Epidermal expression of oncogenic ras subverts cytotoxic inflammation by skewing infiltrating myeloid cells towards an immunosuppressive phenotype. (100.16)

Abstract

Abstract Cancer development is frequently accompanied by inflammation and immune activation. The nature of this inflammatory response, however, is non-uniform and can consist of cells with opposing functions. To characterize the innate immune response to neoplastic epithelial tissue, we used an epidermally-restricted transgenic mouse model of oncogenic H-Ras expression in which epidermal hyperplasia and premalignant progression induces aberrant myelopoesis and cutaneous hyperinflammation associated with the formation of myeloid resident epithelial microabscesses. Antibody mediated depletion of neutrophils concurrent with transgene activation ablated neutrophil infiltration and microabscesses resulting in increased epidermal thickening relative to isotype controls. Neutrophils isolated from mice expressing ras for 1 week killed keratinocytes in vitro, suggesting that the in vivo myeloid response to oncogenic ras expression is initially a cytotoxic one. Simultaneously, there is cutaneous upregulation of genes implicated in the activation, function and recruitment of myeloid derived suppressor cells (MDSC) such as GMCSF, GCSF, MMP9, VEGF, S100A8/9, CCL2, and IL1β. This coincides with upregulation of IL4Rα on myelocytes, increased percentage of Tregs, and decreased effector T cell responses from 1 to 2 weeks post H-Ras expression. These data suggest that the acute cytotoxic neutrophil response is replaced by a suppressor myeloid phenotype that could enhance neoplastic progression.