Vaccine prevents prostate cancer development in mice

Researchers at the University of Southern California, Los Angeles, have developed a prostate cancer vaccine that prevented the development of cancer in 90% of young mice genetically predestined to develop the disease, and suggest the same strategy might work for men with rising levels of PSA (Cancer Res 2008; 68:861-9).

“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, PhD, of the Norris Comprehensive Cancer Center at USC. “This has never been done before, and, with further research, could represent a paradigm shift in the management of human prostate cancer.”

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 delivered a fragment of DNA that coded for prostate stem cell antigen (PSCA), thus producing an influx of PSCA protein to alert the immune system. The booster shot, given 2 weeks later, used a modified horse virus to deliver the PSCA gene.

In the experimental group, two of 20 mice developed prostate cancer at the end of 1 year, while 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,” Dr. Kast said. “The vaccination turned the cancer into a chronic, manageable disease.”