Gila monsters are odd lizards, both from a physical and chemical standpoint. Most people can at least recognize the 1.5-foot-long lizard due its striking bumpy, pink and black scales, squat body, and trademark stubby tail. Those aren’t their only unique features—they are only one of two known lizard species in the world capable of producing venom. While receiving a neurotoxic poison-filled bite is rarely fatal, it isn’t pleasant, and can cause considerable pain, edema, nausea, and vomiting. But inside the Gila monster’s spit is also a substance that is now showing major promise in helping detect extremely hard-to-find pancreatic tumors.
On rare occasions, beta cells responsible for producing insulin in the pancreas can malfunction and form small tumors known as insulinomas. While comparatively benign, these growths can still lower someone’s blood sugar levels due to the overproduction of insulin. This issue is particularly problematic for people with diabetes, since it can result in low energy and even fainting. What’s more, the tumors are usually smaller than an inch in size, making them difficult to locate and diagnose. Now, however, a novel PET scan variant appears to accurately assess insulinomas, thanks in large part to the chemical complexities of Gila monster spit.
Before the lizard-inspired solution, identifying patients with insulinoma was extremely difficult for medical teams. In many instances, it takes a long time to confirm their existence.
“It’s a very challenging disease,” Marti Boss, first author of a new study published in The Journal of Nuclear Medicine, said in a statement. “We can perform blood tests, but they can’t confirm if a tumor is the cause or where it’s located. Various scans like CT, MRI, and PET are available, but don’t always show the insulinomas.’
“In the past, surgeons would start cutting away portions of the pancreas until they found the tumor. If it was at the end, the entire pancreas would be gone,” added Martin Gotthardt, a nuclear medicine professor and study co-author. “You can live without a pancreas, but you’d struggle with severe diabetes and would constantly have to manage your blood sugar. So, a better scan was urgently needed.”
Gotthardt and Boss knew of the promising utility of Gila monster saliva. Previous research had indicated a specific chemical substance found in the venomous, desert-dwelling lizard’s spit possessed 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 a lab.
“The substance from the saliva wasn’t very stable in the human body,” Gotthardt explained.
To solve this issue, 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 with suspected insulinoma to undergo the Extendin-PET scan. The results were clear—while the basic PET scans detected tumors 65 percent of the time, the new, Gila monster-derived option did so with a 95 percent accuracy rate. In instances where the Extendin-PET scan was combined with CT and MRI scans, 13 percent of those insulinoma identifications were solely thanks to the Extendin-PET procedure. Once confirmed, surgeons successfully removed all tumors in the affected patients.
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Moving forward, the team hopes to conduct further research into the benefits of Extendin and how it can be used to treat insulinoma, as well as work to introduce the modified PET scans into medical facilities.
“‘We believe the new scan can replace all other scans,” Boss said. “… [A]ll those patients were completely cured after surgery, even though some had been sick for decades.”
