Double-stranded RNA (dsRNA) is produced during the replication cycle of most viruses and triggers antiviral immune responses through Toll-like receptor 3 (TLR3). However, the molecular mechanisms and subcellular compartments associated with dsRNA-TLR3-mediated signaling are largely unknown. Here we show that c-Src tyrosine kinase is activated by dsRNA in human monocyte-derived dendritic cells, and is recruited to TLR3 in a dsRNAdependent manner. DsRNA-induced activation of interferon-regulatory factor 3 and signal transducer and activator of transcription 1 was abolished in Src kinase-deficient cells, and restored by adding back c-Src, suggesting a central role of c-Src in antiviral immunity. We also provide evidence that TLR3 is localized in the endoplasmic reticulum of unstimulated cells, moves to dsRNA-containing endosomes in response to dsRNA, and colocalizes with c-Src on endosomes containing dsRNA in the lumen. These results provide novel insight into the molecular mechanisms of TLR3-mediated signaling, which may contribute to the understanding of innate immune responses during viral infections.

Background Patients with high‐risk prostate cancer (PC) can experience biochemical relapse (BCR), despite surgery, and develop noncurative disease. The present study aimed to reduce the risk of BCR with a personalized dendritic cell (DC) vaccine, given as adjuvant therapy, after robot‐assisted laparoscopic prostatectomy (RALP). Methods Twelve weeks after RALP, 20 patients with high‐risk PC and undetectable PSA received DC vaccinations for 3 years or until BCR. The primary endpoint was the time to BCR. The immune response was assessed 7 weeks after surgery (baseline) and at one‐time point during the vaccination period. Results Among 20 patients, 11 were BCR‐free over a median of 96 months (range: 84–99). The median time from the end of vaccinations to the last follow‐up was 57 months (range: 45–60). Nine patients developed BCR, either during (n = 4) or after (n = 5) the vaccination period. Among five patients diagnosed with intraductal carcinoma, three experienced early BCR during the vaccination period. All patients that developed BCR remained in stable disease within a median of 99 months (range: 74–99). The baseline immune response was significantly associated with the immune response during the vaccination period (p = 0.015). For patients diagnosed with extraprostatic extension (EPE), time to BCR was longer in vaccine responders than in non‐responders (p = 0.09). Among 12 patients with the International Society of Urological Pathology (ISUP) grade 5 PC, five achieved remission after 84 months, and all mounted immune responses. Conclusion Patients diagnosed with EPE and ISUP grade 5 PC were at particularly high risk of developing postsurgical BCR. In this subgroup, the vaccine response was related to a reduced BCR incidence. The vaccine was safe, without side effects. This adjuvant first‐in‐man Phase I/II DC vaccine study showed promising results. DC vaccines after curative surgery should be investigated further in a larger cohort of patients with high‐risk PC.

Prostate cancer patients diagnosed with high Gleason score (≥ 8) and large tumors (≥T2c) are considered high-risk patients and >50% will develop an early biochemical relapse. Presently, there is no curative therapy available for patients with biochemical relapse. Based on these findings we initiated in January 2011 a Phase I/II dendritic cell (DC) vaccine study. Patients included have pathological stage pT2 - pT3b, Gleason score 7b-10, pN0, pN+ or pNx and postoperative PSA < 0.2 μg/L. Following surgery autologous tumor cell lines were established from each patient using an in-house culturing method. mRNA from the tumor cell line was produced and used for DC vaccination in combination with mRNA hTERT and mRNA Survivin. DCs were differentiated from enriched monocytes, cultured for 2 days with IL4 and GM-CSF and matured with Jonuleit-maturation cocktail for 24 hours. The matured DCs were transfected separately with the 3 different mRNAs and then frozen and stored until use. The vaccination regimen includes one vaccine per week for four weeks, followed by monthly “vaccine boost” during the first year, then every 3 months the second and third year. Recently, a novel 3 days DC protocol using a TLR7/8-agonist maturation cocktail has been implemented at our department. Based on encouraging clinical results with this type of DCs in compassionate use patients with different types of tumors, we decided to change our DCs protocol to the new generation DCs. Of the 20 patients included in this trial 15 patients have been given the standard fast DCs and 5 have been vaccinated with the new type of DCs. 8 Patients given standard DC has completed 3 years of vaccination and 4 has completed 2 years of vaccination. 3 of 15 patient given standard DC has experienced PSA relapse during vaccination. None of the patients given the new type of DC has so far experienced raise in PSA levels. To our knowledge this is the first adjuvant DC vaccine study in high risk prostate cancer and we conclude that the study is feasible, safe and utmost promising. Extensive immune monitoring is ongoing taking advantage of the established autologous tumor cell lines from all patients. Citation Format: Anne Merete Aa. Tryggestad, Karol Axcrona, Iris Bigalke, Else M. Inderberg-Suso, Gjertrud Skorstad, Ulrika Axcrona, Steinar Aamdal, Gustav Gaudernack, Dolores Schendel, Wolfgang Lilleby, Svein Dueland, Gunnar Kvalheim. Clinical results of a Phase I/II trial of adjuvant therapeutic vaccination in high risk resected prostate cancer patients using autologous dendritic cells loaded with mRNA from primary prostate cancer tissue, hTERT and survivin. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2235.

324 Background: Patients with very high-risk prostate cancer (VHR-PC) features experience worse outcome after radical prostatectomy. This study was designed to assess biochemical failure and toxicity of adjuvant dendritic cells vaccine (DCV) in prostate cancer patients who are at greatest risk for cancer progression. Methods: Twenty patients with pathological stage pT2 - pT3b and Gleason score 7B-10, pN0, pN+ or pNx were enrolled into the approved study DC-005. The primary end point was clinical failure. Ten patients were tested for disseminated tumor cells (DTCs) to the bone marrow before inclusion to the study. Three patients out of 10 patients had positive DTCs detection in bone marrow. The mean age of the cohort was 63 years (SD 6.9 years), and three patients had postsurgical pN1 status. Eighteen patients had two or more high-risk factors (ISUP grade 5, T3- stage and or PSA > 20 ng/mL). Autologous dendritic cells were transfected with mRNA for hTERT, survivin and tumor mRNA. The DCV product was applied intradermally after curative intended surgery once per week the first months, then once per months the first year, thereafter every 3 months for two years or until biochemical progression (PSA relapse cut-off ≥ 0.3). Results: After 5 years follow-up (FU) 62% (12/20 patients) had not biochemically progressed and with a median FU of 69 months all patients included in the study are alive. Five patients were treated with salvage and one patient with adjuvant radiation treatment, three patients received limited ADT, and three patients are on first line ADT, none of those eight patients have experienced castration resistant prostate cancer. The toxicity was mild with no serious adverse event related to DCV. Conclusions: Adjuvant DCV mitigates the time to biochemical progression. These results appear favorably compared to historical controls in VHR-PC. The clinical outcomes of this study warrants a future enlarged clinical trial. Clinical trial information: NCT01197625.

Prostate cancer patients diagnosed with high Gleason score (≥ 8) and large tumors (≥T2c) are considered high-risk patients and >50% will develop an early biochemical relapse following radical surgery. Presently, there is no curative therapy available for patients once when biochemical relapse occur. Based on encouraging clinical results from 6 relapsed prostate cancer patients treated under hospital exemption with dendritic cell (DC) vaccines we started an adjuvant, first in man, phase I/II study using autologous, monocyte derived DCs targeting autologous tumor antigens from primary tumor, combined with hTERT and survivin. Twenty patients were included in the study. All patients had pathological stage pT2-pT3b and Gleason score 7b-10. Following surgery prostate specific antigen (PSA) was < 0,2 µg/L in all patients. Fifteen patients have received 3-days DCs generated according to our standard protocol with a maturation cocktail composed of GM-CSF, IL-4, TNFα, IL1β and PgE2. Five patients were treated with a TLR 7/8 ligand containing maturation cocktail, resulting in DCs with a polarized release of IL-12p70 and no or low IL-10. The patients received 4 weekly vaccinations, then DTH vaccine at week 8 and thereafter-monthly vaccinations the first year, and every third month the second and third year. All patients except of two have completed vaccination. Of the 15 first patients using the standard DCs, three patients developed PSA relapse during vaccination (PSA measured twice >0,5 μg/L with minimum 4 weeks interval) and two additional patients relapsed after completed 3 years of vaccination. From the last 5 patients given the new type of DCs none have experienced PSA relapse. Seventy-five percent of the patients remain without biochemical relapse with a mean observation time of 47,5 (range 29-82) months. We confirm that the study is feasible and safe. Immune responses in the patients are under investigation. Altogether, our clinical results are promising and the use of adjuvant DC vaccines might become a new approach to prevent biochemical relapse in high-risk prostate cancer patients following radical surgery. Citation Format: Anne Merete Tryggestad, Iris Bigalke, Karol Axcrona, Bjørn Brennhovd, T Kirsti Hønnåshagen, Lisbeth Skoge, Lena Tjeldhorn, Lene Mowinckel, Stein Sæbøe-Larsen, Jens A L Jørgensen, Grete S Andreassen, Gjertrud Skorstad, Dag Josefsen, Ulrika Axcrona, Steinar Aamadal, Wolfgang Lilleby, Svein Dueland, Gunnar Kvalheim. A first in man phase I/II adjuvant dendritic cell vaccine study in high-risk prostate cancer patients following radical surgery reduce the incidence of biochemical relapse [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT016.