Anti-prostate specific membrane antigen designer T cells for prostate cancer therapy

BACKGROUND: Designer T cells are T lymphocytes engineered toward specific antibody-type membrane antigens through chimeric immunoglobulin-T-cell receptor (IgTCR) genes that have been used for adoptive cellular immunotherapy. We have extended this approach to prostate specific membrane antigen (PSMA) as a means to attack prostate cancer. METHODS: A chimeric anti-PSMA IgTCR gene was constructed based on an anti-PSMA monoclonal antibody, 3D8. Both T-cell lines and primary cultured human T lymphocytes were transduced with the chimeric anti-PSMA IgTCR construct and were analyzed for IgTCR expression, specific activation by PSMA, cytotoxicity against PSMA-expressing tumor cells in vitro, and retardation of tumor growth in an animal model. RESULTS: The IgTCR was incorporated into the TCR-CD3 complex and formed a functional chimeric complex. The IgTCR-modified T cells were specifically activated through the chimeric receptor with PSMA as measured by IL-2 production and increased CD25 expression and specifically lysed the PSMA-expressing prostate cancer cells in vitro as well as retarded tumor growth in an animal model. CONCLUSIONS: The anti-PSMA designer T cells exhibit an antibody-type specificity that can recognize PSMA expressing tumor cells in a MHC-independent fashion, resulting in T-cell activation, target cell lysis in vitro and inhibition of tumor growth in vivo.     

PSMA expression in Schwannoma: a potential clinical mimicker of metastatic prostate carcinoma

ObjectivesRadioimmunoscintigraphy using a radiolabeled antibody against prostate-specific membrane antigen (PSMA) is frequently used to detect prostate carcinoma (PCa) recurrence and metastasis to lymph nodes, soft tissues, and bone. PSMA expression has been shown in occasional nonprostatic neoplasms (e.g., urothelial adenocarcinoma) and in the vasculatures of other malignancies. PSMA expression has not been described in benign neoplasms. Recently, during evaluation of a prostatic carcinoma patient, we encountered a false positive PSMA radioimmunoscintigraphy scan in a pathologically confirmed Schwannoma (SCH) lesion. The current study further evaluates PSMA expression in Schwannomas.MethodsEleven SCH were retrieved from our surgical pathology archives. Representative sections were immunostained with monoclonal antibody for PSMA. PSMA expression was evaluated in tumor cells and lesional vessels. Extent of staining was calculated as percent of positive cells in highest areas of expression. Positive staining was considered focal, multifocal, or diffuse based on the percent of positive cells: <5%, 5% to 75%, and >75%, respectively.ResultsAll 11 SCH showed tumoral and or vascular staining; 7 (7/11) displayed both vascular and tumoral cell staining; the remaining 4 had only vascular staining (2/11) or tumor cell staining (2/11). The extent of tumoral cell and vascular staining varied widely among lesions (tumor cells: focal in 8 and diffuse in 1; vascular: focal in 7, multifocal in 1, and diffuse in 1 lesion).ConclusionThis is the first report of PSMA expression in a benign neoplasm. Given our finding of frequent expression of PSMA in Schwannomas, they should be clinically considered in the differential diagnosis of a lesion that is positive on PSMA radioimmunoscintigraphy study performed during a metastatic work-up of PCa patient.     

重组腺病毒介导白细胞介素-18和甲胎蛋白基因修饰的树突状细胞体外诱导抗肝癌免疫活性的研究

目的 探讨甲胎蛋白(AFP)、白细胞介素(IL)-18基冈修饰树突状细胞(DC)较以往AFP基因修饰DC作为肝癌免疫治疗瘤苗是否更具优势.方法 分离外周血单个核细胞定向诱导为DC,以Ad-IL-18和Ad-AFP共感染DC,感染后细胞通过噻唑蓝(MTT)比色法检测其激活的T细胞对HepG2的杀伤活性.结果 检测结果显示目的 基因能够表达于DC细胞中.流氏细胞仪(FCM)结果显示共感染的DC细胞均高表达CD1a(73.4%)、CD11c(84.3%)、CD80(89.5%)、CD86(87.9%)和HLA-DR(91.7%).CTL结果显示IL-18/AFP-DC-T对HepG2的杀伤率(67.49±3.24)%明显高于对SMMC7721细胞(27.32±1.75)%和K562细胞(17.31±1.56)%的杀伤率,另外共感染IL-18/AFP-DC-T组对HepG2的杀伤率与AFP-DC-T、IL-18-DC-T组比较,其差异有统计学意义.结论 AFP和IL-18基因修饰DC,能够在体外诱导特异性细胞毒性T淋巴细胞(CTL)效应,而_且对HepG2细胞杀伤率大于AFP转染DC组.     

Telomerase pulsed dendritic cells for immunotherapy for renal cell carcinoma

PURPOSE: Renal cell carcinoma (RCC) is known for its immunological susceptibility. Unfortunately RCC lacks specific tumor antigens for the induction of specific immunotherapy. We investigated the role of telomerase as a tumor antigen and pulsed dendritic cells (DCs) as antigen presenting cells with an immunogenic peptide from telomerase. MATERIAL AND METHODS: DCs and immunological effector cells, that is cytokine induced killer (CIK) cells, from patients with RCC or healthy donors were generated. CIK cells were co-cultured with telomerase peptide pulsed DCs. CIK cells were tested for cytotoxic activity against primary cultures. Using the dimer technique we determined the percent of telomerase specific T cells. Activation status was identified using interferon-gamma secretion assay. RESULTS: After pulsing DCs with telomerase peptide co-cultured CIK cells had a significant increase in cytotoxic activity against tumor cells compared with CIK cells without co-culture, that is 100% at an effector-to-target ratio of 60:1 vs 41.7% (p <0.05). Using a complete autologous model with immunological cells derived from patients with metastatic RCC we were able to induce cytotoxicity against autologous, telomerase positive primary cell cultures. We could detect 2.4% telomerase specific effector cells after co-culture with peptide pulsed DCs, which secreted interferon-gamma after re-stimulation. CONCLUSIONS: Telomerase could serve as a specific tumor associated antigen for RCC. The presentation of telomerase peptide by DCs to lymphocytes allows the generation of antigen specific cytotoxic effector cells.     

In vitro propagated dendritic cells from prostate cancer patients as a component of prostate cancer immunotherapy

T cell-mediated cancer immunotherapy requires efficient antigen-presenting cells. Dendritic cells (DCs) are arguably the most efficient antigen-presenting cells studied to date. Individuals with prostate cancer often undergo various therapies which may compromise their immune system, including the state of their DC precursors. We report the in vitro propagation of DCs from peripheral blood of patients with prostate cancer, most of whom are in clinical stages D₁ or D₂ and have undergone radiation therapy. After 7 days in culture, the number of DCs recovered were 20-50-fold higher than those isolated directly from peripheral blood. This number is comparable to findings of previous studies with healthy individuals. Cultured patients' DCs were capable of presenting tetanus toxoid to autologous T cells in vitro. Furthermore, T cells from 2 of 4 patients proliferated when cultured with their DCs and the lysate of a human prostate cancer cell line (LNCaP), demonstrating the potential role of autologous DCs in prostate cancer immunotherapy studies. © 1995 Wiley-Liss, Inc.     

Mature CD83+ dendritic cells infected with recombinant gp 100 vaccinia virus stimulate potent antimelanoma T cells

Background Mature dendritics cells (DCs) are potent antigen-presenting cells that activate naive T lymphocytes and initiate cellular immune responses. The ability of CD83⁺ mature DCs infected with vaccinia virus encoding the gp 100 melanoma transgene (rV-gp 100) to stimulate an antimelanoma CD8⁺ T-cell response was investigated. Methods Monocyte-derived immature or CD83⁺ mature DCs were infected with rV-gp100. The activation state of the DCs and the expression of gp 100 protein were evaluated by flow cytometry. The reactivity of antimelanoma CD8⁺ T cells was confirmed by measuring specific interferon γ secretion by using enzyme-linked immunosorbent assay in a mixed-tumor lymphocyte culture. Results Both immature and CD83⁺ mature DCs expressed gp 100 protein when the DCs were infected with rV-gp 100. Calcium-signaling agents were required to induce maturation of both infected and nonifected immature DCs. Only rV-gp100-infected CD83⁺ DCs induced CD8⁺ T cells, after a single stimulation that recognized both peptide-pulsed target cells to multiple gp 100 epitopes and a melanoma cell line that endogenously expressed gp 100 antigen. Conclusions CD83⁺ DCs transduced with rV-gp 100 are capable of generating a strong CD8⁺ T-cell response against melanoma tumor cells. Expression of melanoma antigens by mature DCs offers the potential advantage of presenting multiple endogenously processed T-cells epitopes and using multiple HLA restriction elements for antimelanoma vaccine therapy.     

Bacillus Calmette‐Guérin cell‐wall skeleton enhances the killing activity of cytotoxic lymphocyte‐activated human dendritic cells transduced with the prostate‐specific antigen gene

OBJECTIVE

To determine whether dendritic cells (DC) transduced with the prostate‐specific antigen (PSA) gene can induce PSA‐specific cytotoxic lymphocytes (CTL) against prostate cancer cells, and whether bacillus Calmette‐Guérin (BCG) cell‐wall skeleton (CWS) can enhance the maturation of DC‐PSA and the killing activity of subsequently induced PSA‐specific CTL.

MATERIALS AND METHODS

We generated an adenovirus encoding the PSA gene (AxCA‐PSA) using the cosmid‐terminal protein complex method. DC were infected with AxCA‐PSA using the centrifugal method. The ability of CTL to lyse target cells expressing PSA, i.e the PSA‐positive prostate cancer cell line, LNCap, and PSA‐transduced autologous phytohaemagglutinin (PHA) blasts expressing PSA, was assessed using the ⁵¹Cr‐release assay. The maturation of DC‐PSA stimulated by BCG‐CWS was assayed by flow cytometry. The cytotoxic activity enhanced by BCG‐CWS was assessed by the ⁵¹Cr‐release assay.

RESULTS

DC‐PSA induced PSA‐specific CTL with 85% cytotoxic activity against LNCaP (effector: target ratio, E:T, of 50:1). However, the cytotoxic activity against PSA‐negative cells was very low. Anti‐CD8 and anti‐major histocompatibility (MHC) class I antibodies blocked PSA‐specific cytotoxicity. The PSA‐specific killing was reproducible against autologous PHA blast cells expressing PSA, independently of human leukocyte antigen haplotype. Furthermore, the combination of DC‐PSA with BCG‐CWS remarkably enhanced the PSA‐specific cytotoxicity against PHA blasts expressing PSA (15–30% at an E:T ratio of 50:1).

CONCLUSION

These findings suggest that DC‐PSA can induce MHC class I‐restricted PSA‐specific CD8+ CTL responses and that DC‐PSA matured by BCG‐CWS enhance PSA‐specific cytotoxicity. The combination of DC‐PSA with BCG‐CWS might be a useful approach for treating advanced prostate cancer.     

Primary lymph-node staging with 68Ga-PSMA PET in high-risk prostate cancer: pathologic correlation with extended pelvic lymphadenectomy specimens

Aim of the studyThis study aims to assess the diagnostic efficacy of Gallium-68-prostate-specific membrane antigen positron emission tomography (PET)/computed tomography (CT) (68Ga PSMA PET-CT) in primary nodal staging of high-risk prostate cancer (PCa) when compared to pathologic findings of extended pelvic lymph-node dissection (eLND).Materials and methodsThe records of high-risk PCa patients who were preoperatively staged through 68Ga PSMA PET-CT and who underwent robot-assisted radical prostatectomy with eLND either alone or as part of multimodal definitive therapy between August 2016 and November 2019 were retrospectively reviewed. Surgeons were not blinded to the results of the 68Ga PSMA PET-CT scan. Pathologic uptake was defined as any anomalous uptake which was not better explained by another cause and was suggestive of PCa. The reference standard for this study was the pathologic confirmation using a node-based analysis. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy for 68Ga PSMA PET-CT were calculated in a per-patient analysis using IBM SPSS Statistics version 25.ResultsSeventeen patients met the selection criteria. Mean age was 63 years (range 44–77) and mean and median preoperative serum prostate specific antigen was 19.25 and 9 ng/ml (range 6–131), respectively. The most common pathologic Gleason score was 8 (52.9% of cases). Seven patients (41%) had positive surgical margins and were submitted to adjuvant radiotherapy. Mean number of per patient removed lymph-nodes was 13 (±2.19). 68Ga PSMA PET-CT showed findings compatible with lymph node metastases in 4/17 patients and with locally-confined disease in 13/17 patients. Following pathologic confirmation, the per-patient sensibility of the 68Ga PSMA PET-CT was calculated at 75% (1 false negative) and the specificity at 92.3% (1 false positive) for detection of lymph node metastasis on primary staging of high-risk PCa patients. Positive and negative predictive value were 75% and 92.3%, respectively; accuracy of the test was calculated at 88.2%. All patients were submitted to 68Ga PSMA PET-CT re-evaluation 6 months after surgery and tested negative for local, nodal, or distant recurrence of disease.Conclusions68Ga PSMA PET-CT appears to have a high negative predictive value for local lymph node metastases in high-risk primary PCa when compared to pathologic findings of eLND. Its role in the primary nodal staging of high-risk PCa patients worths further evaluation.     

Regression of Lymph Node Metastases by Immunotherapy Using Autologous Breast Tumor-Lysate Pulsed Dendritic Cells: Report of a Case

A 50-year-old woman was diagnosed as having stage IV breast cancer with bilateral supraclavicular lymph node metastasis resistant to CAF therapy. She received immunotherapy using autologous tumor lysate-pulsed dendritic cells (DCs). Four cycles of DC injection into the right supraclavicular lymph nodes resulted in regression of bilateral supraclavicular lymphogenous metastasis. Histological studies revealed an accumulation of CD45⁺ T lymphcytes in the regressive lymph nodes. This case suggests that immunotherapy with DCs may be a safe and promising approach for the treatment of advanced breast cancer. Received: July 27, 2000 / Accepted: January 9, 2001     

High expression of PSM-E correlated with tumor grade in prostate cancer: a new alternatively spliced variant of prostate-specific membrane antigen

BACKGROUND: Prostate-specific membrane antigen (PSMA) overexpressed in prostate cancer (PCa) has been targeted for therapy and diagnosis of PCa. In the current study, PSMA cDNA was cloned from PCa tissue by RT-PCR. After sequencing, a new spliced variant of PSMA (PSM-E) was discovered and its specificity in PCa was evaluated. METHODS: PSM-E and PSMA mRNA were measured in LNCaP, PC-3 and prostate or nonprostatic malignancies. Following transfection of PC-3 with PSM-E cDNA in the pcDNA3.0 vector, PSM-E expression was measured by immunofluorescence and Western-blot. PSM-E and PSMA mRNA levels were quantified by a real-time PCR assay in normal prostate (n = 7), benign prostatic hyperplasia (BPH) (n = 22) and PCa (n = 41). The correlation between their levels and tumor grade was analyzed. RESULTS: PSM-E cDNA is identical to PSMA except for a 97-nucleotide region and a 93-nucleotide region. PSM-E and PSMA mRNA were detected in PCa and LNCaP, not in PC-3; PSMA could be detected in some nonprostatic tumors whereas PSM-E not. The expression of PSM-E protein was detected in transfected cells. Significant difference of PSM-E mRNA levels was observed among normal prostate, BPH and PCa (P < 0.001), and PSM-E levels increased with increasing Gleason score (r = 0.514, P < 0.001). PSMA mRNA levels were higher in BPH and PCa than in normal prostate (P < 0.001), but no difference between BPH and PCa, no significant correlation was observed between PSMA levels and Gleason score (r = 0.229, P = 0.057). CONCLUSIONS: PSM-E may be a potential prognostic indicator for PCa progression and may be a new target antigen for therapy of PCa.     

Recombinant adenovirus mediated prostate-specific enzyme pro-drug gene therapy regulated by prostate-specific membrane antigen (PSMA) enhancer/promoter

Gene directed enzyme pro-drug therapy (GDEPT) is one of the adjuvant therapeutic regimens for advanced prostate adenocarcinoma, and this research intended to explore how to apply targeting therapy of prostate adenocarcinoma under the mediation of a promoter/enhancer of prostate-specific membrane antigen (PSMA(EP)) as a specific regulatory element. Recombinant adenoviruses (Ad-PSMA(E-P)-enhanced green fluorescent protein [EGFP], Ad-CMV-EGFP, Ad-PSMA(E-P)-CD, and Ad-CMV-CD) were constructed and could express cytosine deaminase (CD) or the EGFP reporter gene driven by a PSMA(EP) or cytomegalovirus (CMV) promoter. LNCaP, CL-1, MCF-7, and A549 were infected with CD-produced recombinant adenoviruses and treated with pro-drug 5-fluorocytosine (5-FC) in vivo and vitro; then, the growth inhibition of the cells and the cell cycle variation were assessed by an [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay and flow cytometry. Growth suppression of the xenograft tumor was also adopted to evaluate the efficiency of the suicide system. Morphologic changes after treatment in vivo were assessed with hematoxylin and eosin staining. In the 4 examined cancer cell lines, PSMA-positive prostate cancer cells LNCap and CL-1 were exclusively sensitive to the Ad-PSMA(E-P)-CD/5-FC system. The S phase of cell cycle arrest was thought to be involved in the cytotoxicity of 5-fluorouracil (5-FU) converted from 5-FC by CD. CL-1 implanted Athymic BALB/c mice showed growth inhibition of tumors when they were treated with the Ad-PSMA(E-P)-CD/5-FC system without systemic conversion toxicity. The PSMA-based, CD-produced adenovirus, deserving further investigation in the future, might be a good candidate for targeting gene therapy of prostate adenocarcinoma.     

Induction of cytolytic T lymphocytes against pediatric solid tumors in vitro using autologous dendritic cells pulsed with necrotic primary tumor

Purpose

Effective and generally applicable methods for generating cancer vaccines in children have not been defined. Dendritic cells (DCs) are the most potent professional antigen-presenting cells capable of activating primary cytolytic T cells. We tested the ability of DCs generated from pediatric patients' peripheral blood monocytes and pulsed with a necrotic tumor to activate autologous tumor-specific cytolytic T cells.

Methods

Tumor and peripheral blood cells were obtained from pediatric patients undergoing biopsy or resection for advanced solid tumors according to an institutional research board-approved protocol and after acquiring informed consent from them. To generate DCs, we treated peripheral blood monocytes with granulocyte-macrophage colony stimulating factor and interleukin (IL)-4. Maturation was induced with a cytokine cocktail (CC) containing tumor necrosis factor-α, IL-6, IL-1β, and prostaglandin E₂. The DC phenotype was assayed using flow cytometry. Tumor necrosis was induced by exposure to UV-B irradiation (1000 mJ). Dendritic cells pulsed with a UV-B-treated primary tumor and matured with CC were used to stimulate autologous peripheral blood lymphocytes weekly. Tumor-specific cytolytic activity was assayed using 4-hour ⁵¹Cr release.

Results

Peripheral blood monocytes isolated from pediatric patients differentiated into immature DCs (CD14⁻, MHCII⁺ [major histocompatibility complex], CD80^low, CD86^low) in the presence of granulocyte-macrophage colony stimulating factor and IL-4. Cytokine cocktail induced maturation of DCs, as characterized by increased expressions of MHCII, CD83, CD80, and CD86. Patients' peripheral blood lymphocytes stimulated in vitro with DCs loaded with a necrotic primary tumor and matured with CC specifically lysed autologous neuroblastoma in 7 of 9 patients.

Conclusion

Dendritic cells generated from the peripheral blood of children with advanced solid tumors and pulsed with a necrotic primary tumor undergo maturation and effectively stimulate autologous tumor-specific cytolytic T cells in vitro. We describe a simple method for generating a vaccine capable of activating cytotoxic T cells against pediatric solid tumors that does not require the genetic identification of tumor-associated antigens.     

In vitro induction of tumor-specific HLA class I-restricted CD8+ cytotoxic T lymphocytes from patients with locally advanced breast cancer by tumor antigen-pulsed autologous dendritic cells

BACKGROUND: Early dissemination of treatment-resistant tumor cells remains the major cause of metastatic recurrence and death in breast cancer patients. Dendritic cells (DCs) are the most powerful antigen-presenting cells, and recently DC-based vaccination has shown great promise for the treatment of human malignancies by immunological intervention. MATERIALS AND METHODS: CD8+ T lymphocytes derived from peripheral blood mononuclear cells stimulated in vitro with autologous breast tumor antigen-pulsed DCs were tested for their ability to induce a HLA class I restricted cytotoxic T lymphocyte (CTL) response against autologous tumor cells. To correlate cytotoxic activity by CTL with T cell phenotype, two-color flow cytometric analysis of surface markers and intracellular cytokine expression was performed. RESULTS: DC pulsed with breast tumor extracts consistently elicited a tumor-specific HLA class I restricted CTL response in vitro in three consecutive patients harboring locally advanced breast cancer. CTL expressed strong cytolytic activity against autologous tumor cells but did not lyse autologous Epstein Barr virus-transformed lymphoblastoid cell lines and showed variable cytotoxicity against the natural killer-sensitive cell line K-562. In all patients, two color flow cytometric analysis of surface markers and intracellular cytokine expression demonstrated that tumor-specific CTL exhibited an heterogeneous CD8+/CD56+ expression and a striking Th1 cytokine bias (IFNgamma(high)/IL-4 (low)). CONCLUSIONS: Tumor lysate-pulsed DCs can consistently stimulate specific CD8+ CTLs able to kill autologous tumor cells in patients with locally advanced breast cancer in vitro. Tumor antigen-pulsed DC-based vaccinations may be appropriate for the treatment of residual and/or chemotherapy-resistant breast cancer refractory to standard salvage treatment modalities.     

Presentation of prostate tumor antigens by dendritic cells stimulates T-cell proliferation and cytotoxicity

Dendritic cells (DCs) are “professional” antigen-presenting cells capable of stimulating T-cell proliferation and cytotoxicity when loaded with and presenting specific antigens, including tumor antigens. We demonstrated the stimulation of an autologous cytotoxic T-cell response elicited by DC loaded with autologous tumor cell lysate derived from primary prostate tumor. A candidate tumor antigen is prostate-specific membrane antigen (PSMA), which is overexpressed in prostate cancer patients. We identified a HLA-A2 motif in PSMA, isolated patient DC, loaded peptide into DC, and stimulated autologous T cells to proliferate. The ability to use DC for presentation of either tumor or peptide antigen in an HLA-restricted fashion in order to stimulate T-cell proliferation and cytotoxicity demonstrates the potential of this technology for development of a prostate cancer vaccine. © 1996 Wiley-Liss, Inc.     

Induction of tumor-specific cytotoxic T lymphocytes in cancer patients by autologous tumor RNA-transfected dendritic cells

OBJECTIVE: To demonstrate the feasibility of inducing tumor antigen-specific immune responses in patients with metastatic cancer using total tumor RNA-loaded dendritic cells (DCs). SUMMARY BACKGROUND DATA: The authors have shown that DCs transfected with mRNA encoding defined tumor antigens induce tumor antigen-specific T-cell responses in vitro and in vivo. There may be significant advantages to inducing immune responses against the entire repertoire of antigens expressed by a patient's autologous tumor. METHODS: RNA was extracted from a metastatic colon cancer and used to load autologous DCs. The DCs were coincubated with autologous T cells and the cytolytic activity of the T cells was assessed by the ability to lyse the autologous tumor cells. RNA was then extracted from a metastatic lung cancer and used to load autologous DCs, followed by four injections of the DC vaccine given every 4 weeks. Tumor antigen-specific cytotoxic T lymphocyte activity was then evaluated by testing peripheral blood mononuclear cells for their ability to lyse an antigen-expressing target. RESULTS: DCs transfected with the total RNA content of autologous tumor cells stimulated antigen-specific T-cell responses that are capable of recognizing and lysing autologous, primary tumor cells in vitro. Tumor-specific immune responses were induced in a patient with a carcinoembryonic antigen-expressing adenocarcinoma after immunization with autologous DCs transfected with total tumor RNA. CONCLUSIONS: DCs transfected with total tumor RNA may represent a method for inducing immune responses against the entire repertoire of tumor antigens of surgically resected malignancies.     

Vaccination of hormone-refractory prostate cancer patients with peptide cocktail-loaded dendritic cells: results of a phase I clinical trial

BACKGROUND: Immunotherapies might represent promising alternatives for the treatment of patients with hormone-refractory prostate cancer (HRPC). In a Phase I clinical trial, we evaluated a vaccination with dendritic cells (DCs) loaded with a cocktail consisting of HLA-A*0201-restricted peptides derived from five different prostate cancer-associated antigens [prostate-specific antigen (PSA), prostate-specific membrane antigen (PSMA), survivin, prostein, transient receptor potential p8 (trp-p8)]. METHODS: Eight HRPC patients received a total of four vaccinations every other week. Clinical and immunological responses were monitored by the determination of the serum PSA levels and by enzyme linked immunospot (ELISPOT) analyses, respectively. RESULTS: Apart from local skin reactions no side effects were noted. One patient displayed a partial response (PR; PSA decrease >50%) and three other patients showed stable PSA values or decelerated PSA increases. In ELISPOT analyses, three of four PSA responders also showed antigen-specific CD8+ T-cell activation against prostein, survivin, and PSMA. CONCLUSIONS: The described protocol represents a safe and feasible concept for the induction of clinical and immunological responses. The application of a peptide cocktail-derived from different antigens as a novel treatment modality is supposed to allow for the genetic and biologic heterogeneity of PCa.