The goal of the current project is to develop methods to induce the immune system of a patient with prostate cancer to destroy his tumor. The prostate gland selectively expresses a number of proteins that are typically expressed on malignant prostate cancer cells. Theoretically, small segments of these proteins are excised and presented on the surface of the tumor cell in association with immune presentation molecules known as class I HLA molecules. We hypothesize that killer immune cells known as T lymphocytes can be activated to specifically recognize the combined complex of a class I HLA molecule and a prostate protein fragment on the surface of a tumor cell. T lymphocytes are able to circulate throughout the body and therefore might be able to seek out and destroy tumor cells in a highly specific fashion. Normal prostate cells also might be destroyed by such cells. However, the prostate gland is not essential for survival and is often removed as part of conventional therapy. In this circumstance, prostate-specific immune T cells should only destroy prostate cancer cells. The specific objective of the current project is to identify prostate protein fragments that can selectively target the killing of prostate cancer cells. It is also our goal to show that T cells capable of recognizing prostatic protein fragments can be activated from the blood of patients with prostate cancer. Some patients may not be able to generate specific T cell responses; however, it may be possible to engineer patients¿ T lymphocytes to become effector killer cells by introducing specific T lymphocyte receptors from normal donors into patients¿ lymphocytes by gene transfer techniques. The project will focus on identifying immunogenic peptide fragments of two well-characterized proteins that are expressed by most prostate cancers, prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSM). These proteins are reciprocally expressed by the majority of tumors. Therefore, combined immune responses to both proteins may have additive or synergistic therapeutic effects. There are many different class I HLA molecules in the human population; however, a limited number of specific class I molecules are expressed with disproportionately high frequencies. Our studies will focus on finding PSA and PSM peptide fragments that bind to the most common class I HLA determinants found in the general population and in subpopulations at particularly high risk for the development of prostate cancer, i.e., African Americans. Computerized algorithms will be used to identify peptide segments of PSA and PSM that potentially can bind to particular class I HLA molecules. These peptides will be synthesized and tested for their ability to induce killer T cells from blood cells of healthy individuals. The T cells will be grown in culture plates and tested for the ability to kill tumor cells that express the corresponding prostatic protein. Prostatic peptides that activate T cells that kill tumor cells will then be studied for their ability to induce killer T cells from the blood of patients with prostate cancer. T cells that are especially effective at killing tumor cells will be used to isolate the genes that encode the receptors that direct the killing of tumor cells. The T cell receptor genes will be introduced into naive lymphocytes to determine whether the cells can be ¿taught¿ to recognize and lyse tumor cells. Eventually, it might be possible to routinely engineer patients¿ lymphocytes with appropriately selected receptors that have been recovered from other individuals of the same HLA type. Alternatively, it might be possible to directly vaccinate patients to respond to the prostatic target peptides in order to treat their tumors. We are currently testing the ability of a PSA peptide that fulfills the criteria described above to vaccinate patients with prostate cancer. Prostatic target peptides that are identified by the current project should enable this approach to be extended to a majority of individuals affected by prostate cancer.