University of Virginia Health System

U.VA. RESEARCHERS FIND ANOTHER CLUE TO MYSTERY OF MELANOMA

In the study, mice were injected with a vaccine for melanoma that included an antigen known to be a target of the immune response in people with melanoma. Antigens are markers on cells that act as microscopic flags. The body's immune system is trained to read these flags, which show which cells are normal and which have been infected with viruses or have become cancerous. The mice carried a gene for a human protein that researchers thought would enable them to correctly interpret the flag. A significant immune response to the antigen was observed, showing that this was the case.

We think that the ability to make an immune response to this antigen may be an important aspect of a patient's ability to control tumor growth. We hope that by learning how to improve immune response, we can help patients with melanoma fight the disease, said Victor Engelhard, professor of microbiology at U.Va. and leader of the study team.

Developing a vaccine to combat melanoma is especially difficult because the antigen for melanoma is also present on normal skin, and the immune system is usually tolerant to antigens found in normal cells. A vaccine must be able to stimulate the immune system to fight cancer cells expressing the antigen but not kill regular skin cells.

The researchers compared mice that were engineered not to have this antigen to normal mice and found that the presence of the antigen reduced the immune response; however, there was still some response in normal mice. The paper describes ways to improve and utilize the response. Engelhard said his team hopes these findings will be applicable to humans.

Previous work by Engelhard and others at U.Va. led to the development of early vaccines for melanoma. Currently, several clinical trials of these vaccines are being conducted at U.Va. and other academic medical centers in the U.S and abroad. Early trials have shown significant immune responses in melanoma patients. The results of this and future research will be incorporated into the vaccines as new trials begin.

The work we're doing at U.Va. in melanoma is progressing very quickly. The results of our research directly impact the vaccine used in the next trial, so we are continually improving the treatment patients receive, Engelhard explained.

Melanoma is the most serious and most common type of skin cancer. It occurs when the pigment cells, which control skin color, become malignant. According to the National Cancer Institute, the number of people who develop melanoma is increasing faster than any other cancer. The number of new cases of melanoma has more than doubled in the U.S. in the past 20 years.

April 13, 2000