Tumor antigen-pulsed DC vaccine(Sichuan University)

To investigate the therapeutic effect of Toll-like receptor 7( TLR7) agonist imiquimod combined with dendritic cell( DC)-based tumor vaccine on melanoma in mice and the potential mechanism.

Melanoma-bearing mouse models were established by subcutanous injection of B16-OVA cells into C57 BL /6 mice. DCs were isolated from mouse bone marrow and propagated in culture medium with recombinant mouse granulocyte-macrophage colony-stimulating factor( rm GM-CSF) and recombinant mouse interleukin-4( rm IL-4). DC vaccine( OVA-DC) was prepared by overnight incubation of DCs added with chicken ovalbumin. C57 BL /6 mice were separated into four groups which were treated with PBS,topical imiquimod application,OVA-DC intradermal injection and imiquimod plus OVA-DC,respectively. The tumor size was calculated by digital vernier caliper. Peripheral blood CD4~+FOXP3~+Tregs of the tumor-bearing mice was detected by flow cytometry. The cytotoxicity of splenic lymphocyte against B16-OVA was assessed in vitro by CCK-8 assay.

Compared with the other three groups,B16-OVA-bearing mice treated with imiquimod plus DC vaccine had the smallest tumor volume. The percentage of CD4~+FOXP3~+Tregs decreased significantly in the combined treated mice. The combined treatment enhanced significantly cytotoxicity of splenic lymphocytes against B16-OVA cells.

Imiquimod combined with antigen-pulsed-DC vaccine could reduce CD4~+FOXP3~+Treg proportion and promote anti-tumor effect in mice with melanoma

This phase I study was performed to assess the safety and immune response of tumor cell-pulsed dendritic cell (DC) vaccine therapy against cancer patients with multiple metastases. DCs, generated from adherent cells of peripheral blood mononuclear cells (PBMCs) using interleukin-4 (IL-4) and granulocyte/monocyte colony-stimulating factor, were loaded with autologous necrotic whole tumor cells. Thereafter, the DCs were matured with culture supernatants of OK-432-stimulated PBMCs. Activated lymphocytes were also induced from non-adherent cells of PBMCs using OKT-3 and IL-2. Patients received a subcutaneous injection of DCs loaded with tumor cells every 2 weeks and received an intravenous injection of activated lymphocytes every 4 weeks. This combination therapy was named tumor-pulsed DC vaccine therapy. Tumor-pulsed DC vaccine therapy was continued as long as possible in 19 patients. No particular adverse reactions, except for low-grade fever, were found. The patients could be divided into two groups according to the survival time, i.e., 6 responders (long survival patients) and 13 non-responders (short survival patients). Based on the laboratory data of responders, eligibility criteria were determined. Using the eligibility criteria, a phase I/II study was recently performed with 15 patients. A delayed-type hypersensitivity reaction against tumor-pulsed DCs became positive in 13 of the 15 patients within 6 months after the therapy. This therapy was again safe, and no evidence of autoimmune disease was noted. The survival time of these 15 patients was significantly prolonged compared with that of the 13 non-responders of the phase I study (p < 0.0001). This continuous tumor-pulsed DC vaccine therapy was well tolerated in patients with disseminated carcinomas.