Phase I/II trial of melanoma therapy with dendritic cells transfected with autologous tumor-mRNA.

We have developed an individualized melanoma vaccine based on transfection of autologous dendritic cells (DCs) with autologous tumor-mRNA. Dendritic cells loaded with complete tumor-mRNA may generate an immune response against a broad repertoire of antigens, including unique patient-specific antigens. The purpose of the present phase I/II trial was to evaluate the feasibility and safety of the vaccine, and the ability of the DCs to elicit T-cell responses in melanoma patients. Further, we compared intradermal (i.d.) and intranodal (i.n.) vaccine administration. Twenty-two patients with advanced malignant melanoma were included, each receiving four weekly vaccines. Monocyte-derived DCs were transfected with tumor-mRNA by electroporation, matured and cryopreserved. We obtained successful vaccine production for all patients elected. No serious adverse effects were observed. A vaccine-specific immune response was demonstrated in 9/19 patients evaluable by T-cell assays (T-cell proliferation/interferon-gamma ELISPOT) and in 8/18 patients evaluable by delayed-type hypersensitivity (DTH) reaction. The response was demonstrated in 7/10 patients vaccinated intradermally and in 3/12 patients vaccinated intranodally. We conclude that immuno-gene-therapy with the described DC-vaccine is feasible and safe, and that the vaccine can elicit in vivo T-cell responses against antigens encoded by the transfected tumor-mRNA. The response rates do not suggest an advantage in applying i.n. vaccination.

Immunotherapy with allotumour mRNA-transfected dendritic cells in androgen-resistant prostate cancer patients.

Here, we present results from a clinical trial employing a new vaccination method using dendritic cells (DCs) transfected with mRNA from allogeneic prostate cancer cell lines (DU145, LNCaP and PC-3). In all, 20 patients were enrolled and 19 have completed vaccination. Each patient received at least four weekly injections with 2 x 10(7) transfected DCs either intranodally or intradermally. Safety and feasibility of vaccination were determined. Immune responses were measured as delayed-type hypersensitivity and by in vitro immunoassays including ELISPOT and T-cell proliferation in pre- and postvaccination peripheral blood samples. Serum prostate-specific antigen (PSA) levels and bone scans were monitored. No toxicity or serious adverse events related to vaccinations were observed. A total of 12 patients developed a specific immune response to tumour mRNA-transfected DCs. In total, 13 patients showed a decrease in log slope PSA. This effect was strengthened by booster vaccinations. Clinical outcome was significantly related to immune responses (n = 19, P = 0.002, r = 0.68). Vaccination with mRNA-transfected DCs is safe and results in cellular immune responses specific for antigens encoded by mRNA derived from the prostate cancer cell lines. The observation that in some patients vaccination affected the PSA level suggests that this approach may become useful as a treatment modality for prostate cancer patients.

A protocol for generation of clinical grade mRNA-transfected monocyte-derived dendritic cells for cancer vaccines.

With the aim of producing large quantities of mRNA-transfected monocyte-derived dendritic cells (DCs) to be used as cancer vaccines, a new clinical grade procedure has been developed. Peripheral blood mononuclear cells (PBMCs) obtained by leukapheresis were enriched for monocytes by immunomagnetic depletion of CD19+ B cells and CD2+ T cells employing the ISOLEX 300i device. After 5 days of culture of enriched monocytes in gas permeable Teflon bags, using serum-free medium supplemented with granulocyte/macrophage-colony stimulating factor and interleukin-4 (IL-4), immature DCs were generated. Following transfection with mRNA from three human prostate cancer cell lines (DU145, LNCaP and PC-3), employing a newly developed square wave electroporation procedure, the immature DCs were immediately transferred to Teflon bags and matured for 48 h, using serum-free medium supplemented with IL-1alpha, IL-6, tumour necrosis factor-alpha and PGE2. The electroporation procedure efficiently transferred mRNA into the DCs with minor effect on the viability of the cells. The generated matured transfected DCs show high expression of the antigens CD83, CD80, CD86 and human leucocyte antigen-DR. Freezing and thawing of the transfected matured DCs had minor effect on cell viability and the phenotype. From 4 x 109 PBMCs, about 1 x 108 transfected matured DCs are produced. The thawed transfected DCs were able to elicit primary T-cell responses in vitro against antigens encoded by the prostate cancer mRNA as shown by enzyme-linked immunospot assay using mock-transfected DCs as control. Based on these results, clinical trials in cancer patients have been initiated.