CHAPTER EIGHT
The Mother of Krestin
Trametes versicolor HAS THE distinction of being the mushroom from which one of the world’s leading anticancer drugs is derived. The drug is called Krestin. Although Krestin has not been approved for use by the United States’ Food and Drug Administration (FDA), it was the bestselling anticancer drug in Japan for much of the 1980s, with sales top-ping $500 million annually. Krestin was the first mushroom-derived anticancer drug to be approved by the Japanese government’s Health and Welfare Ministry, the equivalent of the United States’ FDA. All healthcare plans in Japan cover members’ purchases of Krestin.
Trametes versicolor came to the attention of the pharmaceutical industry in 1965 when a chemical engineer working for Kureha Chemical Industry Company Ltd. in Japan observed his neighbor attempting to cure himself of gastric cancer with a folk remedy. The neighbor was in the late stages of cancer and had been rejected for treatment by hospitals and clinics. For several months, he took the folk remedy, a mushroom, and then, having been cured, he went back to work. The folk remedy was Trametes versicolor.
The engineer from Kureha Chemical convinced his colleagues to examine the mushroom. The best strain of Trametes versicolor was found and cultivated. Soon PSK, an extract from the mushroom, was born. PSK is the chief ingredient in Krestin. PSK stands for Polysaccharide-K, K being the first letter of Kureha Chemical, the company that developed PSK and Krestin. As Chapter Two explains, a polysaccharide is a chain molecule constructed from sugar units. One-three beta glucan, the type of polysaccharide found in medicinal mushrooms, is especially beneficial to the immune system.
The success of Krestin inspired Chinese researchers to look into and develop an extract from Trametes versicolor of their own. This extract is called PSP. PSP stands for Polysaccharide-Peptide. In biochemistry, a peptide is a compound of low molecular weight that figures in the creation of proteins. PSK and PSP are derived from different strains of Trametes versicolor. What’s more, the extraction methods and fermentation processes of each substance are different. Clinical experimentation with PSP did not begin until the early 1990S, whereas clinical studies of PSK have been conducted since 1978.
Trametes versicolor is found in temperate forests throughout the world and in all fifty states of the United States. It is lovely and is occasionally included in floral displays. In the English-speaking world, the mushroom is known as the Turkey Tail because its fan shape resembles the tail of a standing turkey. It is striped with dark-to-light brown bands that alternate with bands of orange, blue, white, and tan. It prefers to grow on dead logs and has been known to feed on most kinds of trees.
In Latin, the etymology of Trametes versicolor is as follows: Trametes means “one who is thin”; versicolor means “variously colored.” In some literature, the mushroom is called Coriolus versicolor and, rarely these days, Polyporus versicolor, but taxonomists now agree that the mushroom should properly be Trametes, not Coriolus or Polyporus. In China, the mushroom is called yun zhi, or “cloud mushroom.” In Japan it is called Kawaratake, which means “beside the river mushroom.”
The Japanese have long used Trametes versicolor as a folk remedy for cancer. In traditional Chinese medicine, Trametes versicolor is used to treat lung infections, excess phlegm, and hepatitis. The ancient Taoists revered the mushroom because it grows on pine trees. Because pines are evergreens, Taoist priests assumed that the mushroom had the staying power of the pine tree, which never loses its foliage. Taoists believed that Trametes versicolor collects yang energy from the roots of the pine tree, and they prescribed it for patients whose yang energy was deficient.
At the fourteenth annual International Chemotherapy Symposium in 1991, no less than sixty-eight papers about PSK were presented, about a fifth of all papers. In those heady days, it seemed as though PSK and Krestin might unlock the secret to preventing cancer and helping cancer patients recover.
The drug is almost always prescribed to cancer patients who have had a tumor removed and are undergoing chemotherapy or radiotherapy. It is often prescribed for colon, lung, stomach, and esophagus cancer and has no side effects. Chemotherapy and radiotherapy damage the bone marrow and thereby interfere with the production of blood cells, induding white blood cells, which play an important role in the immune system. Following are three recent studies that demonstrate the effectiveness of PSK on cancer patients’ immune systems:
Krestin came under fire beginning in the late 1980s at several medical conventions, where doctors questioned its effectiveness. The substance, it seemed, had been overhyped. The Health and Welfare Ministry in Japan now instructs doctors to use Krestin only as an adjunct to chemotherapyor radiotherapy. The drug by itself is not supposed to be used as a treatment for cancer.
PSK can raise survival rates in cancer patients and prolong their lives. Moreover, the substance is nontoxic. Because the risk to patients of taking PSK appears minimal and the rewards are many, PSK is likely to be an aid in fighting cancer for years to come.
Like PSK, PSP is prescribed to cancer patients to help improve their immune systems before and after surgical treatment, chemotherapy, and radiotherapy. China’s Ministry of Public Health approved PSP as a national class I medical material in 1992. In 1999, PSP was added to the list of medicines whose cost could be reimbursed by government medical insurance and the labor medical insurance programs. What’s more, the National Cancer Research Center in the United States has declared PSP a fungous anticancerous substance. The PSP that has been researched here is derived from a special strain of Trametes versicolor called COY-1. Here are a couple of recent studies concerning PSP: