gms | German Medical Science

Objective: Squamous cell carcinoma of the head and neck (SCCHN) are able to change the phenotype and function of infiltrating dendritic cells (DC) dramatically. So far, little is known about the underlying mechanisms. A better knowledge of the phenotypic and functional characteristics as well as the distribution of DC in SCCHN, tumor draining lymph nodes and peripheral blood are essential to advance our understanding of the interaction between SCCHN and DC. This knowledge may lead to the development novel immunotherapeutic strategies.

Methods: Samples from the primary tumor, lymph nodes and peripheral blood where collected from patients with SCCHN undergoing tumor-surgery together with neck dissection. The samples were prepared for flow-cytometry by mechanical pulping, gradient centrifugation and enzymatic digestion using dnase and collagenase. Analyses were performed by 6-color-flow-cytometry (FacsCanto, Becton Dickinson). DC were itemized by labeling with CD123, lin-package, CD11c and anti-HLA-DR. Furthermore, the expression of co-stimulatory molecules such as CD40, CD80 and CD86 were investigated using the respective antibodies. For in vitro short-time cultures of tumor cells, blood cells or single cell suspensions from lymph nodes, cells were incubated with the CPG-oligonucleotide 2216 or with medium alone as a negative control.

Results: In patients with SCCHN, a significant reduction of plasmacytoid and myeloid DC was observed in the tumor tissue and the associated lymph nodes as compared to blood and tissue samples from healthy donors. The level of expression of co-stimulatory molecules was significantly reduced on DC found in the tumor or in tumor-affected lymph nodes. In vitro cultivation of DC together with CPG-oligonucleotides lead to an massive up-regulation of co-stimulatory molecules as compared to the negative control.

Conclusions: We have shown that SCCHN are able to change the phenotype of tumor infiltrating DC by a down-regulation of co-stimulatory molecules expressed on the surface to low levels. These molecules, that are normally expressed in high levels on mature and activated DC, are essential for the proliferation and activation of antigen-specific T-cells that could contribute to an effective anti-tumor immune response. Our results therefore imply, that the interaction between T-cells and DC is severely compromised. We could further show that the in vitro co-cultivation of immunostimulatory molecules with DC isolated from the tumorenvironment could reconstitute the expression of co-stimmulatory molecules. Further analysis of functional and phenotypic characteristics of DC in the tumor-micro-environment together with the ability to manipulate DC function for an enhanced antitumor immune response may support the development of future cancer therapies.