WASHINGTON, Feb. 14 (Xinhua) -- Small molecules that specifically restrain a selenium-containing enzyme in the human body may be a tool to fight cancer, a study published in a U.S. medical journal on Wednesday said.

The study published in Science Translational Medicine said researchers at Karolinska Institute in Sweden, one of the world's largest and most prestigious medical universities, treated cancer in mice with these molecules, and then observed rapid tumor-killing effects.

They hope that this new principle for cancer treatment can be extended to treat cancer in humans.

Selenium is a chemical element that is an essential micronutrient. A selenium-containing enzyme, called TrxR1, can be used to support the growth of various cells and protect them from oxidative stress.

Oxidative stress is the imbalance between the production of free radicals, which are highly reactive with other molecules, and the body's ability to counteract or to repair the resulting damage.

However, in several forms of cancer raised levels of TrxR1 could be detected.

Researchers analyzed almost 400,000 different molecules to find new ones that would more specifically control TrxR1 and found three different types which proved to be active as anti-cancer medicines.

The researchers effectively treated over 60 different types of cancer cells under laboratory conditions with these molecules.

Normal cells, however, were much less sensitive to these molecules.

"This effectiveness against cancer may be a result of cancer cells' seemingly greater sensitivity to oxidative stress when compared to normal cells, which in turn can be utilized in cancer therapy," Prof. Elias Arner at Karolinska Institute, who led the study, said.

"This seems to work in mouse models and we are therefore hopeful that this principle for treatment can be developed for humans, even if this will require many years of further research," he added.