Abstract A091: Specific myelomonocytic cells heavily infiltrate orthotopic lung tumors and display a hypoxia-driven miRNA expression signature that directs tumor-supporting functions and negatively impacts on clinical outcome

Tumor-derived micro-RNA expression patterns are known to convey prognostic information in lung cancer. However, the cellular source of these signatures is unclear. In parallel, immunological parameters such as the presence and activation status of dendritic cells (DCs) emerge as important prognostic factors in this disease as well, presumably by affecting the quality of immune surveillance.We hypothesized that tumor-associated DCs are involved in the way tumor-derived miRNA expression patterns impact on disease outcome.Using a preclinical model of lung cancer featuring orthotopic tumor growth in syngeneic, immunocompetent hosts, we found that lung tumors were preferentially infiltrated by CD11c+/MHCII+/CD11b+/CD103- DCs (TIDCs). Compared to their peritumoral counterparts, displayed a dramatic overexpression of PD-L1 along with markers associated with tumor-associated macrophages (TAM). Transcriptome analysis of these CD11b+ TIDCs vs peritumoral CD11b+ DCs using GSEA and ISMARA indicated loss of immunogenicity, upregulation of features related to immunosuppressive TAMs, and exposure to hypoxia. Global miRNA profiling of CD11b+TIDCs revealed a specific signature dominated by a strong overexpression of mir-31, a prototypical lung cancer oncomir. Exposure to hypoxia appeared as a powerful driver of endogenous miR-31 expression in DCs. Confocal microscopy of intrapulmonary tumors confirmed that CD11c+ dendritic-shaped leukocytes colocalize within hypoxic regions. We found that miR-31 overexpression and hypoxia alike cause DCs to secrete the tumor-supporting factors VEGF, S100A8 and S100A9. Conditioned medium of miR-31-overexpression DCs induced pro-invasive cell morphology changes in lung carcinoma cells cultured on a collagen matrix, a phenomenon that could be reproduced by exposure to recombinant S100A8 protein. By re-processing TCGA expression data for non-coding RNA sequences, we discovered that the lung TIDC miRNA signature imparts a strong negative impact on overall survival in non-squamous lung cancer. Moreover, the TIDC-derived miRNA signature induced a profound difference in outcome among lung cancer patients with regional lymph node invasion.In summary, lung tumors predominantly recruit inflammatory-type DCs that are reprogrammed at the level of immuno-phenotype and micro-RNA repertoire. The miRNA signature of lung tumor-infiltrating DCs is dominated by the miR-31, a hypoxia-induced oncomir stimulating the release of pro-metastatic proteins by DCs. Finally, we show for the first time that a miRNA signature derived from a stromal immune cell has a dramatic impact on long term outcome in lung cancer. Citation Format: Elisabeth Brabants, Lotte Pyfferoen, Celine Everaert, Simon Tavernier, Kelly Heyns, Nancy De Cabooter, Glenn Wagemans, Kim Deswarte, Hamida Hammad, Olivier De Wever, Jo Vandesompele, Bart Lambrecht, Pieter Mestdagh, Karim Vermaelen. Specific myelomonocytic cells heavily infiltrate orthotopic lung tumors and display a hypoxia-driven miRNA expression signature that directs tumor-supporting functions and negatively impacts on clinical outcome [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr A091.