Lizard saliva vs. tumours: reality or science fiction?

Surely, saliva isn’t something that should be introduced into medicine, right? It just wouldn’t be hygienic. Well, not quite, according to a study in the Journal of Nuclear Medicine (JNM), it turns out that the saliva of the Gila monster—a reptile found in the deserts of Central and South America—has a unique quality. Its components contain a protein which, when modified, becomes a highly effective tool for detecting pancreatic tumours. The Gila monster resembles a smaller Komodo dragon and is venomous. However, its venom actually lies in its saliva, which happens to also produce a protein called exendin-4. This protein can already be used in diabetes treatment, but when modified and targeted at the pancreas, it activates GLP-1 receptors, which then stimulate insulin production. This allows doctors to identify the areas of the pancreas that are not producing insulin and surgically remove the tumour with greater precision. Before this discovery, the only option was a PET scan - more invasive and far less accurate. Due to this lack of precision, surgery often involved removing the entire pancreas or making exploratory cuts to locate the tumour, increasing the invasiveness of the procedure. By contrast, this new method offers remarkable advantages. It is not only more accurate, enabling surgeons to know exactly which part of the pancreas to remove, but also less invasive, as it works with a small dose of modified exendin-4. What does the detection process involve exactly? First, the protein is made radioactive and then stabilised by binding it to another molecule. It is then targeted at the pancreas, accelerating insulin production in healthy cells. A PET scan is then performed, identifying any tumours with striking precision. A trial was conducted to assess this new technology’s effectiveness. Sixty-nine individuals diagnosed with low blood pressure due to excessive insulin participated; of these, 53 were suspected of having insulinomas. Each underwent both a conventional PET scan and one using exendin-4. The standard PET scan detected 35 tumours; the exendin-4 scan found 50. That’s 17 additional tumours identified using the new technique. What’s more, the protein-enhanced PET scan produced less background noise, making the results cleaner and easier to interpret. Patients also experienced fewer side effects compared to traditional PET scans and earlier versions of this new technique. “I think this work is incredibly valuable in showing how exendin-4 could be used in the diagnosis of insulinoma and potentially replace many current imaging techniques that aren’t as effective,” said lead researcher Peter Choyke. “We just want to spread the technology,” he added. “Everyone should be able to use it, because it truly helps patients.” Efforts are already under way to distribute this technology to labs and hospitals.

By Luca Rocchinotti Maioli, 3L Liceo Scientifico Vittorio Veneto, Milan