Ran across the following today. Sounds promising.....

Fred

USC team develops promising vaccine against prostate cancer

03/07/08

USC researchers 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 Feb.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
study's lead investigator, W. Martin Kast, a professor of Molecular
Microbiology and Immunology at the USC/Norris Comprehensive Cancer
Center and the Keck School of Medicine of USC. "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 said. "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 said. 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 said. This novel approach targets the precancerous state
with the aim of preventing cancer from developing, he said.

The Kast team's 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 bladder, colon, kidney and stomach.

The researchers created a prime-boost vaccination scheme using two
kinds of vaccines and tested it in 8-week-old mice that were
genetically altered to develop prostate cancer later in life. The
first vaccine simply delivered a fragment of DNA that coded for PSCA,
thus producing an influx of PSCA protein to alert the immune system.
The booster shot, given two weeks later, used a modified horse virus
to deliver the PSCA gene.

"Confronting the immune system in two different ways forces it to
mount a strong response," Kast said.

In the experimental group, two of 20 mice developed prostate cancer at
the end of one year, but all control mice had died of the disease.
Researchers found that mice in the experimental group had all
developed very small tumors that did not progress. "There were tiny
nodules of prostate cancer in the mice that were surrounded by an army
of immune system cells," Kast said. "The vaccination turned the cancer
into a chronic, manageable disease."

The vaccination strategy also works with other antigens, Kast said.
The researchers recently tried another prostate cancer membrane target
and found that after 1.5 years, 65 percent of experimental mice were
still alive, and of those that died, the suspected cause was old age.
Crucially, investigators further found that treated mice did not
develop autoimmune disease, a side effect that could develop if the
vaccine had also targeted PSCA expression in normal cells.

"Theoretically, the vaccine could produce a response in any tissue
that expresses the antigen, but the fact that PSCA is expressed in
such low levels in normal tissue may prevent that complication," he
said.

Still, studies in humans are needed to ensure autoimmunity does not
develop, Kast said.

"We feel this is a very promising approach," he said. "With just two
shots, the vaccine will prime immune cells to be on the lookout for
any cell that over-expresses PSCA."

The study was funded by a pre-doctoral training grant from the
National Institutes of Health and a grant from the Margaret E. Early
Medical Research Trust. USC co-authors include Maria de la Luz Garcia-
Hernandez, Andrew Gray and Otto J. Klinger as well as Bolyn Hubby from
AlphaVax, Inc., of Research Triangle Park, North Carolina.