Tumour cell lysate-loaded dendritic cell vaccine induces biochemical and memory immune response in castration-resistant prostate cancer patients

Abstract

Background: Recently, we produced a tumour antigen-presenting cells (TAPCells) vaccine using a melanoma cell lysate, called TRIMEL, as an antigen source and an activation factor. Tumour antigen-presenting cells induced immunological responses and increased melanoma patient survival. Herein, we investigated the effect of TAPCells loaded with prostate cancer cell lysates (PCCL) as an antigen source, and TRIMEL as a dendritic cell (DC) activation factor; which were co-injected with the Concholepas concholepas haemocyanin (CCH) as an adjuvant on castration-resistant prostate cancer (CRPC) patients.

Methods: The lysate mix capacity, for inducing T-cell activation, was analysed by flow cytometry and Elispot. Delayed-type hypersensitivity (DTH) reaction against PCCL, frequency of CD8(+) memory T cells (Tm) in blood and prostate-specific antigen (PSA) levels in serum were measured in treated patients.

Results: The lysate mix induced functional mature DCs that were capable of activating PCCL-specific T cells. No relevant adverse reactions were observed. Six out of 14 patients showed a significant decrease in levels of PSA. DTH(+) patients showed a prolonged PSA doubling-time after treatment. Expansion of functional central and effector CD8(+) Tm were detected.

Conclusion: Treatment of CRPC patients with lysate-loaded TAPCells and CCH as an adjuvant is safe: generating biochemical and memory immune responses. However, the limited number of cases requires confirmation in a phase II clinical trial.

Figure 1

PCCL, together with TRIMEL and TNF-α, induces a fast differentiation of active APCs (TAPCells) from peripheral blood monocytes. (A) PBMCs from healthy donors (n=3) were incubated in supplemented AIM-V medium. Next, adherent cells were stimulated for 24 h with TNF-α (20 U ml^–1), TNF-α+TRIMEL (100 mg ml^–1) (Trimel), TNF-α+PCCL (100 mg ml^–1) (PCCL100), TNF-α+PCCL (90 mg ml^–1)+TRIMEL (10 mg ml^–1) (PCCL90+Trimel10) or TNF-α+PCCL (80 mg ml^–1)+TRIMEL (20 mg ml^–1) (PCCL80+Trimel20). AM, non-stimulated monocytes. Expression of MHC molecules and maturation markers were determined using flow cytometry over CD11c⁺ population. Graphics represent mean fold induction relative to AM (*P<0.05, t-test). (B) Stimulated (filled figures) and non-stimulated (clear figures) PBLs from healthy donors (n=3) were cultured with PCCL-loaded APCs (PCCL80+Trimel20) for 16 h. IFN-γ secretion was measured by ELISPOT assay. Experiments were performed in triplicate (*P<0.05, **P<0.01, ANOVA). Every symbol (circle, square and rhombus) represents a different donor.

Figure 2

PCCL-loaded TAPCells immunotherapy is able to induce specific immune response in CRPC patients. (A) PBMCs obtained before (filled circles) or at the end of treatment (clear circles) were co-cultured with DCs loaded with PCCL and in vitro immune response was evaluated by IFN-γ ELISPOT assay. Graphics are representative of four patients. (B) DTH test against tumour lysate. Thirty days after the fourth immunisation, patients were inoculated subcutaneously with PCCL, CCH, KLH or saline solution (Ctrl). Skin inflammatory reaction was evaluated 48 h later. Pictures are representative of two patients. Experiments were performed in triplicate (*P<0.05, **P<0.01, ANOVA).

Figure 3

PCCL-loaded TAPCells immunotherapy increases IFN-γ-producing memory T-cell population. PBMCs obtained before the first immunisation (Pre) and at DTH test time (Post) were co-cultured overnight with autologous PCCL-loaded TAPCells, and analysed by FACS. (A) Proportion of CD45RO⁺ T cells over CD8⁺ population. (B) Proportion of IFN-γ⁺ T cells over CD8⁺ CD45RO⁺ population (P<0.05 t-test).

Figure 4

PCCL-loaded TAPCells immunotherapy reduces serum PSA levels. Serum PSA was evaluated monthly from the treatment onset until DTH test. Graphic shows change of PSA from baseline. The PSA Nadir is the absolute lowest level that the PSA drops after treatment. Every bar corresponds to a different patient.

Figure 5

Treatment improves PSADT in immunologic-responder patients. PSADT was calculated using all available previous PSA. (A) Mean of PSADT in all-treated group. (B) Mean of PSADT by immunologic response, determined by DTH test (P<0.05, ANOVA).