- Cancer is a leading cause of death worldwide, accounting for nearly
10 milliondeaths in 2020. One way to improve survival rates is to develop better diagnostic methods.
- Early detection is crucial, as patients have a higher chance of recovery if the cancer is found sooner. Currently, many early detection methods are either invasive or expensive, making them unavailable to many people.
- One alternative method being studied involves the use of animals’ sense of smell. Now, scientists have shown that ants can detect the “scent of cancer” from urine, which one day could represent a cheap and effective cancer detection method.
In a new study paper published in Proceedings of the Royal Society B: Biological Sciences scientists report that ants can detect the scent of several types of cancer, which changes the odor of urine.
Animal olfaction refers to the sense of smell in animals. This sensory ability is used by many species, including mammals and insects, to detect and identify scents in their environment for various purposes, such as finding food, detecting predators, and locating mates.
Cancer cells can emit specific chemicals called volatile organic compounds (VOCs), that can be used to identify cancer. Animals, including ants, with their strong sense of smell, can therefore be trained to recognize these VOCs.
Using animals to detect cancer is a promising way to increase early detection rates. Dogs, for example, can be trained to identify cancer by smelling cell samples or body odor and detecting VOCs that are associated with cancer and its altered cell metabolism.
Ants, particularly Formica fusca, show excellent learning skills when it comes to odors that are relevant to their environment.
While ants do not have a sense of smell in the same way in which mammals do, they are able to pick up distinct smells through their antennae, which have an exceptional number of odor receptors.
After just one training session, ants are capable of creating a long-lasting memory that lasts for several days. Additionally, they have strong memory retention, as they can still respond accurately after multiple tests without a reward, even up to nine times.
In the current study, the researchers trained 70 Formica fusca, a relatively common ant species in the Northern Hemisphere, to smell the difference between urine from healthy mice and mice grafted with cancer tumors collected from humans.
After only three training sessions, the ants were able to reliably identify VOCs. These findings suggest that ants have the potential to be used as a cheap and effective way to detect cancer.
This study expands on previous work by the research team, where they demonstrated that ants can detect human cancer cells grown in a laboratory setting.
The researchers used urine samples from mice that had human tumors growing inside them to detect cancer. These mice, called patient-derived xenograft mice, are a better model for detecting cancer compared to cell cultures because the cancer cells are growing inside a live organism with all its complexity.
Additionally, the tumors in these mice are stable over time and can be duplicated, making it possible to test many different treatments and find the best one for the patient whose tumor was used.
They did this by teaching individual ants to recognize a certain smell, the urine of mice, with a reward — a sweet solution. They placed the ant in a circular arena and performed three training sessions. The time it took the ant to find the reward was measured during each training session.
The researchers showed that the ants could learn to recognize a mixture of different smells that are associated with a reward.
After only three training sessions, they were able to tell the difference between mice with tumors and those without by sniffing their urine. They also noted that the bigger the tumor is, the more the mouse’s urine smell changes from normal.
Dr. Baptiste Piqueret, from the Lise Meitner Research Group Social Behaviour, Max Planck Institute for Chemical Ecology in Jena, Germany, one of the study authors, explained the key findings to Medical News Today.
“Last year we found that ants can smell cancer odor using human cell lines. In the new study, we found that ants are able to detect the presence of human tumors in a whole organism, by smelling the urine of the ‘patient’ (we used mice graft with human tumors),” Dr. Piqueret said.
Dr. Piqueret emphasized just why ants could provide a promising cancer detection method. He told us that:
“This proof of concept demonstrates that ants have the potential of being used as efficient and inexpensive bio-detectors of cancer (in [the] future, as we need to validate the ants abilities using human samples). Furthermore, they are fast to learn, easy, and cheap to maintain.”
James Dobbyn, National Health Service senior research nurse and acute oncology clinical nurse specialist, who was not involved in this research, noted that “whilst patients may find it hard to comprehend this technology, the results of this research, if confirmed, could have far-reaching benefits for our patient populations.”
Dobbyn continued: “For example, in ovarian cancer which accounts for 70% of all gynecological cancers, due to non-specific symptoms, 75% of these women are diagnosed at stages III and IV. This means that their cancers are much harder to treat.”
“Clearly, earlier detection leads to better patient outcomes and novel screening strategies like this are welcomed if they are a reliable and practical solutions in the clinical setting.” Still, “[m]ore research is needed,” he pointed out.