Gene expression profiling of mature dendritic cells from mice s. c. treated with GM-CSF-gene transduced LLC cells (LLC/SeV/GM) or control cells (LLC, LLC/SeV/GFP). Mus musculus

Irradiated granulocyte macrophage-colony stimulating factor (GM-CSF)-transduced autologous tumor cells induce substantial antitumor immunity through the maturation and migration of dendritic cells (DCs). However, little is known about the key molecules involved in GM-CSF-sensitized DCs (GM-DCs) in tumor draining lymph nodes (TDLNs). We initially confirmed that mice subcutaneously injected with poorly immunogenic syngeneic Lewis lung carcinoma (LLC) cells transduced with Sendai virus encoding GM-CSF (LLC/SeV/GM) significantly rejected the tumor growth. Using microarray expression profiling, we obtained a large number of gene expression data files from GM-DCs and control DCs in TDLNs, and subjected them to network-based cluster analysis and unexpectedly unraveled the expression levels of type I IFNs-related genes specifically expressed in plasmacytoid DCs (pDC) were robustly up-regulated in GM-DCs. In vivo depletion assay showed that pDC-depleted mice treated with subcutaneous LLC/SeV/GM cells abrogated the antitumor effects observed in control mice. Moreover combination use of imiquimod for TLR7 triggering on pDC with irradiated LLC/SeV/GM cells induced a significant therapeutic antitumor effect with marked induction of CD9+ pDC with antitumor phenotype, whereas other control mice groups had only minimal to-modest antitumor responses, implicating that this combined vaccine strategy using imiquimod could be promising for improvement of GM-CSF-induced antitumor immunity. Overall design: Mouse GM-CSF induced gene expression in mature dendritic cells in tumor draining lymph nodes from C57/BL6N female mouse was measured at 2 days after s.c. tumor challenge with GM-CSF gene-transduced LLC cells (LLC/SeV/GM) or control cells (LLC, LLC/SeV/GFP).