Japan develops radiation therapy directly in cancer cells to destroy tumors.

Scientists at RIKEN Japan have developed a technique to treat different types of cancer by generating alpha radiation in cancer cells to kill without harming healthy tissue.

A research team led by Professor Katsunori Tanaka at the RIKEN "Cluster for Pioneering Research" (CPR) Japan and Hiromitsu Haba at the RIKEN Nishina Nuclear Accelerator Science Center (RNC) has developed a new technique that is capable of generalizing certain types of cancer with fewer adverse side effects than current methods.

SciTech Daily cited a scientific report published on June 27 in the journal Chemical Science, saying that a group of Japanese scientists in a study showed that tumors in mice grew almost three times smaller and the survival rate was 100% after just one compound injection. The compound is designed to emit tiny amounts of alpha radiation from within the cancer cells, thereby killing the cancer cells without harming healthy tissues.

The side effects of standard chemotherapy and radiation therapy can be devastating, and the ability to eliminate all cancer cells in the body is not guaranteed, significantly when the cancer has metastasized and spread throughout the body.

Therefore, the goal of most current research is to find a way to specifically target cancer cells so that the treatment affects only the tumors. Some targeted therapies are being used, but not for all cancers.

"One of the biggest advantages of the new approach we propose is that it can be used to treat a wide range of cancers without the need for any vectors that target a selection marker such as antibodies or peptides," said Professor Tanaka.

The new technique, developed on introductory chemistry, exploits the tendency of cancer cells to accumulate a compound called acrolein and introduce into the cancer cells a molecule, the radioisotope astatine-211, which emits alpha radiation upon decay.

Several years ago, Prof Tanaka's team used a similar technique to detect individual breast cancer cells. Scientists attach a fluorescent compound to a specific type of azide (energy-rich molecule), an organic molecule with a group of three terminal nitrogen (N3) atoms.

When azide and acrolein meet in a cancer cell, the substances react, and the fluorescent compound is anchored to structures within the cancer cell. Since acrolein is barely present in healthy cells, the technique acts like a probe that causes cancer cells to glow in the body.

In the new study, the team aimed to kill those cells instead of simply detecting cancer cells—simple logic. Instead of attaching an azide to a fluorescent compound, the team secured the organic material to a radioactive substance that could kill cells without harming surrounding cells.

The scientists selected astatine-211, a radioactive isotope that emits small amounts of radiation in the form of alpha particles when decaying over more than eight hours. Compared with other modes of radiation therapy, alpha particles are a bit more dangerous, but the particles can only travel about 1/20 mm and be stopped by a piece of paper. Theoretically, when astatine-211 anchors inside cancer cells, the alpha particles emitted will destroy the cancer cells.

After the team figured out the best way to attach astatine -211 to the azide probe, they performed proof-of-concept experiments to test their theory.

The team transplanted human lung tumor cells into mice, testing the treatment under three conditions: simply injecting astatine-211 into the tumor, injecting the astatine-211-azide probe into the tumor, and injecting the astatine-211-azide search into the bloodstream.

The scientists realized that, without targeting, the tumors continued to grow, and the mice could not survive. As expected, tumors grew almost three times slower when the azide probe was used, with more mice staying, 100% when injected into the cancer and 80% when injected into the bloodstream.

"We found that a single injection of the tumor with 70 kBq of radioactive material is extremely effective in targeting cancer treatment and killing tumor cells," said Mr. Tanaka. "Even when we injected the therapeutic compound into the bloodstream, we achieved the same results. "This result means we can use injections into the bloodstream to treat very early cancers even when we don't know where the tumor is."

The fluorescent probe version of this technique has been tested in clinical experiments to detect and diagnose cancer at the cellular level. The following research stage is to find a partner and start a clinical trial using a new human cancer treatment method.