Abstract 922: PGE2/HuR/CEBPD axis in macrophages contributes to immunosuppression and inhibits phagocytosisof nasopharyngeal carcinoma

The association of inflammation and cancer progression via modulation of phagocytosis and suppression of adaptive immunity by tumor-associated macrophages (TAM) to promote tumorigenesis has been implicated in a number of recent studies. To date, the underlying mechanisms involving the interactions of these two cellular processes remain elusive, particularly in the involvement of posttranscriptional regulation. In this study, we demonstrate that prostaglandin E2 (PGE2) activates transcription factor CCAAT/enhancer binding protein delta (CEBPD) in macrophages by inducing nucleocytoplasmic shuttling of RNA binding protein Hu antigen R (HuR), which plays a direct role in stabilizing CEBPD mRNA in macrophages. Increase of CEBPD resulted in elevated expression of IL-10, a well-studied immunosuppressor, and PTX3, which contribute to suppression of phagocytosis of cancer cells by macrophages. In addition, the conditioned medium of CEBPD-transfected macrophages showed an immunosuppressive effect to attenuate phagocytosis of cancer cells by macrophages, suggesting an autocrine mode of regulation. Immunohistochemistry studies demonstrated that the cytosolic level of HuR protein correlates with increased CEBPD in TAM and malignant nasopharyngeal carcinoma (NPC). Collectively, these results provide new evidences that the inflammatory PGE2/HuR/CEBPD axis in macrophages plays protumor roles in controlling immunosuppression and attenuating phagocytosis of cancer cells by macrophages. Citation Format: Yu-Wei Hsiao, Ju-Ming Wang. PGE2/HuR/CEBPD axis in macrophages contributes to immunosuppression and inhibits phagocytosisof nasopharyngeal carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 922.