Bees possess a sense of smell 100 times more sensitive than the human nose. With 170 odor receptors at their disposal, they're able to recognize the presence of faint metabolic gases emitted by cancer cells during the earliest stages of disease.
A handful of scientists are looking into ways that insects might better relay this information, and are keen to incorporate bugs with this unique ability in a clinical setting. Researchers at the University of Georgia, for instance, have invented a handheld device containing parasitic wasps trained to move toward certain odors. They then use computer software that analyzes film of the wasps' movements to determine which patterns indicate that a smell has been positively identified. As I covered late last year, Christina Soares, a British industrial designer, applied an elegant approach to behavioral training, in developing a glass apparatus called Bee's. She made it so that merely introducing gases containing disease biomarkers, like a patient's breath, would cause a colony of bees to swarm into the test chamber.
But perhaps the most promising method for using insects to diagnose tumors comes from a recent experiment carried out by researchers from the University of Konstanz in Germany and the University La Sapienza in Italy, which demonstrated that fruit flies can be genetically modified to glow the moment they come in contact with these volatile molecules.
It doesn’t get more straightforward than that. A fruit fly possesses less than half as many odor-sensing receptors as a bee, but its olfactory system is apparently still sensitive enough to distinguish cancerous cells from healthy ones, according to the team's report. Moreover, the researchers found that the receptor neurons on the flies' antennae were able to differentiate between five types of breast cancer.
For the study, detailed in the journal Nature, the investigators devised a machine that blew the odor emitted from five different strains of lab-grown breast cancer cells, along with healthy in vitro human breast tissue, over an area containing the flies. They then used a microscope to examine the fluorescent patterns that became visible on the flies' antennae as their receptor neurons detected the odors.
Drosophila are considered model organisms for researchers looking to better understand how our own bodies work. The fruit fly's relatively simple base genome can easily be tweaked; scientists selectively turn on and off specific genes and also introduce mutated human genes. In the past, bioengineers have created mutant flies with fluorescent digestive systems to study the mechanisms behind constipation and water retention during pregnancy. They’ve also been used to study the progression of Alzheimer's.
The popular lab insects are inexpensive to breed and possess short life cycles that allow for efficient research. The study's lead author Giovanni Galizia of the University La Sapienza stated in a release that fruit flies may be ideally suited for this important role in medical research, given these traits.
"The high sensitivity of the natural olfactory receptors, paired with the quickness with which we can generate these test results," he says, "might lead to the development of a cheap, fast and highly-efficient pre-screening that can detect cancer cells well before we can discover them with the present diagnostic imaging techniques."