Researchers tie skin creams to cancer in mice

In an accidental discovery, Rutgers University scientists found that common moisturizers appeared to cause skin cancer in mice.

The products increased the incidence of two non-melanoma skin cancers - squamous cell and keratoacanthoma. Though doctors say the findings might not extend to humans, they raise concerns about dozens of skin products that have not been tested for carcinogenicity.

"We tested four different creams and found that all four of them increased tumor formation," said lead researcher Allan Conney, director of the Laboratory for Cancer Research at Rutgers University School of Pharmacy.

The study was published yesterday in the Journal of Investigative Dermatology.

About a million people a year are diagnosed with non-melanoma skin cancers in the United States, according to recent studies. While not as deadly as melanoma, squamous cell cancer is much more common and does sometimes metastasize and kill people.

"It's an interesting study in that it helps increase our awareness of the possibility of other factors that can influence the occurrence of skin cancer," said Philadelphia dermatologist Susan Taylor.

But she's not telling patients to throw away their skin creams just yet. "Mouse skin is very different from human skin," she said.

"It's critically important that we don't jump to the conclusion that moisturizers cause cancer."

Conney said he and his colleagues did not set out to investigate skin creams. They were following up on earlier work showing that caffeine fought skin cancer in mice by encouraging abnormal cells to die off.

To see if the findings extended to people, they were trying to find a practical way to apply the caffeine to skin. "We wanted to put the caffeine into some kind of an ointment or cream," he said.

He originally chose Dermabase cream to use as a base, since it seemed reasonably neutral. But before adding the caffeine, he decided to see if the cream alone had any influence on the mice.

For their experiments, they used specially bred hairless mice that were subjected to 20 weeks of UVB radiation. The radiation was meant to simulate the damage that people accumulate though years of tanning and sunburning.

Conney said the Dermabase proved to be carcinogenic, as were the next three products they tried: Dermovan, Eurecin, and Vanicream. The effect was significant; cream-treated mice were getting 60 percent to 100 percent more tumors than control animals treated with plain water.

Mark Mitchell, a spokesman for Healthpoint Ltd., said the company's Dermovan was not a retail product but a vehicle provided to dermatologists into which they could put active ingredients.

It never had any safety issues, he said. Dermovan was discontinued several years ago because it was a small-volume product.

Pharmaceutical Specialties Inc., the maker of Vanicream, said in a statement that their product had been safely used for nearly 30 years and that aspects of the study were "of doubtful significance."

Beiersdorf Inc. also issued a statement, saying its moisturizer, Eucerin Original Crème, had been on the market for more than 100 years and was a dermatologist-recommended brand.

Paddock Laboratories Inc., maker of Dermabase, did not respond.

Conney said the ingredients that raised suspicion for him were sodium lauryl sulfate and mineral oil, which had shown some adverse effects in other experiments. With the help of drugmaker Johnson & Johnson, he created a cream that lacked these ingredients and found it did not increase skin cancer in similar mouse experiments.

Conney said that his mice are susceptible only to squamous cell cancers and keratoacanthomas, but that for reasons researchers don't fully understand, the mice don't get basal cell cancer, which is more common, or melanoma, which is more lethal.

Conney and the other dermatologists agreed that a number of epidemiological studies show non-melanoma skin cancers are on the rise. That trend has been attributed to tanning beds, the depletion of the ozone layer, and people spending more time outdoors. Skin cancers diagnosed now may result from sun damage sustained back in the 1970s, he said, before there were good sunscreens.

But there's still no definitive explanation for the increased cancer incidence.

Other dermatologists were skeptical that the use of skin products had much to do with it. "It's a super-interesting paper in the sense that it's addressing something that's part of our everyday lives," said dermatologist James Spencer of St. Petersburg, Fla. "But it's hard to believe there's a chemical in these moisturizers that acts as a carcinogen the way cigarettes do."

Philadelphia's Taylor said that if skin creams and other cosmetics were a significant cancer cause, we should expect to see more cases of non-melanoma skin cancer in women, who use such products much more than men. But men get skin cancer just as often as women.

Still, surprisingly little is known about the cancer-causing potential of common skin products. "Moisturizing creams and other cosmetics actually have no toxicology testing requirements," said David Cragin, an associate professor of toxicology at the University of the Sciences in Philadelphia.

"Many of the cosmetics companies used to do extensive testing to protect their customers," he said, but they scaled back such voluntary tests after protests from animal-rights groups and an increasing consumer demand for products not tested in animals.