Abstract C73: Dendritic cell-carcinoma interactions and the impact on their chemokine receptor expression and migration
Authors: Ramanathapuram Lalitha , Lamb Eldon , Kurago Zoya 
Published: May 2012

Previous studies of head and neck squamous cell carcinoma (HNSCC) samples in our laboratory have often shown numerous dendritic cells (DC) and their precursors throughout the tumor parenchyma and stroma and in contact with HNSCC cells in both primary tumors and their lymph node metastases. We hypothesized that monocytes and DC contribute to the pathogenesis of HNSCC. Preliminary long-term video-microscopic experiments with co-cultures of HNSCC cell lines and monocyte-derived DC revealed that DC can physically interact with HNSCC cells and can influence their directional migration. The directional migration of leukocytes, including DC, is regulated by chemokines. For example, when immature DC in the periphery are exposed to microbial products or certain cytokines, they begin maturation and up-regulate chemokine receptors CCR7 and CXCR4. While the role of CXCR4 in DC biology is not fully understood, CCR7 is important for DC migration to the lymph nodes in response to chemokines CCL19 and CCL21. Chemokines may also regulate cancer cell migration, as the expression of CXCR4 and CCR7 in several cancers was reported to correlate with lymph node metastases and poor prognosis. However, the mechanisms of chemokine receptor regulation and function in HNSCC are not understood.

Our current studies examine the potential impact of interactions of monocyte-derived DC with HNSCC on their migratory abilities. Monocytes are precursors of mucosal DC, so we purified peripheral blood monocytes and cultured them for 6 days with GM-CSF and IL-4 to produce fully differentiated immature DC (D6DC, non-adherent subset) and incompletely differentiated cells (moDC, adherent subset). MoDC and D6DC were then cocultured with a HNSCC cell line (SCC) or with normal primary oral keratinocytes (POK) for 3 days, and all co-cultures produced both floating and attached populations. All populations were analyzed for viability, chemokine receptor expression, morphology and ability to re-establish colonies. Remarkably, in contrast to SCC cells cultured alone, 25% of floating SCC cells in co-cultures with moDC or with D6DC were viable, as determined by flow cytometry with EpCam and activated caspase 3 labeling.

Immunohistochemistry for cytokeratins of re-plated floating moDC/SCC and D6DC/SCC populations revealed that the vast majority of SCC cells were bound to DC. SCC cells also influenced the DC phenotype, especially the less differentiated moDC, and induced approximately 8-fold increase in the number of CCR7-positive DC as well as CD38 expression. This is important, because CD38 is required for CCR7 function. In contrast to DC/SCC co-cultures, no viable floating POK cells were detected in the DC/POK co-cultures, and most DC were attached to the adherent POK. Similar to DC/SCC, DC/POK co-cultures induced CCR7 expression on moDC. Together, these results suggest that in vitro, moDC and D6DC may support the survival of detached (floating) SCC cells, possibly via cell-cell adhesion, as well as develop a migratory phenotype that could potentially lead DC to the lymph nodes. The migratory abilities of DC and SCC cells and the functional significance of SCC cells attached to CCR7-positive DC are under investigation.

Citation Information: Cancer Res 2009;69(23 Suppl):C73.