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Objective To assess whether a specific cytotoxic T-cell response can be induced in patients with prostate cancer after cryoablation.Methods Twenty Patients with high-risk prostate cancer underwent cryoablation.Blood was sampled prior to,4 and 8 weeks after treatment.Serum cytokine levels were analyzed by ELISA,and the Th1/Th2 ratio was estimated from the IFN-gamma/IL-4 ratio.Peripheral blood mononuclear cells (PBMC) were stimulated with autologous prostate cancer-derived protein lysates,and frequency of tumor-specific T-cells was tested ex vivo in an IFN-gamma ELISPOT assay.To assess cytolytic activity,T-cells were co-incubated with human prostate cancer cells,LNCaP,or with renal cancer cells,GRC-1,and release of cytosolic adenylate kinase was measured by a luciferase assay.Result Four weeks after cryoablation significantly higher levels of TNF-alpha and IFN-gamma were observed compared to before treatment,and to 8 weeks after treatment.No changes in IL-4 or IL-10 were observed.The Th1/Th2 ratio (10.47 ± 0.80),4 weeks after treatment,was increased compared to before treatment (3.98 ± 0.45),but decreased 8 weeks later (7.65±0.64).Tumor-specific T-cell responses were evident after cryosurgery in PBMC.Cytolytic activity against LNCaP was increased 4 weeks after treatment compared to before treatment (594.49 ±154.84 versus 4.20±0.68,P<0.01),but was decreased 8 weeks later (79.70±18.73).No response was found in cytolytic activity against GRC-1.Conclusions Cryoablation of prostate cancer can improve tumor-specific cytotoxic T-cell stimulation with a dramatically increased tumor specific cytolytic activity.However,the response is not sufficiently maintained to prevent cancer relapse.