Immunotherapy for Prostate Cancer: What's the Future?

HLA Class II Antigen Presentation in Prostate Cancer Cells: A Novel Approach to Prostate Tumor Immunotherapy

Prostate cancer is a deadly disease that is in drastic need of new treatment strategies for late stage and metastatic prostate cancer. Immunotherapy has emerged as a viable option to fill this void. Clinical trials have been conducted that induce tumor clearance through cytotoxic T lymphocyte (CTL) activation, these studies have had mixed outcomes with the overlying problem being the lack of a complete immune response with sustained killing and the formation of tumor specific memory cells. To overcome this, we have outlined the need for activating the HLA class II pathway in inducing a sustained CD8+ T cell response and the development of effective memory. We have also discussed the ability of prostate cancer cells to express stable HLA class II molecules that can be manipulated for tumor antigen (Ag) processing and presentation. This review also sets to outline new directions that exist for the use of class II-restricted Ags/peptides in devising cancer vaccines as well as combined chemoimmunotherapy. A better understanding of these concepts will improve future cancer vaccine studies and further the field of cancer immunobiology.

Evolving perspectives of the role of novel agents in androgen-independent prostate cancer

Metastatic androgen-independent prostate cancer presents an intriguing clinical challenge, with a subtle interaction between hormone-responsive and refractory tumor cell elements. The treatment of advanced prostate carcinoma, which had remained stagnant for several decades following the understanding of the link between androgenic stimulation and carcinogenesis, has now started to make steady headway with chemotherapy and targeted approaches. Metastatic prostate cancer is almost always treated with initial androgen deprivation, in various forms. However, despite such treatment androgen-independent prostate cancer cells eventually emerge and progress to threaten life. The therapeutic objectives for treatment of metastatic prostate cancer are to maintain the quality of life and prolong survival. The out-dated nihilistic dogma of deferring chemotherapy until the most advanced stages in advanced prostate cancer is now falling by the wayside with the development of newer effective, tolerable agents.

Therapeutic cancer vaccines

Therapeutic cancer vaccines target the cellular arm of the immune system to initiate a cytotoxic T-lymphocyte response against tumor-associated antigens. Immunotherapy offers one of the few therapeutic options that reproducibly leads to a subset of patients with long-term remissions (seemingly cures) of widely metastatic disease. Therapeutic cancer vaccines tested in clinical trials have included inactivated tumor cells administered in immunological adjuvants or after genetic modification to increase their immunogenicity. Other forms are heat shock protein vaccines and anti-ganglioside antibodies. Tumor-associated antigenic peptides have been fully characterized for some cancers. Finally, strategies to directly expand antitumor T lymphocytes and adoptively transfer them to patients with cancer have been developed and shown to induce objective tumor regressions.