Abstract

BACKGROUND:

Prostate cancer is currently the most commonly diagnosed cancer in men and the second leading cause of cancer-related death in men in the US. Immunological approaches may provide an alternative option for prevention and treatment of prostate cancer.

METHODS:

To develop vaccine against prostate cancer using mouse model, we constructed three recombinant adenoviruses expressing prostate-specific membrane antigen (rAd/PSMA), prostate stem cell antigen (rAd/PSCA) and six-transmembrane epithelial antigen of the prostate (rAd/STEAP), that were specifically up-regulated in the transgenic murine prostate cancer.

RESULTS:

Male C57BL/6 mice were immunized by intravenous injection of these recombinant adenoviruses and subsequently by subcutaneous injection of dendritic cells pulsed with TRAMP-C1 tumor lysate. After subcutaneous challenge with TRAMP-C1 cells, tumor growth was significantly delayed in the immunized mice compared to the control group. Surprisingly, significant numbers of STEAP-specific CD8 T cells were detected in the peripheral blood and the spleen of immune mice using MHC I tetramers, and injection of rAd/STEAP alone followed by pulsed DC was sufficient to inhibit tumor growth. Therapeutic vaccination also significantly delayed the growth of pre-established tumors.

CONCLUSION:

Our results suggest that STEAP is a good immunologic target antigen against prostate cancer and our vaccination regimen successfully elicits anti-tumor CTL responses and suppresses tumor growth. More studies will expedite the development of this vaccine toward clinical application.