title: CpG oligonucleotide as an adjuvant for the treatment of prostate cancer.
abstract: The use of an adenovirus transduced to express a prostate cancer antigen (PSA) as a vaccine for the treatment of prostate cancer has been shown to be active in the destruction of antigen-expressing prostate tumor cells in a pre-clinical model, using Balb/C or PSA transgenic mice. The destruction of PSA-secreting mouse prostate tumors was observed in Ad/PSA immunized mice in a prophylaxis study with 70% of the mice surviving long term tumor free. This successful immunotherapy was not observed in therapeutic studies in which tumors were established before vaccination and the development of anti-PSA immune response was not as easily generated in PSA transgenic mice. Immunization of conventional and transgenic animals was enhanced by incorporating a collagen matrix into the immunizing injection. Therefore the need to strengthen anti-PSA and anti-prostate cancer immunity was an obvious next step in developing a successful prostate cancer immunotherapy. Because the use of immunostimulatory CpG motifs was shown to enhance immune responses to a wide variety of antigens, our studies incorporated CpG into the Ad/PSA vaccine experimental plans. The results of the subsequent studies demonstrated a dichotomy where Ad/PSA plus CpG enhanced the in vivo destruction of PSA-secreting tumors and the survival of experimental animals, but revealed that the number and in vitro activities of antigen specific CD8+ T cells was decreased as compared to the values observed when the vaccine alone was used for immunization. The dichotomous observations were confirmed using another antigen system, OVA also incorporated into a replication defective adenovirus. Despite the reduction in antigen-specific CD8+ cells after vaccine plus CpG immunization the enhanced destruction of sc and systemic tumors was shown to be mediated entirely by CD8+ T cells. Finally, the reduction of the CD8+ T cells was the result of an observed decrease in the proliferation of the antigen specific cell population.
authors.affiliation: Department of Urology, University of Iowa, Iowa City, 52242, United States. david-lubaroff@uiowa.edu
authors.forename: David M
authors.initials: DM
authors.lastname: Lubaroff
authors.forename: Dev
authors.initials: D
authors.lastname: Karan
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D019496:Cancer Vaccines / Q000627:therapeutic use*; D018899:CpG Islands; D007167:Immunotherapy; D008297:Male; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology*; D017430:Prostate-Specific Antigen / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D011471:Prostatic Neoplasms / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects / Q000276:immunology
chemical_list: D000276:Adjuvants, Immunologic; C408982:CPG-oligonucleotide; D019496:Cancer Vaccines; D009838:Oligodeoxyribonucleotides; D017430:Prostate-Specific Antigen