Prostate cancer: Watchful wait or ...( PHILADELPHIA Researchers at the Uni...)

PHILADELPHIA Researchers at the University of Southern California have developed a prostate cancer vaccine that prevented the development of cancer in 90 percent of young mice genetically predestined to develop the disease. In the February 1 issue of Cancer Research, they suggest the same strategy might work for men with rising levels of PSA (prostate specific antigen), a potential diagnostic indicator of prostate cancer.

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

Now, men with rising PSA levels but no other signs of cancer are advised watchful waiting no treatment until signs of the cancer appear, Kast says. But what if instead of a watchful wait, we vaccinate" That could change the course of the disease.

The study findings also represent a new way to think about the use of therapeutic prostate cancer vaccines, Kast says. Vaccines now in testing are designed to treat men whose cancers are advanced and unresponsive to therapy, and results have offered limited clinical benefit, he says. This novel approach targets the precancerous state with the aim of preventing cancer from developing, he says.

The Kast teams preventive vaccine is designed to mount an immune response against prostate stem cell antigen (PSCA), the protein target of some therapeutic vaccines under development. PSCA, a membrane protein, is over-expressed in about one-third of early-stage prostate cancers, but expression ramps up in all prostate tumors as they grow and advance. PSCA is also expressed at low-levels in normal prostate gland tissue as well as in the bladd
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