A doctor exams mammogram x-rays in a file photo. REUTERS/Eric Gaillard

HONG KONG (Reuters) - Scientists in Japan have identified an enzyme which appears to suppress breast cancer and they hope the finding will spur new therapies to control the second most common cancer in the world.

At issue is the enzyme CHIP, which experts say can stunt cancer growth by degrading a number of cancer-causing proteins. The enzyme occurs naturally in human breast tissue.

In an article published in Nature Cell Biology, the scientists said they injected two kinds of human breast cancer cells into mice. One set carried the CHIP enzyme and the other was without the chemical.

Tumors in the first group of mice with the CHIP enzyme were far smaller than the one without the enzyme, Junn Yanagisawa at the University of Tsukuba’s Graduate School of Life and Environmental Sciences in Japan told Reuters.

The same results were seen in a parallel experiment using a more aggressive line of human breast cancer cells, he added.

“Our conclusion is that we have found that CHIP protein prevents breast tumor growth and metastasis,” Yanagisawa said.

Metastasis occurs when cancer spreads from its site of origin, which challenges therapy and may even result in death.

“In breast tumor treatments, measurement of the CHIP protein levels in the tumors may be valuable information for the treatment. Furthermore, designing a new therapy that increases CHIP protein levels or its activity could be useful for breast tumor treatment,” Yanagisawa said.

Breast cancer is the second most common form of cancer, after lung cancer. In 2005, it killed 502,000 people worldwide, or almost 1 percent of all deaths.