Jennifer Gale(847) 240-1730[email protected]
Julie Bremer(847) 240-1743[email protected] EMBARGOED UNTIL APRIL 25, 2001
THE FUTURE OF CHEMOPREVENTION LOOKS BRIGHT: PROMISING NEW WAYS TO PREVENT SKIN CANCER AND PHOTOAGING
NEW YORK (April 25, 2001) - While 80 percent of sun damage occurs before age 18, the results of this damage from ultraviolet (UV) radiation appears in the form of photoaging of the skin and the development of skin cancer years later. At first a person may notice fine lines or wrinkles around the eyes or, in the worst case, the development of a suspicious growth that could be cancerous. Although sun avoidance and the use of sunscreen is designed to block the first step in the sun damage process, dermatologists are now conducting research into how the development of skin cancer and photoaging can be altered between the time the initial damage occurs and the time it appears on the skin.
Speaking today at the American Academy of Dermatology's Melanoma/Skin Cancer Detection and Prevention Month Press Conference, dermatologist James M. Spencer, MD, Associate Professor, Department of Dermatology, Mount Sinai School of Medicine, New York, discussed common systemic and topical products that could soon hold the key in effectively preventing skin cancer and photoaging.
Chemoprevention refers to the prevention of photoaging or skin cancer by the use of pharmacologic agents that inhibit or reverse the photoaging process or skin cancer formation. "There are many points beyond UV absorption where a chemopreventative agent might work, and that's exciting because it gives researchers the ability to test many different agents in several different stages of the sun damage process," said Dr. Spencer.
One chemopreventative agent that has proven effective is vitamin A and its derivatives, also known as retinoids. Although retinoids clearly do not function as sunscreens, they seem to work later in the sun damage process after UV exposure has occurred. One large clinical trial involving 2,297 patients investigated the chemopreventative effects of vitamin A. Patients enrolled in the study had a history of more than 10 actinic keratoses, or pre-cancerous lesions, less than three skin cancers, and were considered at moderate risk for the development of new skin cancers. Oral vitamin A was given at a dose of 25,000 IU, or international units, daily for up to five years. As a result, it was found that there was a significant reduction in the formation of squamous cell skin cancer but not basal cell skin cancer.
"This large, randomized placebo-controlled phase III trial definitely showed the chemopreventative efficacy of vitamin A in moderate risk patients," explained Dr. Spencer. "However, when a follow-up study was conducted of patients with a history of four or more skin cancers who were considered high risk, no protective effect of oral vitamin A administered at the same dosage was seen. Currently, vitamin A and its derivatives are the only group of chemopreventative agents that have clearly demonstrated their effectiveness."
Diet is often linked to many diseases, such as cancer, and recent studies have examined dietary fat in humans and experimental animals. One study involving humans found that lowering the percentage of fat in the diet while keeping total calories constant resulted in fewer new actinic keratoses during the study period and a significant reduction in the formation of new skin cancers.
In one animal study, mice fed with unsaturated fat were compared to mice fed saturated fat. It was found that fewer skin tumors developed in the mice fed saturated fat. Similarly, in studies using the South American opossum - an animal model for melanoma - a saturated fat diet produced fewer melanocytic tumors than a diet containing unsaturated fats, but had no effect on the development of squamous cell skin cancers.
"While diet is often mentioned as a chemoprevention strategy, it is a controversial area with just as many reports suggesting diets high in fruits and vegetables result in fewer internal cancers as there are large studies reporting no protective effect," cautioned Dr. Spencer. "The question with dietary studies is whether the effect seen is the effect of nutrients, such as fat and carbohydrates, or non-nutrients that may only be present in trace amounts."
Two promising groups of chemopreventative agents derived as non-nutrients from plants include the polyphenolic antioxidants - such as grape seed extracts - and the isoflavones - such as soybean extracts. Both grape seed extracts and soybean extracts are found in topical products at health food stores and are available in some cosmetics.
Green tea, which is the second most widely consumed beverage in the world following water, contains polyphenolic antioxidants in its extract that has been investigated for its cancer preventing properties. According to a study in the March 2001 issue of the Journal of the American Academy of Dermatology, a nutrient found in green tea known as Epigallocatechin-3-gallate (EGCG), which constitutes 30 percent to 40 percent of its dry weight, has emerged as a leading candidate for chemoprevention studies.
"While its effect on internal malignancies has been mixed, green tea extract containing this polyphenolic antioxidant and its derivatives has been shown to inhibit the growth of human melanoma cell lines in tissue culture and to inhibit UV-induced skin cancer formation in mice when applied topically or given orally," explained Dr. Spencer.
The isoflavones is another group of compounds with antioxidant activity and anti-carcinogenic effects that are emerging as candidates for chemoprevention. Genistein, a compound of isoflavones found in soybeans, works as a potent antioxidant that has been found to inhibit the growth of tumors in mice when given orally or applied topically. In another study, Genistein has also been shown to inhibit an enzyme involved in photoaging.
"Topical cosmetic products containing soybean extracts are already becoming available, with the promise of chemoprevention of sunburns, photoaging, and skin cancer," said Dr. Spencer. "While initial studies of these compounds have shown considerable potential as chemopreventative agents, consumers need to be aware that more testing needs to be conducted before they can be considered as true cancer-fighting agents."
Another promising group of chemopreventative agents that most people already have in their medicine cabinets is aspirin and the non-steroidal, anti-inflammatory drugs. These compounds function by inhibiting COX, an enzyme that regulates the prostaglandin group of hormones.
A new class of medications that selectively inhibits COX II has been developed and holds great promise for the chemoprevention of skin cancer. Recent studies have shown that celecoxib, a specific COX II inhibitor developed as a treatment for arthritis, can significantly reduce skin cancer formation when given before or during ultraviolet light exposure. In addition, when given after UV exposure and after the first skin cancer appears, celecoxib can inhibit the development of further tumors.
"The idea that such a common group of medications so widely available may provide effective chemoprevention of cancer makes this area of research particularly exciting," said Dr. Spencer. "I think in the next few years we'll be seeing many promising new candidates emerge in the fight against skin cancer and photoaging."
American Academy of Dermatology, founded in 1938, is the largest, most influential, and most representative of all dermatologic associations. With a membership of over 13,000 dermatologists worldwide, the Academy is committed to: advancing the science and art of medicine and surgery related to the skin; advocating high standards in clinical practice, education, and research in dermatology; supporting and enhancing patient care; and promoting a lifetime of healthier skin, hair and nails. For more information, contact the AAD at 1-888-462-DERM or www.aad.org.
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