These Ants Were Trained to Sniff Out Cancer

In just ten minutes, an ant could learn to identify urine from mice with cancerous tumors, a new study finds

A formica fusca ant on a leaf
Ants don't have noses, but they detect scents using antennae atop their heads. Sanja565658 via Wikimedia Commons under CC BY-SA 3.0

Scientists want to train insects to test humans for cancer.

In a new study, published Wednesday in Proceedings of the Royal Society B, ants could differentiate between the smell of urine from healthy mice and from mice with cancerous tumors.

The research serves as a proof of concept demonstrating that ants could someday be used as a fast, inexpensive and noninvasive tool for detecting cancer, the authors write.

“This is an exciting direction,” Debajit Saha, a biomedical engineer at Michigan State University who studies locusts’ ability to detect cancer but was not involved in the new research, tells Scientific American’s Jude Coleman. Using insects is a “new and very powerful approach to disease detection.”

“The results are very promising,” study co-author Baptiste Piqueret, an ethologist at the Max Planck Institute for Chemical Ecology in Germany, tells the Washington Post’s Dino Grandoni. But “it’s important to know that we are far from using them as a daily way to detect cancer.”

Finding cancer early can increase people’s chances of survival, but early detection methods can be both invasive and expensive. Instead, scientists have explored harnessing animals’ olfactory systems to screen people for the disease.

Tumor cells release volatile organic compounds (VOCs) that some animals can sniff out. In previous studies, dogs have detected VOCs from tumors in cell samples and body odors. And researchers showed one species of roundworm was attracted to some VOCs from cancer.

While ants don’t have noses, they have a highly developed sense of smell. Antennae atop their heads detect and release odors to find food, attack prey and protect their young, writes the Post. In a 2022 study, Piqueret and others showed that Formica fusca ants could smell the difference between lab-grown cancer cells and healthy cells.

In the new study, the researchers transplanted particularly aggressive breast cancer tumors from humans onto mice. They then exposed 35 Formica fusca ants to the scent of urine from the cancerous mice and trained them to associate it with a sugary reward. Later, when presented with urine from both sick and healthy mice, the ants spent 20 percent more time around the urine from the sick mice, without the sugar present. This suggests that the ants could distinguish between the two scents and went poking around the sick-mouse pee in hopes of finding sugar.

“The study was well conceived and conducted,” Federica Pirrone, a researcher at the University of Milan in Spain who has studied dogs’ olfaction but was not involved with the new paper, tells the Post.

Cancer-sniffing ants might even provide an advantage over other animals, the authors write. Surprisingly, the ants were relatively easy to train—it only took three trials totaling about ten minutes to get an ant to connect the smell of cancer with the sugary reward.

“That’s something we were not expecting, to see it that fast,” Piqueret tells Scientific American.

But more work needs to be done to show ants can be used with human patients. The mice used in the study were pretty similar—for example, they were from the same lineage and fed the same diet. Human patients would be less homogenous, which could influence their body odors and make it harder for ants to sniff out cancer.

“The diet, sex and age of a patient can impact the odor of the urine,” Piqueret tells Newsweek’s Pandora Dewan.

Future studies should also investigate whether ants trained to detect a single type of cancer can then generalize that ability to detect other kinds of cancer, the authors write.