Short-Lived Isotope Opens New Possibilities for Cancer Treatment

A radioisotope of the element actinium is a promising agent for targeted-α therapy to destroy malignant cells, while minimizing the damage to healthy surrounding tissue.

Developed by researchers at Los Alamos National Laboratory (LANL; NM, USA), and in collaboration with the Stanford Linear Accelerator Center (SLAC) Laboratory (SLAC; Menlo Park, CA, USA), targeted-α therapy is based on the radioisotope actinium-225, which has a relatively short half-life of 10 days and emits powerful alpha particles as it decays to stable bismuth. But targeted-α therapy can only become a reliable cancer treatment if actinium securely binds to a chelator, as the radioisotope is very toxic to healthy tissue.

In an attempt to clarify the limited understanding of actinium chemistry, the researchers used X-ray absorption spectroscopy and molecular dynamics density functional theory to investigate actinium coordination chemistry. They were able to determine information about chemical bonds formed by actinium, including what binds to the element, how many atoms are present, and the distances between them. The researchers will now attempt to engineer a chelator carrier molecule that could safely transport actinium-225 through the body to tumor cells. The study was published on August 17, 2016, in Nature Communications.

“Imagine if someone gave you the element iron and nothing was known. That’s almost the same place we were in with actinium, as far as macroscopic chemistry goes. The Manhattan Project scientists used film to see the X-rays released off the sample,” said study co-author Stosh Kozimor, PhD, an isotope chemist at Los Alamos, “but the radioactivity from actinium darkened the film before they could make meaningful measurements. They were only able to get a fingerprint of the actinium compounds that were suggestive of what formed. Beyond that, there isn’t much information in those measurements.”

Actinium (Ac), discovered in 1899, is a radioactive chemical element with the atomic number 89. It was the first non-primordial radioactive element to be isolated. A soft, silvery-white metal, it reacts rapidly with oxygen and moisture in air, forming a white coating of actinium oxide that prevents further oxidation. One ton of natural uranium in ore contains about 0.2 milligrams of actinium-227. Owing to its scarcity, high price, and radioactivity, actinium has no significant industrial use.

Related Links:
Los Alamos National Laboratory
Stanford Linear Accelerator Center Laboratory