Ants that can ‘smell’ cancer

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Thanks to their highly sensitive olfactory system, ants could one day be used to help detect cancer in humans, suggests a new study.

So far, scientists have discovered that ants are capable of detecting the disease in mice.

“Ants can be trained in ten minutes to smell cancer in the urine of mice,” Baptiste Piqueret, lead author of the study, told the BBC.

Piqueret, who started his research in the area in 2017, managed to train ants to distinguish between healthy cells and cancer cells grown in the laboratory.

But now, his team has gone a step further: the ants have this time detected human tumors in mice.

TRAINING ANTS TO DETECT MALIGNANT ODOR

Piqueret and his team used a technique called xenograft — which consists of transplanting human breast cancer into mice and allowing it to grow.

Next, they collected urine samples from both healthy mice and those with cancer.

“During training, we put the ants in a circular arena and placed food as a reward next to the urine of the cancer mice,” he says.

As the ants find the reward, they associate the scent of the cancer cells with it and learn to recognize it.

“Cells are like factories, they need nutrients to live and they produce waste. Cancer cells produce waste that can be detected in the odor”, says Piqueret.

More specifically, as the study explains, cancer cells have specific volatile organic compounds that can be detected in urine or breath.

During the training process, the ants lingered around the cancerous urine samples longer, even after the scientists removed the rewards.

CAN ANTS BE USED TO DETECT CANCER IN HUMANS?

Not yet, says Piqueret.

“To go further, we would have to start testing human urine,” he adds, but that would be more complicated than testing mouse urine.

Training ants to detect carcinogenic odor in humans would include many variables — such as age, sex and diet — but also a specific odor that every human has.

“Humans don’t have the same odors, they differ from person to person, and we don’t know if ants can concentrate only on cancer cells,” explains Piqueret.

But he is committed to further research, as he believes that ants can be extremely effective and low-cost detectors – and do not require a lot of time to train.

“One of the advantages could be the fact that ants live in colonies and share information with each other”, he says.

Piqueret suspects that if 10% of the ants in a colony are trained to detect cancer, they can spread the knowledge to the rest.

“Perhaps the information would spread, and we wouldn’t have to waste time training the entire colony”, he observes.

This theory has already proven to work with bees — but, he said, more research with ants would be needed.

WHAT OTHER ANIMALS CAN HELP DETECT CANCER?

For ten years, Debajit Saha, from Michigan State University, in the USA, has been studying locusts and their ability to help detect cancerous cells.

His team found that grasshoppers can “smell” the difference between cancerous and healthy cells.

But they’re not trying to train locusts — instead, they’re trying to exploit their brains.

“We can go directly into the brain and use existing neuroscience knowledge to create a model from the neural signals,” Saha tells the BBC.

They hope that the knowledge gained from studying grasshopper brains will provide a basis for building a device that uses insect sensory neurons to detect cancer using just a patient’s breath.

“I like the whole idea of ​​using biological organisms and thinking about how to use them to detect disease,” says Saha.

But it’s not just insects that can help.

In the UK, a charity called Medical Detection Dogs has been working on developing an “electronic nose” that can sniff out prostate cancer.

“Our work started by investigating whether dogs could find bladder cancer. It looked at the effectiveness of dogs finding it from samples collected from the urine of cancer patients,” says Sophie Aziz, head of research and business development at the organization, to BBC.

The institution trained six dogs of different breeds in 2004 and found that the diagnostic accuracy was three times greater than the rate expected by chance.

Later studies confirmed that dogs are able to sniff out bladder cancer with an accuracy of around 90%.

Another study showed that dogs can also smell ovarian cancer from patients’ blood samples. Trained dogs were able to detect it in 99% of cases.

Then came the research to develop an “electronic nose”, but it has been challenging because of the nuances of the odor.

“Particularly when it comes to disease, odors can be different depending on the person’s microbiome and their immune response to the disease,” explains Aziz.

But she believes that the new research with insects can be complementary to other studies of cancer detection.

“The more we can learn about the animal kingdom, the better. The more research that comes from groups like ours, or from scientists who analyze how ants can detect cancer, the better. Everything contributes to building a broader view”, he evaluates Aziz.

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