They have found that a topical compound made of black raspberries markedly slows the growth of that cancer in mice who have been exposed to ultraviolet B, commonly known as UVB radiation, the most dangerous in the solar spectrum."In terms of shutting down the inflammatory response, we've never seen anything like it," said Anne VanBuskirk, senior author of the study that was presented earlier this year at the annual meeting of the American Association of Cancer Research. VanBuskirk is an assistant professor of surgery at the university's college of medicine.
UVB, she explained, is believed to be the bad guy in the sun's rays that causes sunburn. Moreover, it also is thought to be the culprit that causes most of the nonmelanoma skin cancers diagnosed annually in this country.
But how did the sweet black raspberry become the subject of inquiry in the first place? It seems Professor Emeritus Gary Stoner long had been fascinated with the black raspberry, a common Ohio crop. Stoner's research focus had been on cancer chemoprevention (meaning the use of an external agent to prevent or medicate cancer).
In conversations with Stoner, VanBuskirk, whose doctorate is in immunology, learned he had not tried a topical application of black raspberries in his research. That was three years ago.
A graduate student under VanBuskirk, she recalled, was particularly interested in researching natural products in the fight against cancer. F. Jason Duncan became the lead author of the study after he and his mentor exposed mice to UVB rays, then treated them with either an over-the-counter gel or one containing the concentrated powder made from the berries. The mice treated with the nonberry gel experienced a 67 percent thickening in their skin because of edema caused by the UVB rays.
Researchers know that cells move in quickly when sunburn occurs - the process is called neutrophil infiltration - and the mice treated with nonberry gel experienced a rise of 500 percent in an enzyme called myeloperoxidase, a marker of neutrophil activity.
By contrast, the mice treated with the black raspberry gel experienced only a 20 percent thickening of the skin, and the myeloperoxidase levels rose only 37 percent. In a follow-up experiment, researchers learned that black raspberry gel reduced the size and number of tumors in mice overexposed to UVB light.
While the lay person's extrapolation from that information may be to rub crushed black raspberries on sunburned skin, it would be wrong.
VanBuskirk laughed heartily before replying, "You could be pretty sure smashed raspberries will turn your skin blue or purple, but it won't really help. But the interesting thing about the extract we used on the mice is that it concentrates the active ingredients of the berries but it didn't turn their skin blue."
VanBuskirk is hopeful that clinical trials on humans may begin in the next couple of years. She works closely with a group that includes, among others, dermatologists who are anxiously awaiting those trials, she said.
"(Organ) transplant patients are at high risk for skin cancer because of the anti-rejection medication they have to take for their entire lives," she explained. "It allows them to live with the new organ, but the way it allows that is it suppresses the immune system, which can put them at high risk for getting colds, bacterial infections and other viruses.
"It also impairs their ability to fight off cancer. Their susceptibility for two cancers is really increased. Lymphoma, their risk increased 20-fold. For nonmelanoma skin cancer, particularly squamous cell, the risk is 65- to 250-fold increased. So there is much to remember about sun protection."
For the general population, the research findings also are good news.
"If repeated studies bear out these findings," VanBuskirk explained, "it could mean that one day we may be seeing a topical gel that could be used after you get sunburned - one that not only eases pain, but also lessens any sun damage you might have already suffered."