuming, and expensive. And more than 1.6 million people get that cancer diagnosis every year in the United States. That’s a lot of biopsies and a lot of looking at cells under highly sensitive microscopes.
But imagine if detecting cancer in those samples was as simple as taking a whiff.
We know some animals – like dogs and mice – have very sensitive noses that can sniff out disease. Inspired by those studies, French scientists decided to explore whether ants – known for their olfactory prowess – could do the same.
“Using olfaction to detect diseases is not a novel idea,” says Baptiste Piqueret, PhD, a researcher at Sorbonne Paris Nord University and lead author of the study. “Knowing how well ants can learn and how they use olfaction, we tested the abilities of ants to learn and detect diseases.”
While this is still far away from real-life clinical use, it could one day lead to a cheaper, more accessible (if not a little weird) alternative for detecting cancer. What would this new diagnostic method look like?
Pavlov’s ant
Cancer cell metabolism produces volatile organic compounds (VOCs) – organic chemicals that smell and can serve as biomarkers for diagnosis.
To train the ants to target VOCs, the researchers placed breast cancer cells and healthy cells in a petri dish – but the cancer cells included a sugary treat. “We associated a reward to the smell of cancer,” Dr. Piqueret says.
It’s a technique scientists call classical, or Pavlovian, conditioning. A neutral stimulus (cancer smell) is associated with a second stimulus (food) that elicits a behavior. After doing this a few times, the ant learns that the first stimulus predicts the second, and it will seek out the odor hoping to find that food.
Once the training was complete, the researchers presented the ant with the learned odor and a novel one – this time without a reward. Sure enough, the ants spent more time investigating the learned odor than the novel one.
“If you are hungry and you smell the odor of fresh bread, you will enter the closest bakery,” says Dr. Piqueret. “This is the same mechanism the ants are using, as you learned that fresh bread odor equals food.”
Dogs can detect VOCs via the same technique but take months and hundreds of trials to condition, the researchers note. F. fusca ants learn fast, requiring only three training trials.
Why ants?
Ants communicate primarily through olfaction or scent, and this sophisticated “language” makes them very sensitive to odors.
“Since ants are already well-attuned to detecting different chemicals, this makes them ideal for scent recognition,” says Corrie Moreau, PhD, an evolutionary biologist and entomologist at Cornell University, Ithaca, N.Y.
In their tiny ant worlds, the little creatures use chemicals, called pheromones, to convey information to other members of their nest.
“There are alarm pheromones to signal an intruder, trail pheromones so an ant knows which way to walk to a food source, and colony-level odors that signal another ant is a member of the same colony,” Dr. Moreau says.
But on closer inspection, you won’t see a nose on an ant. They “smell” with their antennas.
“These specialized structures are covered with highly sensitive receptors to be able to discern even small chemical differences,” Dr. Moreau says.
There are over 14,000 species of ants and as far as scientists like Dr. Moreau know, all of them use chemical communication, though some are better than others at detecting compounds, such as those scientists are interested in using to detect disease.