LONDON (Reuters) - Extracts from a mushroom used for centuries in Eastern Asian medicine may stop breast cancer cells from growing and could become a new weapon in the fight against the killer disease, scientists said on Tuesday.

Laboratory tests using human breast cancer cells show the mushroom called Phellinus linteus has a marked anti-cancer effect, probably by blocking an enzyme called AKT. AKT is known to control signals that lead to cell growth.

Phellinus linteus -- called song gen in Chinese medicine, sang-hwang in Korean and meshimakobu in Japanese -- has previously been shown to have anti-tumor properties on skin, lung and prostate cancer cells.

The new research on breast cancer, however, marks the first time that scientists have started to understand how it works.

Dr Daniel Sliva of the Methodist Research Institute in Indianapolis said the mushroom extract reduced uncontrolled growth of new cancer cells, suppressed their aggressive behavior and blocked new tumor-feeding blood vessels.

"We're not yet able to apply this knowledge to modern medicine, but we ... hope our study will encourage more researchers to explore the use of medicinal mushrooms for the treatment of cancer," he said.

The findings were reported in the British Journal of Cancer.