Tumour cell-based vaccines for the treatment of melanoma

Whole tumor antigen vaccination using dendritic cells: comparison of RNA electroporation and pulsing with UV-irradiated tumor cells

Because of the lack of full characterization of tumor associated antigens for solid tumors, whole antigen use is a convenient approach to tumor vaccination. Tumor RNA and apoptotic tumor cells have been used as a source of whole tumor antigen to prepare dendritic cell (DC) based tumor vaccines, but their efficacy has not been directly compared. Here we compare directly RNA electroporation and pulsing of DCs with whole tumor cells killed by ultraviolet (UV) B radiation using a convenient tumor model expressing human papilloma virus (HPV) E6 and E7 oncogenes. Although both approaches led to DCs presenting tumor antigen, electroporation with tumor cell total RNA induced a significantly higher frequency of tumor-reactive IFN-gamma secreting T cells, and E7-specific CD8+ lymphocytes compared to pulsing with UV-irradiated tumor cells. DCs electroporated with tumor cell RNA induced a larger tumor infiltration by T cells and produced a significantly stronger delay in tumor growth compared to DCs pulsed with UV-irradiated tumor cells. We conclude that electroporation with whole tumor cell RNA and pulsing with UV-irradiated tumor cells are both effective in eliciting antitumor immune response, but RNA electroporation results in more potent tumor vaccination under the examined experimental conditions.

Therapeutic vaccines for melanoma: current status

Considerable clinical research is focused on improving systemic treatments for melanoma. Unfortunately, the disease is generally resistant to standard chemotherapy, and surgical excision remains the best treatment option whenever possible. However, complete spontaneous regression of melanoma has been observed in some patients, a phenomenon thought to be mediated by the immune system. This has stimulated attempts to manipulate the immune system for therapeutic purposes. Vaccination is a form of active specific immunotherapy, such that the response against the tumor is actively generated by the patient's immune system, and is directed against a particular cellular target or specific membrane antigen. Numerous approaches to vaccination for melanoma have been investigated, and have become more complex as our understanding of anti-tumor immunity has increased. Vaccines have been shown to induce measurable immunologic responses that may be correlated with improved clinical outcomes in patients with melanoma. Large phase III clinical trials using peptide, ganglioside, and whole-cell tumor antigens are ongoing. Although anti-tumor vaccination has shown promising results in patients with melanoma, to date no vaccine has been approved for routine therapy of melanoma. Recently, a phase III trial evaluating the Canvaxin whole-cell vaccine in stage IV melanoma was halted because of a low likelihood of significant benefit. However, a larger phase III trial for patients with stage III disease was continued and results are awaited with interest.