Lotion may prevent cancer in sun-damaged skin
We pay a price for our love affair with the sun. The cumulative damage from years of exposure is the chief culprit behind most skin cancers. Although sunscreens can block the sun’s harmful rays, nothing can patch skin cells that have already been injured -- until now, researchers say.
An experimental lotion derived from a yeast enzyme may work like a “morning-after” cream, repairing mutant cells before they turn cancerous.
“Skin cancer has become a major epidemic,” says Dr. John DiGiovanna, a dermatologist at Brown University Medical School in Providence, R.I. “This drug potentially has great promise and could be used as a preventive for skin cancer.”
About 1.3 million Americans each year are diagnosed with basal or squamous cell cancer, the two most common types of skin cancer, which are easily cured if caught early enough. And 51,000 more are stricken with the deadlier melanoma, and about 10,000 people die from skin cancer, mostly from melanoma.
The sun’s scorching ultraviolet rays trigger cancer by causing genetic mutations in skin cells and also interfere with the immune system’s ability to ward off cancer. The new cream, Dimericine, contains a DNA-repair enzyme called T4 endonuclease V. The enzyme is carried in liposomes, tiny, oily pouches that penetrate the skin’s surface and enter cells. Research suggests that the enzyme then mends the defective genes and keeps the immune system intact.
In a 2001 study, the cream was tested on 30 people with a rare inherited disease called xeroderma pigmentosum, or XP. Sufferers blister after being in the sun for a few seconds; they lack a key enzyme needed to repair sun-damaged DNA and develop skin cancer at 1,000 times the normal rate. After applying the cream to their faces and arms for a year, participants experienced a 30% reduction in new basal cell carcinomas and a 68% reduction in new actinic keratoses, precancerous lesions that affect 1 in 6 Americans.
Other people may benefit from Dimericine, too. The disease is “just an accelerated version of what’s happening to all of us,” says Daniel B. Yarosh, a molecular biologist and president of AGI Dermatics of Freeport, N.Y., which makes the cream. “We’ve chosen patients who are most vulnerable to skin cancer to do our first studies. But in the future, this might be something everyone routinely slathers on.”
The National Cancer Institute is sponsoring tests of Dimericine on 100 people who have had a kidney transplant and are taking anti-rejection drugs that compromise their immune systems. Nearly half develop skin cancer within 10 years, whereas the average person has a lifetime risk of about 16%.
“The tumors that develop in transplant patients behave much more aggressively, too,” says Dr. Craig A. Elmets, a dermatologist at the University of Alabama at Birmingham who is testing the drug.
Although AGI Dermatics plans to apply for federal approval to treat XP patients with Dimericine, the drug won’t be available for a couple of years. In the meantime, says Elmets, sunscreen and limiting sun exposure are still the best ways to avoid skin cancer. So don’t throw away the sunscreen just yet.
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Today’s therapies
Several therapies are currently used to treat precancerous lesions and early-stage skin cancers. Normally, actinic keratoses (precancerous growths) and superficial basal cell cancers can be frozen off with liquid nitrogen, though the treatment can cause several weeks of redness and irritation.
Repeated applications of several creams, such as Carac, Efudex and Solaraze, can remove keratoses patches, too. Some dermatologists also use retinoid acids, such as the acne medication Retin-A and Aldara, a topical lotion to combat genital warts, to eliminate keratosis lesions. These creams work by causing the abnormal cells on the top layer of skin to die off.
