medicinal mushroomsPhellinus linteus (PL), a mushroom that has been used for many years in traditional Oriental medicine, slows the growth of highly invasive breast cancer cells by a variety of different mechanisms, according to a study published in the April 15 issue of the British Journal of Cancer.

Although new treatments and earlier detection have reduced overall breast cancer mortality, the disease remains the most deadly cancer among women ages 20 to 59. The big challenge to doctors has been in treating the most invasive breast cancers.

In their search for alternatives or additions to traditional cancer therapies such as chemotherapy and radiation, researchers have turned to natural substances with anti-cancer properties. “What I’m looking for are natural products that are able to modulate the invasiveness of cancer cells,” explains Daniel Sliva, Ph.D., senior investigator and Director of the Cancer Research Laboratory at Methodist Research Institute in Indianapolis, Indiana. “We can go back to Mother Nature and find or rediscover something that has been here for a long time and may be effective in the treatment of cancer.”

Dr. Sliva and his colleagues recently turned to their attention to PL. Past research has found that this mushroom species contains complex carbohydrates called polysaccharides, which demonstrate significant anti-cancer effects.

In the current study, Dr. Sliva and his colleagues tested the effects of PL on highly invasive human breast cancer cells in the laboratory. They found that the mushroom extract affects the growth of breast cancer cells in several ways.

First, PL interferes with the cell cycle to prevent cancer cells from proliferating. It blocks the activity of an enzyme called AKT kinase, which is responsible for the uncontrolled cell growth seen in cancer and plays a role in the formation of new blood vessels—a process called angiogenesis. “Blood vessels are important for the nutrition, and therefore the growth, of cancer,” Dr. Sliva explains. “So if we can stop angiogenesis, we will block the delivery of nutrients to cancer, and this will result in the suppression of the growth and metastasis [spread] of cancer.”

Dr. Sliva’s team found that PL also prevented breast cancer cells from forming colonies—a marker of highly invasive cancer, as well as an indicator of its ability to metastasize. And, the mushroom inhibited three crucial events responsible for cancer metastasis: cell adhesion (the ability of the cancer cells to stick together and attach in other parts of the body), cell migration (the ability of cells to move in the body), and cell invasion (the ability of cells to penetrate through the organs in the body). “If you can inhibit one of these three factors…you can stop cancer cells from metastasizing,” Dr. Sliva says.

Once they had demonstrated the effectiveness of PL against invasive breast cancer cells, Dr. Sliva and his colleagues wanted to determine whether it is safe. When they tested it in the lab, the researchers found that PL was not toxic to human cells.

The results of this study still need to be confirmed in animal studies and then human clinical trials. If it is found to be both safe and effective in humans, PL could be used as an adjuvant to chemotherapy and other breast cancer treatments.

Sliva D, Jedinak A, Kawasaki J, Harvey K, Slivova V. Phellinus linteus suppresses growth, angiogenesis and invasive behaviour of breast cancer cells through the inhibition of AKT signaling. British Journal of Cancer. 2008;98:1348-1356.

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