The Fight Against Prostate Cancer Progresses

By Meghan Yost
Ivanhoe Health Correspondent

ORLANDO, Fla. (Ivanhoe Newswire) -- Good news for men: a new prostate cancer vaccine proven powerful in mice may also prevent the disease in humans.

Researchers at the University of Southern California have created a vaccine that prevented prostate cancer in 90 percent of mice genetically predisposed to developing it. After one year, only two of the 20 mice given the vaccine had developed prostate cancer while all of the mice who did not receive it died.

“By early vaccination, we have basically given these mice life-long protection against a disease they were destined to have,” W. Martin Kast, Ph.D., lead researcher and a professor of Molecular Microbiology and Immunology and Obstetrics and Gynecology at the Norris Comprehensive Cancer Center in Los Angeles, Calif., was quoted as saying. “This has never been done before and, with further research, could represent a paradigm shift in the management of human prostate cancer.”

According to Eric Klein, M.D., Head of the Section of Urologic Oncology at Glickman Urological and Kidney Institute in Cleveland, Ohio, prostate cancer is the most common visceral cancer with roughly 230,000 new cases a year. “That number is anticipated to reach over 400,000 cases a year by 2015, as the baby boomers age,” Dr. Klein told Ivanhoe.

Unlike other prostate cancer vaccines currently being tested, this vaccine targets the disease in its precancerous state to prevent it from ever developing. The vaccine works by priming the body to attack prostate stem cell antigen (PSCA), a protein that amplifies during the early stage of prostate cancer and even more as the tumor grows.

Currently, men with increasing PSCA levels but no other indications of cancer do not receive any treatment. Now, instead of waiting for the cancer to brew, the new vaccine has the power to stop it in its tracks.

The vaccine involves a two-step process. First, a fragment of DNA is administered to cause an increase in PSCA and alert the immune system. Two weeks later, a booster shot of a modified horse virus is injected to deliver the PSCA gene.

“Confronting the immune system in two different ways forces it to mount a strong response,” Dr. Kast explained.

“It won’t be many, many years before we know whether [this vaccine] is feasible to do in humans. Therefore, it’s still important that men be screened for prostate cancer. In particular, men who are at high risk of prostate cancer, including African Americans and men who have a family history [of the disease], should be screened at an earlier age,” Dr. Klein said.

SOURCE: Ivanhoe interview with Eric Klein, M.D., Cancer Research, 2008;68:861–869