Therapeutic Vaccines for Prostate Cancer

Designing an Epitope-Based Peptide Vaccine Derived from RNA-Dependent RNA Polymerase (RdRp) against Dengue Virus Serotype 2

Dengue fever (DF) continues to be one of the tropical and subtropical health concerns. Its prevalence tends to increase in some places in these regions. This disease is caused by the dengue virus (DENV), which is transmitted through the mosquitoes Aedes aegypti and A. albopictus. The treatment of DF to date is only supportive and there is no definitive vaccine to prevent this disease. The non-structural DENV protein, RNA-dependent RNA Polymerase (RdRp), is involved in viral replication. The RdRp-derived peptides can be used in the construction of a universal dengue vaccine. These peptides can be utilized as epitopes to induce immunity. This study was an in silico evaluation of the affinity of the potential epitope for the universal dengue vaccine to dendritic cells and the bonds between the epitope and the dendritic cell receptor. The peptide sequence MGKREKKLGEFGKAKG generated from dengue virus subtype 2 (DENV-2) RdRp was antigenic, did not produce allergies, was non-toxic, and had no homology with the human genome. The potential epitope-based vaccine MGKREKKLGEFGKAKG binds stably to dendritic cell receptors with a binding free energy of −474,4 kcal/mol. This epitope is anticipated to induce an immunological response and has the potential to serve as a universal dengue virus vaccine candidate.

Immunotherapeutics for the treatment of prostate cancer: a patent landscape based on key therapeutic mechanisms of actions

The area of immunotherapeutics for the treatment of metastatic castrate-resistant prostate cancer has made significant progress since the autologous cell-based vaccine sipuleucel T became the first and to date only immunotherapy for its treatment. This review focuses on a broad patent landscaping exercise of this therapeutic area and considers if basing this landscaping on key mechanisms of action is appropriate to elicit the main patenting trends.

Expression of a Human Prostatic Acid Phosphatase (PAP)-IgM Fc Fusion Protein in Plants Using In vitro Tissue Subculture

In this study, prostatic acid phosphatase (PAP), which is overexpressed in human prostate cancer cells, was cloned to be fused to the IgM constant fragment (Fc) for enhancing immunogenicity and expressed in transgenic tobacco plants. Then, the transgenic plants were propagated by in vitro tissue subculture. Gene insertion and expression of the recombinant PAP-IgM Fc fusion protein were confirmed in each tested the first, second, and third subculture generations (SG₁, SG₂, and SG₃, respectively). Transcription levels were constantly maintained in the SG_1, SG₂, and SG₃ leaf section (top, middle, and base). The presence of the PAP-IgM Fc gene was also confirmed in each leaf section in all tested subculture generations. RNA expression was confirmed in all subculture generations using real-time PCR and quantitative real-time PCR. PAP-IgM Fc protein expression was confirmed in all leaves of the SG₁, SG₂, and SG₃ recombinant transgenic plants by using quantitative western blotting and chemiluminescence immunoassays. These results demonstrate that the recombinant protein was stably expressed for several generations of in vitro subculture. Therefore, transgenic plants can be propagated using in vitro tissue subculture for the production of recombinant proteins.

Therapeutic vaccines as a promising treatment modality against prostate cancer: rationale and recent advances

Cancer immunotherapy was deemed the medical breakthrough of 2013, in part because it can induce a rapid, durable, self-propagating and adaptable immune response. Specifically in prostate cancer, immunotherapy has emerged as a viable and attractive treatment strategy. To date, therapeutic cancer vaccines and immune checkpoint inhibitors are the two classes of immunotherapy that have demonstrated improvements in overall survival in patients with advanced tumors. The 2010 Food and Drug Administration approval of sipuleucel-T for asymptomatic or minimally symptomatic metastatic prostate cancer set the stage for ongoing phase III trials with the cancer vaccine PSA-TRICOM and the immune checkpoint inhibitor ipilimumab. A class effect of these approved immune-based therapies is a benefit in overall survival without short-term changes in disease progression, apparently due to modulation of tumor growth rate kinetics, in which the activated immune system exerts constant immunologic pressure that slows net tumor growth. A growing body of evidence suggests that the ideal population for clinical trials of cancer vaccines as monotherapy is patients with lower tumor volume and less aggressive disease. Combination strategies include immunotherapy with standard therapies or with other immunotherapies. Here we review emerging data on immunotherapy for patients with prostate cancer.

A prospective study of the efficacy of a combination of autologous dendritic cells, cytokine-induced killer cells, and chemotherapy in advanced non-small cell lung cancer patients

Dendritic cells (DC) play a crucial role in the induction of an effective antitumor immune response. Cytokine-induced killer (CIK) cells, a subset of T lymphocytes, have the capacity to eliminate cancer cells. This study was to evaluate the correlation between the frequency of DC/CIK immunotherapies following regular chemotherapy, the time-to-progression (TTP), and overall survival (OS) of advanced non-small lung cancer patients. Sixty patients with IIIB-IV non-small-cell lung carcinoma (NSCLC) were enrolled from August 2007 to December 2009 and were randomized into two groups. All 60 patients received four courses of navelbine-platinum (NP) chemotherapy. In one group, 30 patients were treated with adoptive autologous DC/CIK cell transfusion twice every 30 days. In the other group, the patients received immunotherapies more than twice every 30 days. The adverse effects, TTP, and OS were evaluated between the two groups. Median survival time of all 60 patients was 13.80 months. The 1-, 2-, and 3-year overall survival rates were 60.0, 21.7, and 15.0 %, respectively. The 1-, 2-, and 3-year overall survival rates of patients receiving more than two immunotherapies were 63.3, 30.0, and 23.3 %, and the rates of those receiving two immunotherapies were 56.7, 13.3, and 6.7 %, respectively. The difference between the two groups was statistically significant (P = 0.037). Compared with patients in the fewer immunotherapies group, TTP in the group receiving more immunotherapies significantly prolonged, with the median improving from 6.2 months (95 % CI, 5.35-9.24) to 7.3 months (95 % CI, 5.45-6.95; P = 0.034). The adverse effects of chemoimmunotherapy were tolerable. Advanced NSCLC patients can benefit from the combination of DC/CIK immunotherapies following conventional chemotherapy. More than two immunotherapies improved TTP and OS of those patients in this study.

Generation of potent cytotoxic T lymphocytes against castration-resistant prostate cancer cells by dendritic cells loaded with dying allogeneic prostate cancer cells

To induce a potent cytotoxic T lymphocyte (CTL) response in dendritic cell (DC)-based immunotherapy against prostate cancer, various tumour antigens should be loaded onto DCs. The aim of this study was to establish a method of immunotherapy for castration-resistant prostate cancer (CRPC) using prostate cancer-specific CTLs generated in vitro by DCs. Monocyte-derived DCs from patients with CRPC were induced to mature using a standard cytokine cocktail (in IL-1β, TNF-α, IL-6 and PGE(2) : standard DCs, sDCs) or using an α-type 1-polarized DC (αDC1) cocktail (in IL-1β, TNF-α, IFN-α, IFN-γ and polyinosinic:polycytidylic acid) and loaded with the UVB-irradiated CRPC cell line PC-3. Antigen-loaded DCs were evaluated by morphological and functional assays. The αDC1s significantly increased the expression of several molecules related to DC maturation, regardless of whether the αDC1s were loaded with tumour antigens or not, compared to sDCs. The αDC1s showed a higher production of interleukin-12 both during maturation and after subsequent stimulation with CD40L, which was not significantly affected by loading with tumour antigens, as compared to standard DCs (sDCs). Prostate cancer-specific CTLs against autologous CRPC cells were successfully induced by αDC1s loaded with dying PC-3 cells. Autologous αDC1s loaded with an allogeneic CRPC cell line can generate greater CRPC-specific CTL responses as compared to sDCs and may provide a novel source of DC-based vaccines that can be used for the development of immunotherapy in patients with CRPC.

Concise review: cell therapies: the route to widespread adoption

We identify three dimensions with which to classify heuristically the routes to widespread adoption of cellular therapies. The first dimension is based on the relative involvement of clinicians and companies in a particular cellular therapy. The second dimension is based on cell type and consequent scale of manufacture. The third dimension classifies the therapeutic intervention as a procedure or product and has perhaps received less attention. We suggest that for those cellular therapies that require therapeutic procedures, close collaboration between companies and clinicians will reduce the time to widespread adoption. For selected cellular therapies we make predictions of the likely time to widespread adoption.

Horizon scanning for novel therapeutics for the treatment of prostate cancer

Treatment options for patients with advanced prostate cancer (PCa) remain limited. Improved understanding of the underlying molecular drivers of PCa pathogenesis, progression and resistance development has provided the fundamental basis for rational targeted drug design. Key findings in recent years include the identification of ETS gene rearrangements, the dissection of PCa molecular heterogeneity and the discovery that castration-resistant prostate cancer (CRPC) remains androgen driven despite the androgen-depleted milieu, thus making androgen receptor (AR) signaling a continued focus of molecularly targeted treatments. AR ligand-independent activation of tyrosine kinase prosurvival signaling cascades and angiogenesis have also been implicated in disease progression. A multitude of new molecularly targeted agents that abrogate AR signaling, inhibit the mitogenic and prosurvival signal transduction pathways, perturb the tumor-bone microenvironment, impair tumor vasculature, facilitate immune modulation and induce apoptosis are in clinical development and are highly likely to change the current treatment paradigm. It is clear that the success of these molecular targeted therapies hinges in part on optimal patient selection based on the molecular disease profile and an improved understanding of the mechanistic basis of acquired resistance. This review outlines the current clinical development of molecular targeted treatments in CRPC, with particular emphasis on agents that are in the later stages of clinical development, and details the challenges and future direction of developing these antitumor agents.

Strategies for prostate cancer prevention: Review of the literature

The goal of primary chemoprevention is to decrease the incidence of a given cancer, simultaneously reducing treatment-related adverse events, cost of treatment of the disease and mortality. Prostate cancer is an attractive and appropriate target for primary prevention because of its high incidence and prevalence, increased disease-related mortality, long latency and molecular pathogenesis and epidemiological data indicating that modifiable environmental factors may decrease risk. Various agents have been suggested to prevent prostate cancer and many clinical trials are currently on. Ultimately the adoption of a preventive strategy hinges on its potential benefits weighed against the potential risks of the specific agents used. This article is aimed to examine the experimental and epidemiological data spanning a period of 1998 to 2007, demonstrating the chemopreventive activity, safety and toxicity of various nutritional elements and other agents that can help prevent prostate cancer and/or slow disease progression.

Adoptive cell therapy of prostate cancer using female mice-derived T cells that react with prostate antigens

In this study, we report a novel treatment strategy that could potentially be used to improve efficacy of adoptive cell therapy for patients with prostate cancer. We show that female C57BL/6 mice are able to effectively reject two syngeneic prostate tumors (TRAMP-C2 and RM1) in a T cell-dependent manner. The protective antitumor immunity appears to primarily involve T cell responses reactive against general prostate tumor/tissue antigens, rather than simply to male-specific H-Y antigen. For the first time we show that adoptive transfer of lymphocytes from TRAMP-C2-primed or naïve female mice effectively control prostate tumor growth in male mice, when combined with host pre-conditioning (i.e., non-myeloablative lymphodepletion) and IL-2 administration. No pathological autoimmune response was observed in the treated tumor-bearing male mice. Our studies provide new insights regarding the immune-mediated recognition of male-specific tissue, such as the prostate, and may offer new immunotherapy treatment strategies for advanced prostate cancer.

Horizon scanning for novel therapeutics for the treatment of prostate cancer

IMPORTANCE OF THE FIELD

Treatment options for patients with advanced prostate cancer (PCa) remain limited. Improved understanding of the underlying molecular drivers of prostate cancer pathogenesis, progression and resistance development has provided the fundamental basis for rational targeted drug design.

AREAS COVERED IN THIS REVIEW

This review will discuss the most recent developments in the field of prostate cancer therapies including key findings such as the identification of ETS gene rearrangements, the dissection of prostate cancer molecular heterogeneity and the discovery that castration-resistant prostate cancer (CRPC) remains androgen-driven despite the androgen-depleted milieu, thus making androgen receptor signaling a continued focus of molecularly targeted treatments. A multitude of new molecularly targeted agents are in clinical development and are highly likely to change the current treatment paradigm.

WHAT THE READER WILL GAIN

This review will outline the current clinical development of molecular targeted treatments in CRPC.

TAKE HOME MESSAGE

Unraveling the complex molecular biology that underpins this heterogeneous disease may pave the way to personalized therapy with a wide range of rationally targeted agents and combination treatments. In conclusion, we can predict that the rational clinical development of new targeted drugs will improve the outcome of men with prostate cancer in the years ahead.

The choice of the antigen in the dendritic cell-based vaccine therapy for prostate cancer

Tumor antigens (TA) are promising candidates for targeted treatment of prostate cancer (PCa). Critical issues in the preparation of dendritic cell (DC)-based TA vaccines are the DC maturation state and the appropriateness of the TA. Prostate-specific antigen (PSA) and prostate acide pshosphatase (PAP) presented by DC have produced encouraging results and PAP-loaded DCs are at late-stage development for PCa patients. TAs indispensable for tumor survival and propagation are now emerging as first choice TAs for future vaccines. The increased expression and enzymatic activity of prostate specific membrane antigen (PSMA) and prostate stem cell antigen (PSCA) by aggressive prostate tumors is indicative of a unique, selective advantage on the part of cells expressing them. Human telomerase reverse transcriptase (hTERT) and survivin are both involved in tumor cell survival and considered universal TAs. The T cell epitope potential of peptides derived from these TAs has been defined by computer-assisted prediction programs and has been tested in vitro and in vivo in terms of their ability to recruit cytotoxic T lymphocytes (CTL) and to be recognised as CTL targets. Results, reviewed here, show that anti-tumor immunity can be induced in vivo by DC loaded with both whole TAs and TA peptides. The promising, but still limited clinical success suggests further exploration of this immune therapy in the more appropriate setting of minimal disease. In advanced stages, vaccine can still be effective when combined with systemic or local cytoreductive therapies, which may overcome antigen specific tolerance and subvert the tumor immunosuppressive environment.

Tumor-Associated Antigens and Biomarkers in Cancer and Immune Therapy

Cancer has currently overtaken heart disease as the major cause of mortality in the United States. The Human Genome Project, advances in informatics, miniaturization of sample collection, and increased knowledge of cell signaling pathways has revolutionized the study of disease. Genomics, proteomics, and metabolomics are currently being used to develop molecular signatures for disease diagnosis, prognosis, and therapeutic efficacy. Tumor-associated antigens discovered by these methods are being used to develop passive (humoral) as well as active immunotherapy strategies to stimulate the immune system. Development and validation of biomarkers on a parallel track with therapeutics can speed development times by accurate screening of patient populations and substituting surrogate markers that correlate well with clinical outcomes.

Cyclophosphamide augments antitumor immunity: studies in an autochthonous prostate cancer model

To study the immune response to prostate cancer, we developed an autochthonous animal model based on the transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse in which spontaneously developing tumors express influenza hemagglutinin as a unique, tumor-associated antigen. Our prior studies in these animals showed immunologic tolerance to hemagglutinin, mirroring the clinical situation in patients with cancer who are generally nonresponsive to their disease. We used this physiologically relevant animal model to assess the immunomodulatory effects of cyclophosphamide when administered in combination with an allogeneic, cell-based granulocyte-macrophage colony-stimulating factor-secreting cancer immunotherapy. Through adoptive transfer of prostate/prostate cancer-specific CD8 T cells as well as through studies of the endogenous T-cell repertoire, we found that cyclophosphamide induced a marked augmentation of the antitumor immune response. This effect was strongly dependent on both the dose and the timing of cyclophosphamide administration. Mechanistic studies showed that immune augmentation by cyclophosphamide was associated with a transient depletion of regulatory T cells in the tumor draining lymph nodes but not in the peripheral circulation. Interestingly, we also noted effects on dendritic cell phenotype; low-dose cyclophosphamide was associated with increased expression of dendritic cell maturation markers. Taken together, these data clarify the dose, timing, and mechanism of action by which immunomodulatory cyclophosphamide can be translated to a clinical setting in a combinatorial cancer treatment strategy.

Dominance of CD4+ lymphocytic infiltrates with disturbed effector cell characteristics in the tumor microenvironment of prostate carcinoma

BACKGROUND

Prostate cancer is the most common cancer of men in the Western world. Despite the over-expression of tumor-associated antigens, like PSA or PSMA, immune activation is inefficient. The goal of this investigation was to assess in situ characteristics of prostate cancer-infiltrating lymphocytes and to determine their activation status and effector function.

METHODS

We compared 17 carcinoma containing tissues, four benign prostatic hyperplasia tissues and eight healthy prostate tissues regarding lymphocyte subset composition, locoregional distribution, and functional status using immunohistological staining of cryopreserved tissues. For determination of lymphocyte subsets, serial sections were stained with CD3, CD4, and CD8 antibodies. Activation status and effector function were studied using CD69, interferon-gamma (IFN gamma), perforin, and CD3 zeta chain antibodies. T-cell-receptor repertoire (TCR) analysis was made to determine the complexity of infiltrating lymphocytes.

RESULTS

CD3+, CD4+, and CD69+ T lymphocytes were prominent in tissues derived from patients with prostate carcinoma. CD8+ lymphocytes were significantly less than CD4+ lymphocytes. IFN gamma and perforin were downregulated on infiltrating lymphocytes compared to cells of healthy prostate tissue. Very few lymphocytes were detected within cancerous lesions whereas surrounding tissues showed extensive lymphocyte cluster formation. The TCR repertoire of infiltrating lymphocytes was broad and similar to that of healthy prostate tissue, giving no evidence for specific lymphocyte recruitment.

CONCLUSIONS

In the prostate cancer microenvironment, CD4+ T lymphocytes dominated while CD8+ T cells were sparse. The lymphocytes exhibited signs of disturbed effector function. Consequently, the immune response against autologous tumor cells is likely to be inefficient in controlling tumor growth.

Clinical safety of a viral vector based prostate cancer vaccine strategy

PURPOSE

The primary objective of this phase I study was to evaluate the clinical safety of a vaccine using recombinant vaccinia virus (prime) and recombinant fowlpox virus (boost) in combination with granulocyte-macrophage colony-stimulating factor in patients with prostate cancer. The vaccines contained transgenes for prostate specific antigen, a triad of co-stimulatory molecules and a tumor antigen whose amino acid sequence had been modified to enhance its immunogenicity. Secondary end points were immunological and clinical responses, changes in prostate specific antigen velocity, and the kinetics of vaccinia virus clearance from the vaccination site, serum, peripheral blood mononuclear cells, urine and saliva.

MATERIALS AND METHODS

The 15 patients enrolled in this study had metastatic prostate cancer. Patients were given recombinant fowlpox-prostate specific antigen/triad of co-stimulatory molecules alone or recombinant vaccinia-prostate specific antigen/triad of co-stimulatory molecules followed by recombinant fowlpox-prostate specific antigen/triad of co-stimulatory molecules on a prime and boost schedule with or without recombinant-granulocyte-macrophage colony-stimulating factor protein or recombinant fowlpox-granulocyte-macrophage colony-stimulating factor vector. Prostate specific antigen specific immune responses were measured using an enzyme-linked immunosorbent spot assay for interferon-gamma production. Polymerase chain reaction for vaccinia DNA and a plaque assay for live virus were also used.

RESULTS

Some grade 2 toxicity was seen in patients who received a higher dose of recombinant fowlpox-granulocyte-macrophage colony-stimulating factor but no toxicity exceeded grade 2. Viable vaccinia was detected after vaccination at the site swab of 1 of 4 patients analyzed. Prostate specific antigen specific immune responses were seen in 4 of 6 patients who were HLA-A2+ and decreases in serum prostate specific antigen velocity were observed in 9 of 15.

CONCLUSIONS

Based on the safety and preliminary immunogenicity results of this trial we recommend initiating a randomized, phase II study of prostate specific antigen/triad of co-stimulatory molecules vaccines in patients with less advanced prostate cancer.

Prevention of human PC-346C prostate cancer growth in mice by a xenogeneic tissue vaccine

Vaccination, as an approach to prostate cancer, has largely focused on immunotherapy utilizing specific molecules or allogeneic cells. Such methods are limited by the focused antigenic menu presented to the immune system and by immunotolerance to antigens recognized as "self". To examine if a xenogeneic tissue vaccine could stimulate protective immunity in a human prostate cancer cell line, a vaccine was produced by glutaraldehyde fixation of harvested PAIII prostate cancer cells tumors (GFT cell vaccine) from Lobund-Wistar rats. Immunocompetent Ncr-Foxn1 mice were vaccinated with the GFT cell vaccine four times, 7 days apart. The control animals were either not vaccinated or vaccinated with media or glutaraldehyde-fixed PC346C human prostate cancer cells and adjuvant. About 8 days after the final boost, serum and spleens were harvested. The splenocytes were co-incubated with PC346C cells and then transplanted orthotopically into sygneneic immunodeficient nude mice. About 10 weeks later, the prostates were weighed and sampled for histolologic examination. The spleens were harvested from additional mice, and the splenocytes were cultured, either with or without pulsing by GFT cells, and the supernatants harvested 72 h later for cytokine analysis. Results showed that vaccination with GFT cells resulted in increased serum antibody to a PAIII cell lysate; reduced weight of the prostate/seminal vesicle complex and reduced incidence of prostate cancer in nude mice; increased splenocyte supernatant levels of TNF-alpha, IL-2, IFN-gamma and IL-12, cytokines associated with Th1 immunity; and increased splenocyte supernatant levels of IL-4 and IL-10, cytokines associated with Th2 immunity. In summary, the results suggest that use of a xenogeneic tissue vaccine can stimulate protective immunity against human prostate cancer cells.

Vaccines: an innovative approach to treating cancer

Recent scientific advances have expanded our understanding of the immune system and its response to malignant cells. Clinical trials are under way that attempt to translate this knowledge into effective cancer therapies. Vaccine therapy, an innovative approach to cancer treatment, attempts to activate the immune system to recognize cancer cells and eliminate them from the body. Preventive vaccines that already have been approved will have an impact on the incidence of certain cancers, and research is ongoing into treatment vaccines for various cancers.

Increased expression of anterior gradient-2 is significantly associated with poor survival of prostate cancer patients

Anterior gradient-2 (AGR2) expression was examined in a series of prostate cell lines and in an archival set of prostate tissues. The relative levels of AGR2 expression in the malignant cell lines PC-3 and PC-3M were, respectively, 5.3+/-0.1 and 3.8+/-0.2 times that detected in the benign cell line PNT-2. Immunohistochemical staining in 106 cases showed that amongst seven normal cases, one (14.3%) was unstained, five (71.4%) stained weakly positive and one (14.3%) stained moderately positive. Amongst 34 benign prostate hyperplastic (BPH) cases, 12 (35.3%) were unstained, 18 (52.9%) stained weakly positive and four (11.8%) stained moderately positive. Amongst 65 carcinomas, three (4.6%) were unstained, 14 (21.5%) stained weakly positive, 19 (29.2%) stained moderately positive and 29 (44.9%) stained strongly positive. AGR2 expression in carcinomas was significantly higher than that in BPH (chi(2)-test, P<0.001). Kaplan-Meier survival analysis showed that increased AGR2 expression was significantly (log rank test, P=0.007) associated with reduced patient-survival time. Increased joint Gleason score (GS) was significantly (log rank test, P=0.001) associated with poor patient survival. However, neither prostate specific antigen (PSA) level, nor androgen receptor (AR) index, was significantly associated with patient-survival time. Increased AGR2 expression was significantly correlated with high GS (two-sided Fisher's exact test, P<0.001) and PSA levels (Mann-Whitney U-test, P=0.047), but not significantly related to the level of AR (Mann-Whitney U-test, P=0.286). These results suggest that increased AGR2 expression is a valuable prognostic factor to predict the clinical outcome of the prostate cancer patients.

Advances in preclinical investigation of prostate cancer gene therapy

Treating recurrent prostate cancer poses a great challenge to clinicians. Research efforts in the last decade have shown that adenoviral vector-based gene therapy is a promising approach that could expand the arsenal against prostate cancer. This maturing field is at the stage of being able to translate many preclinical discoveries into clinical practices. At this juncture, it is important to highlight the promising strategies including prostate-targeted gene expression, the use of oncolytic vectors, therapy coupled to reporter gene imaging, and combined treatment modalities. In fact, the early stages of clinical investigation employing combined, multimodal gene therapy focused on loco-regional tumor eradication and showed promising results. Clinicians and scientists should seize the momentum of progress to push forward to improve the therapeutic outcome for the patients.

Potent systemic antitumor immunity induced by vaccination with chemotactic-prostate tumor associated antigen gene-modified tumor cell and blockade of B7-H1

We previously reported that several DNA fragments from human prostate-specific membrane antigen (hPSM), mouse prostatic acid phosphatase (mPAP), and human prostate-specific antigen (hPSA) genes were selected and fused to create a novel hPSM-mPAP-hPSA fusion gene (named 3P gene), and human secondary lymphoid tissue chemokine (SLC), 3P, and human IgG Fc genes were inserted into pcDNA3.1 to construct a DNA vaccine, designated pSLC-3P-Fc. In this report, to establish a more efficient treatment for immunotherapy against prostate cancer, the construct was transfected into B16F10 to generate gene-modified tumor cell vaccine (named B16F10-SLC-3P-Fc). In poorly immunogenic B16F10 mouse melanoma model, the immunization with B16F10-SLC-3P-Fc resulted in a strong antitumor response and 50% of tumor-bearing mice achieved long-term survival (>120 days). In vivo depletion of lymphocytes indicated that CD8(+) T cells were involved in the direct tumor killing, whereas CD4(+) T lymphocytes were required for the induction of CD8(+) CTL response in B16F10-SLC-3P-Fc-immunized mice. Splenocytes from B16F10-SLC-3P-Fc-immunized mice specifically recognized and lysed PSM, PAP, PSA, and 3P expressing tumor cells. The combined therapy of B16F10-SLC-3P-Fc plus anti-B7-H1 MAbs further enhanced the immune response. Rechallenge experiment showed that a persistent memory response was successfully induced by the combined therapy. These observations suggest pSLC-3P-Fc-modified tumor cells could serve as a vaccine against prostate cancer, and the therapy combined with anti-B7-H1 MAbs further enhanced the antitumor immune response.