Vaccination of melanoma patients with peptide- or tumor lysate-pulsed dendritic cells.

Melanoma is the main cause of death in patients with skin cancer. Cytotoxic T lymphocytes (CTLs) attack melanoma cells in an HLA-restricted and tumor antigen-specific manner. Several melanoma-associated tumor antigens have been identified. These antigens are suitable candidates for a vaccination therapy of melanoma. Dendritic cells (DCs) are antigen-presenting cells (APCs) specialized for the induction of a primary T-cell response. Mouse studies have demonstrated the potent capacity of DCs to induce antitumor immunity. In the present clinical pilot study, DCs were generated in the presence of granulocyte/macrophage-colony stimulating factor (GM-CSF) and interleukin 4 (IL-4) and were pulsed with tumor lysate or a cocktail of peptides known to be recognized by CTLs, depending on the patient's HLA haplotype. Keyhole limpet hemocyanin (KLH) was added as a CD4 helper antigen and immunological tracer molecule. Sixteen patients with advanced melanoma were immunized on an outpatient basis. Vaccination was well tolerated. No physical sign of autoimmunity was detected in any of the patients. DC vaccination induced delayed-type hypersensitivity (DTH) reactivity toward KLH in all patients, as well as a positive DTH reaction to peptide-pulsed DCs in 11 patients. Recruitment of peptide-specific CTLs to the DTH challenge site was also demonstrated. Therefore, antigen-specific immunity was induced during DC vaccination. Objective responses were evident in 5 out of 16 evaluated patients (two complete responses, three partial responses) with regression of metastases in various organs (skin, soft tissue, lung, pancreas) and one additional minor response. These data indicate that vaccination with autologous DCs generated from peripheral blood is a safe and promising approach in the treatment of metastatic melanoma. Further studies are necessary to demonstrate clinical effectiveness and impact on the survival of melanoma patients.

Dendritic cells generated from peripheral blood transfected with human tyrosinase induce specific T cell activation.

Peptides of melanosomal proteins have recently been shown to be recognized in an HLA-restricted mode by specific cytolytic T lymphocytes in melanoma patients. Dendritic antigen-presenting cells (DC) are considered to be the most effective stimulators of T cell responses, and the use of these cells has therefore been proposed to generate therapeutic responses to tumor antigens in cancer patients. We, therefore, generated DC from peripheral blood of normal donors in the presence of granulocyte/macrophage colony-stimulating factor and interleukin-4. Flow cytometric analysis of the cells during a 2-week culture revealed a loss of CD14 and CD34 expression, a concomittent increase of CD1a, CD11a,b and c, CD44, CD45, CD54, HLA-class I and II, and intermediate levels of CD26, CD80 and CD86. Cultured DC stimulated proliferation of allogeneic T cells and induced a marked, up to 20-fold, stimulation of T cell proliferation after pulsing with tetanus toxoid. To achieve independence of already-identified antigenic peptides presented in HLA class I-restricted fashion, which limits the general applicability of such peptides for vaccination of melanoma patients, we tested whether DC are transfectable with eukaryotic expression plasmids. DC transfected with two reporter genes (CAT, beta-galactosidase) using a liposome-based transfection technique, exhibited only low levels of enzymatically active proteins, but were able to degrade rapidly intracellular proteins and to process peptides efficiently. Chloramphenicol acetyltransferase as well as tyrosinase mRNA were detectable after transfection by reverse-transcriptase-polymerase chain reaction, and enzyme activities became measurable. Furthermore, DC transfected with the tyrosinase gene were able to induce specific T cell activation in vitro, indicating appropriate peptide processing and presentation in DC after transfection. These data suggest new approaches to future tumor vaccination strategies.

Vaccination with IL-12 gene-modified autologous melanoma cells: preclinical results and a first clinical phase I study.

Cytokine gene transfer into tumor cells has been shown to mediate tumor regression and antimetastatic effects in several animal models via immunomodulation. Therefore, clinical protocols have been developed to treat cancer patients with cytokine gene-modified tumor cells. We inserted the genes coding for the p35 and p40 chain of interleukin-12 (IL-12) in two independent eukaryotic expression vectors and transduced melanoma cells of 15 different primary tumor cultures with both plasmids by a ballistic gene transfer approach. Secreted IL-12 demonstrated strong bioactivity by inducing interferon-gamma release from peripheral blood lymphocytes upon coculture with cell culture supernatants after IL-12 gene transfer which could at least partly be blocked by IL-12-specific antisera. Further enrichment of transduced tumor cells by magnetic separation directly after gene transfer increased cytokine secretion from a mean of 119 pg in the unsorted to 507 pg IL-12 (24 h/10(8) cells) in the magnetically enriched cell fraction. Irradiation of these cells led to a further elevation of secreted IL-12 (mean 987 pg). Elevated IL-12 levels were detected over 7 days after irradiation in vitro. In a subsequent first clinical phase I study six patients with metastatic melanoma were vaccinated with autologous, interleukin-12 gene-modified tumor cells. Melanoma cells were expanded in vitro from surgically removed metastases, transduced by ballistic gene transfer, irradiated and were then injected subcutaneously (s.c.) at weekly intervals. Clinically, there was no major toxicity except for mild fever. All patients completed more than four s.c. vaccinations over 6 weeks and were eligible for immunological evaluation. Post-vaccination, peripheral mononuclear cells were found to contain an increased number of tumor-reactive proliferative as well as cytolytic cells as determined by a limiting dilution analysis in two patients. Two patients developed DTH reactivity against autologous melanoma cells and one had a minor clinical response. Biopsies taken from that patient's metastases revealed a heavy infiltration of CD4+ and CD8+ T lymphocytes. In conclusion, vaccination induced immunological changes even in a group of advanced, terminally ill patients. These changes can be interpreted as an increased antitumor immune response.

Metastatic potential of human melanoma cells in nude mice--characterisation of phenotype, cytokine secretion and tumour-associated antigens.

Incidence and mortality of human malignant melanoma has risen rapidly over recent decades. Although the notorious resistance to treatment is characteristic for metastatic malignant melanoma, only a few experimental models have been established to study the metastatic cascade or to test new alternative treatment modalities. Thus, new human models are wanted. Here, we describe the metastatic behaviour of seven human melanoma cell lines derived from two primary cutaneous melanomas (WM 98-1, WM 1341) and five metastases established from liver (UKRV-Mel-4), skin (M7, M13), pleural effusion (UKRV-Mel-2) and lymph node (MV3). All cell lines were analysed for their capacity to grow in nude mice after s.c. and i.v. administration. M13 cells developed liver metastases spontaneously after s.c. injection, and subsequent passages of M13 and M7 melanoma cells caused liver metastases after i.v. injection, whereas MV3 and WM98-1 gave rise to lung metastases, using the same inoculation route. In contrast, WM 1341, UKRV-Mel-2 and UKRV-Mel-4 grew only very slowly in nude mice after s.c. injection and did not cause any metastases after i.v. or s.c. administration. The pattern of metastases or growth kinetics did not correlate with the interleukin 8 or tumour necrosis factor secretion of cell lines. Adhesion molecules and growth factor receptor expression on the cell lines differed widely, as determined by flow cytometry, with the low metastatic cell lines (UKRV-Mel-2, UKRV-Mel-4 and WM 1341) demonstrating a marked reduction in VLA-1 and VLA-5 expression compared with the metastatic lines (M7, M13, MV3 and WM 98-1). Expression of pigment-related proteins such as tyrosinase, TRP-1, TRP-2, Melan-A/MART-1, gp100, MAGE1 or MAGE-3 was not associated with growth and metastatic characteristics of the melanoma cell lines analysed. In conclusion, the established human melanoma cell lines exhibited diverse growth behaviour in nude mice in congruence with some early established prognostic markers such as VLA-1 and VLA-5. The xenografts provide good models for further study of metastatic processes as well as for evaluation of alternative treatment modalities including new pharmaceutical drugs and gene therapeutic targeting using tissue-specific gene regulatory elements for gene targeting.

Vaccination with IL-7 gene-modified autologous melanoma cells can enhance the anti-melanoma lytic activity in peripheral blood of patients with a good clinical performance status: a clinical phase I study.

Recently, cytokine gene transfer into tumour cells has been shown to mediate tumour regression in animal models via immunomodulation. Consequently, a number of clinical protocols have been developed to treat cancer patients with cytokine gene-modified tumour cells. Here, we report the results of a clinical phase I trial using for the first time autologous, interleukin 7 gene-modified tumour cells for vaccination of ten patients with disseminated malignant melanoma. Melanoma cells were expanded in vitro from surgically removed metastases, transduced by a ballistic gene transfer technique and were then injected after in vitro irradiation s.c. at weekly intervals. Clinically, there was no major toxicity except for mild fever, and no major clinical response towards vaccination was observed. Eight of ten patients completed the initial three s.c. vaccinations and were eligible for immunological evaluation. Post vaccination, peripheral mononuclear cells (PBMCs) were found to contain an increased number of tumour-reactive proliferative as well as cytolytic cells, as determined by a limiting dilution analysis. In three of six patients, the frequencies of anti-melanoma cytolytic precursor cells increased between 2.6- and 28-fold. Two of these patients showed a minor clinical response. Analysis of the autologous tumour cell vaccines regarding IL-7 secretion after gene transfer, HLA class I and class II cell surface expression, secretion of immunosuppressive mediators (TGF-beta1, IL-10) and various melanoma-associated tumour antigens revealed a very diverse expression profile. In conclusion, vaccination using gene-modified autologous melanoma cells induced immunological changes in a group of advanced, terminally ill patients. These changes can be interpreted as an increased anti-tumour immune response. However, immunological modulation was most pronounced in patients in good physical condition. Therefore, patients with minimal tumour load or minimal residual disease might preferentially benefit from tumour cell vaccination in further studies. In order to evaluate the effects of the cytokine gene-modified tumour cell vaccines more precisely, an antigenically better defined vaccine is needed.