Development of a new protocol for 2-day generation of mature dendritic cells from human monocytes

We developed a new 2-day protocol for the generation of dendritic cells (DCs) from human monocytes in vitro. First, we demonstrated that 24 hours of culture with GM-CSF and IL-4 are sufficient to generate immature DCs capable of antigen uptake. We then compared two different strategies for DC maturation: proinflammatory mediators were either added together with GM-CSF and IL-4 from the beginning of cell culture or added after 24 hours of differentiation with GM-CSF and IL-4. After 48 hours of total culture period, expression of activation markers was more pronounced in cells generated by the 2-step differentiation and activation method. Our new protocol for 2-day DC differentiation reduces labor, cost and time and also reliably renders high numbers of mature and viable DCs.

FastDC derived from human monocytes within 48 h effectively prime tumor antigen-specific cytotoxic T cells

Previously, we have shown that dendritic cells (DCs) with full T-cell stimulatory capacity can be derived from human monocytes after 48 h of in vitro culture (FastDC). Compared to a standard 7-day protocol, this new strategy not only reduces the time span and the amount of recombinant cytokines required, but may also resemble DC development in vivo more closely. Using a melanoma antigen model, we show here that FastDC prime CTL responses against tumor antigens as effectively as standard monocyte-derived DCs (moDCs). FastDC and moDCs derived from monocytes of HLA-A2(+) donors were loaded with the melanoma-associated, HLA-A(*)0201-restricted peptide Melan-A and cocultured with autologous CD3(+) T cells. After two weekly restimulations with freshly prepared, peptide-loaded FastDC or moDCs, binding of CD8(+) T cells to fluorescently labeled MHC-I/Melan-A-peptide complexes and intracellular cytokine staining revealed that the two DC preparations had an equal capacity to prime Melan-A-specific, IFN-gamma producing CD8(+) T cells. CTLs derived from cocultures with FastDC lysed Melan-A-loaded T2 cells even more effectively than CTLs primed by moDCs. Comparative analysis also revealed that FastDC possess an equal capacity to migrate in response to the chemokine receptor CCR-7 ligand 6Ckine. Importantly, DCs can be generated with higher yield and purity using the FastDC-protocol. The reliability and efficacy of this new strategy for DC development from monocytes may facilitate clinical investigation of DC-based tumor immunotherapy.

IFN- promotes definitive maturation of dendritic cells generated by short-term culture of monocytes with GM-CSF and IL-4

Dendritic cells (DC) generated in vitro have to be viable and phenotypically mature to be capable of inducing T cell-mediated immunity after in vivo administration. To facilitate optimization of DC-based vaccination protocols, we investigated whether the cytokine environment and the mode of activation affect maturation and survival of DC derived from monocytes by a short-term protocol. Monocytes cultured for 24 h with granulocyte macrophage-colony stimulating factor and interleukin-4 were stimulated with proinflammatory mediators for another 36 h to generate mature DC. Additional activation with CD40 ligand and interferon (IFN)-gamma increased viability of DC and promoted definitive maturation as defined by maintenance of a mature phenotype after withdrawal of cytokines. Addition of IFN-alpha to DC cultures prior to stimulation further enhanced definitive maturation: IFN-alpha-primed DC expressed high levels of costimulatory molecules and CC chemokine receptor 7 (CCR7) up to 5 days after cytokine withdrawal. Compared with unprimed DC, IFN-alpha-primed DC displayed equal capacity to migrate upon CCR7 ligation and to prime antigen-specific T helper cell as well as cytolytic T cell responses. In conclusion, we show that optimal maturation and survival of monocyte-derived DC require multiple activation signals. Furthermore, we identified a novel role for IFN-alpha in DC development: IFN-alpha priming of monocytes promotes definitive maturation of DC upon activation.

Chemosensitization of Pancreatic Carcinoma Cells to Enhance T Cell-Mediated Cytotoxicity Induced by Tumor Lysate-Pulsed Dendritic Cells

Dendritic cells (DCs) can induce cytotoxic T-cell (CTL) responses against tumor antigens in vitro and in vivo, yet few cancer patients experience tumor regression after DC-based vaccination. Combination with other treatment modalities, such as radiation or pharmacologic anticancer agents, may reduce tumor cell resistance against immune responses. The authors tested whether treatment with gemcitabine or cyclooxygenase-2 (COX-2) inhibitors increases the sensitivity of pancreatic carcinoma cells to CTL-mediated killing. Monocyte-derived DCs of HLA-A2+ donors were loaded with lysate from the HLA-A2+ pancreatic carcinoma cell line Panc-1 and co-cultured with autologous CD3+ T cells. ELISPOT and cytotoxicity assays performed after two rounds of in vitro stimulation confirmed induction of a tumor-specific CTL response. Changes in the magnitude and the effector mechanism of the CTL response were analyzed after treatment of Panc-1 cells with gemcitabine and COX-2 inhibitors. Compared with gemcitabine, COX-2 inhibitors more effectively sensitized Panc-1 cells to CTL-mediated killing and showed less inhibition of T-cell activation by DCs in vitro. Using anti-CD95 blocking antibody, the authors showed that the increase in CTL-mediated tumor cell killing observed after treatment with COX-2 inhibitors is dependent on CD95/CD95 ligand interaction. Increased apoptosis of Panc-1 cells treated with COX-2 inhibitor was also observed after incubation with agonistic anti-CD95 antibody. Sensitization of cancer cells to CD95-dependent killing by CTLs represents a novel mechanism of action for COX-2 inhibitors and provides a rationale for their concomitant use with immunotherapeutic strategies such as DC-based vaccination.

Noncontact detection of ocular melanoma with L-3-123I-iodo-alpha-methyltyrosine: first clinical results

The results of the first clinical trial are presented of the newly designed tumor-seeking radiopharmaceutical L-3-123I-iodo-alpha-methyltyrosine (IMT) for noncontact detection of malignant eye melanoma by means of a nuclear medicine technique. Eye scintigraphy (ES) was performed on ten outpatients clinically suspected of harboring an intraocular melanoma. ES was carried out with a twin pinhole eye collimator attached to a high resolution gamma camera; 7-10 mCi of IMT was given intravenously to each patient 100-150 min prior to the nuclear medicine investigation. Gamma camera eye scintigraphy and the use of IMT offer a useful noninvasive alternative to the radiophosphorus uptake test. Of the ten patients, five were found not to have a melanoma either clinically or by scintigraphy, three had a melanoma by scintigraphy that was confirmed histologically, and two yielded inconclusive results.

[Are 0.1% timolol-maleate eyedrops suitable for treating chronic glaucoma? (author's transl)]

On the basis of 47 patients with chronic open-angle glaucoma, the administration of 0.1% timolol-maleate eye-drops was investigated in the form of a controlled long-term study over a period of 56 weeks. It was found that in a remarkable proportion of chronic glaucoma cases, this low concentration had an adequate, long-term effect, reducing IOP by 24-27%. The results obtained give sufficient grounds for the assumption that in the initial stages of glaucoma, the 0.1% solution is just as effective as solutions of a higher concentration, provided that a satisfactory degree of responsiveness to timolol-maleate is present from the outset. The local and systemic side-effects are relatively slight and therefore also fewer than with higher concentrations. Since in over 50% of patients with chronic glaucoma, 0.1% timolol-maleate eye-drops reduce IOP adequately over a considerable period of time, the 0.1% solution is to be recommended at all events for the initial treatment of glaucoma patients.

[Nuclear medicine demonstration of intraocular tumors using gamma-radiating radionuclides. 1st clinical results]

A non-invasive method of detecting intraocular mass lesions is described which uses 67gallium citrate and 99m-technetium pertechnetate. It was used in 33 cases. In 73.7% of the patients with malignant melanoma of the eye there was a significant increase in the storage of the tracer. There was no difference in the results obtained with 67gallium citrate and 99m-technetium pertechnetate. Small, flat and peripheral tumors may not be detected. In some cases old intraocular hemorrhages may also lead to false-positive results. In contrast to the 32P-test the method described can be used in cases with opaque media. The radiation dose is about one-tenth of that given with the 32P-test.