Dendritic cells for the immunotherapy of renal cell carcinoma.
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Carcinoma, Renal Cell↗
Biomedical subjects
R Ramoner
Publications and source records attributed to R Ramoner.
In vitro generation of CD83+ human blood dendritic cells for active tumor immunotherapy.
There is increasing clinical interest in dendritic cells that are capable of initiating antitumor immune responses. Dendritic cells cultured from human blood mononuclear cells using granulocyte/macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4) are competent for antigen uptake but express relatively low levels of costimulatory molecules and thus correspond to immature resident tissue dendritic cells. In this study we took advantage of the new dendritic cell-specific marker CD83, which is expressed by mature dendritic cells, to delineate the maturation of cultured human blood dendritic cells. Although dendritic cells cultured with GM-CSF and IL-4 contained transcripts for CD83 as determined by reverse transcription PCR, CD83 protein was barely detectable by flow cytometry, confirming that dendritic cells obtained with this system are immature. However, treatment of dendritic cells with tumor necrosis factor-alpha (TNF-alpha) significantly increased the levels of CD83 transcripts and induced CD83 protein expression in dendritic cells. In contrast to the initiation of dendritic cell culture, which was facilitated by high cell density (5 x 10(6) cells/mL), differentiation into CD83+ dendritic cells required a low cell concentration (0.5 x 10(6) cells/mL). At higher cell density (1 x 10(6) cells/mL), CD83 expression was suppressed and was almost completely prevented at 2 x 10(6) cells/mL. Induction of CD83 expression was accompanied by a strong upregulation of the costimulator B7-2 (CD86) on dendritic cells. While untreated CD83(-) dendritic cells efficiently internalized fluoresceinated Dextran, TNF-alpha treated CD83+ dendritic cells excluded these molecules, confirming that maturation of dendritic cells was associated with the silencing of the antigen-capturing machinery. Morphologically, CD83+ dendritic cells presented with pronounced cytoplasmic projections (veils) characteristic of mature dendritic cells. In summary, we show that cell density critically regulates dendritic cell development. Knowledge of the appropriate conditions for dendritic cell generation and maturation will be important in clinical immunotherapy settings.
Antigens, CD↗
Human renal-cell carcinoma tissue contains dendritic cells.
Immune surveillance of cancer requires antigen-presenting cells which activate T cells specific for tumor-associated antigens. We show here that substantial numbers of dendritic cells, which are the most potent antigen-presenting cells, emigrate from renal-tumor explants in organ culture. Tumor-derived dendritic cells presented with all characteristics of mature dendritic cells. Dendritic cells could be identified by typical cytoplasmic projections (=veils). They expressed high levels of MHC products and of the co-stimulator CD86 (B7-2). Dendritic cells expressed the CD45RO isoform but not CD45RA. The most important point was that up to 9% of the emigrating leukocytes expressed the CD83 antigen, a specific marker for mature dendritic cells. CD83+ cells were approximately 40-fold enriched in the tumor tissue as compared to the peripheral blood. In contrast to cultured blood dendritic cells, tumor-emigrant dendritic cells had a reduced potential to capture soluble antigen, as shown by the exclusion of fluoresceinated Dextran molecules. Finally, in mixed leukocyte reactions, tumor-derived dendritic cells were able to stimulate naive T cells from cord blood, which is a unique feature of dendritic cells. This study demonstrates that genuine dendritic cells reside in or infiltrate renal-cell carcinoma tissue. The failure of patients with renal-cell carcinoma to mount an anti-tumor immune response despite the presence of professional antigen-presenting cells in the tumor tissue suggests that tumor-associated dendritic cells are suppressed in situ, in a similar way to that described for tumor-infiltrating lymphocytes.
Antigens, CD↗