Gila monster spit inspired new way to detect rare pancreatic tumors

Gila monsters are strange lizards, both physically and chemically. Most people can at least recognize the 5-foot-long lizard due to its striking bumpy, pink and black scales, stocky body, and trademark stubby tail. These are not their only unique characteristics – they are only one of two known lizard species in the world capable of producing venom. Although receiving a bite filled with neurotoxic venom is rarely fatal, it is not pleasant and can cause considerable pain, edema, nausea, and vomiting. But inside the Gila monster’s saliva is also a substance that now shows great promise in helping detect extremely hard-to-find pancreatic tumors.

On rare occasions, the beta cells responsible for producing insulin in the pancreas can malfunction and form small tumors known as insulinomas. Although comparatively benign, these growths can still reduce blood sugar levels due to the overproduction of insulin. This issue is particularly problematic for people with diabetes, as it can result in low energy and even fainting. Furthermore, tumors are usually smaller than 2.5 cm in size, making them difficult to locate and diagnose. Now, however, a new variant of the PET scan appears to accurately assess insulinomas, thanks in large part to the chemical complexities of Gila monster saliva.

Before the lizard-inspired solution, identifying patients with insulinoma was extremely difficult for medical teams. In many cases, it takes a long time to confirm its existence.

“It’s a very challenging disease,” says Marti Boss, first author of a new study published in The Journal of Nuclear Medicinesaid in a statement. “We can do blood tests, but they cannot confirm whether the cause is a tumor or where it is located. Various tests such as computed tomography, magnetic resonance imaging and PET are available, but they do not always show insulinomas.

“In the past, surgeons would start cutting portions of the pancreas until they found the tumor. If it were in the end, the entire pancreas would disappear,” added Martin Gotthardt, professor of nuclear medicine and co-author of the study. “You can live without a pancreas, but you would face severe diabetes and have to constantly control your blood sugar. Therefore, better digitalization was urgently needed.”

Gotthardt and Boss knew of the promising uses of Gila monster saliva. Previous research indicated that a specific chemical found in the saliva of the desert-dwelling venomous lizard had a high affinity for binding to a specific molecule in insulinomas known as the GLP1 receptor. But it wasn’t as simple as collecting vials of reptile saliva to use in the laboratory.

“The saliva substance was not very stable in the human body,” Gotthardt explained.

To solve this problem, researchers developed a more chemically stable synthetic version, known as Extendin, which they then combined with a mildly radioactive tracer used in standard PET scans. From there, they asked 69 adult patients suspected of having insulinoma to undergo the Extendin-PET test. The results were clear: While basic PET scans detected tumors 65% of the time, the new option derived from the Gila monster did so with a 95% accuracy rate. In cases where the Extendin-PET scan was combined with CT and MRI, 13% of insulinoma identifications were solely thanks to the Extendin-PET procedure. Once confirmed, surgeons successfully removed all tumors from affected patients.

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In the future, the team hopes to conduct more research into the benefits of Extendin and how it can be used to treat insulinoma, as well as work to introduce modified PET scans into medical facilities.

“’We believe the new scan can replace all other scans,” Boss said. “… (All) of these patients were completely cured after surgery, although some had been ill for decades.”