Radioactive gel
Pancreatic cancer accounts for only 3.2% of all malignant tumors, but it ranks third among the causes of death from cancer. It is very difficult to treat, because cancer cells tend to develop aggressive genetic mutations that make them resistant to many drugs, and it is usually diagnosed very late, when metastases have already appeared.
Currently, chemotherapy followed by radiation therapy is used to treat pancreatic cancer. Chemotherapeutic drugs are needed to keep cancer cells at a stage vulnerable to radiation therapy for a longer period. Unfortunately, radiotherapy has no effect until a certain dose of ionizing radiation accumulates in the tumor. It can be very difficult to achieve this without serious side effects.
Another method of treating pancreatic cancer is brachytherapy, which is the implantation directly into the tumor of an ionizing radiation-generating substance enclosed in a titanium case. But since titanium blocks all rays except gamma rays, which spread far beyond the tumor, the implant can remain in the body only for a short period of time and must be removed before damage to the surrounding tissues negates the desired positive effect.
To circumvent these problems, bioengineers from Duke University have developed a new radiation source delivery system using elastin-like polypeptides (ELP), which are synthetic chains of amino acids forming a gel-like substance with desired properties.
ELPS exist in a liquid state at room temperature and form a stable gel-like substance at body temperature. When injected into the tumor, together with the radioactive element ELP, a depot containing radioactive atoms is formed. In this case, the researchers decided to use the radioactive isotope of iodine (iodine-131), because it has been used for medical purposes for decades, and its biological effects are well studied.
Iodine-131 emits beta rays that penetrate through the biogel and direct all its energy into the tumor without getting into the surrounding tissues. Over time, the ELP depot decomposes into its constituent amino acids and is absorbed by the body – but not before iodine-131 decays to harmless xenon.
The depot of ELP reliably holds iodine-131 and prevents its leakage. Beta radiation, in turn, improves the stability of the ELP biogel. This helps the depot to last longer and collapse only after the radiation is used up.
ELP implantation with a radioisotope was tested in combination with the chemotherapy drug paclitaxel for the treatment of mouse models of pancreatic cancer. Experiments have shown a response to treatment in all animals, while tumors were completely eliminated in 80% of cases. The tests also revealed no obvious side effects other than those associated with chemotherapy.
Currently, researchers are planning trials on large animals to show that treatment can be carried out using existing endoscopy tools and methods that doctors are already trained in. If successful, phase 1 of clinical trials on volunteers will be launched.
Article by J.Schaal et al. Brachytherapy via a depot of biopolymer-bound 131I synergizes with nanoparticle paclitaxel in therapy-resistant pancreatic tumours is published in the journal Nature Biomedical Engineering.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on materials from Duke University: Gel-Like, Radioactive Implant Obliterates Pancreatic Cancer in Mice.