Abstract LB-114: The roles of COX-2 inhibitor in regulatory T cells and Th17 cells’ tumor immune regulation

Background: COX-2 and its metabolite, PGE2, affect tumorigenesis and tumor-induced immune suppression. In the field of tumor immunology, regulatory T cells (Tregs) and Th17 cells are emerging as important targets. The presence of Tregs might be important for inducing T-cell suppression and thus allowing tumor growth. Th17 cells play an active role in inflammation and autoimmune diseases. These cell types have reciprocal roles in inflammatory conditions. However, very little is known about the roles of the COX-2 inhibitor in Tregs and Th17 cells in tumor development. Therefore, we investigated the effects of COX-2 inhibitors on Treg and Th17 cell activation in a tumor model. Methods: In vitro assay, to evaluate the effects of COX-2 on the proliferation of Tregs and Th17 cells, CD4+CD62L+ naive T cells were incubated in the presence of TGF-s, with or without IL-6, and PGE2 or a COX-2 inhibitor (celecoxib) was then added. Through Western blotting, we assessed Foxp3 and the transcription factor retinoic acid-related orphan receptor (ROR)-, which were recently described essential for differentiation of Tregs and Th17 cells, respectively. In vivo assay, twenty mice were randomized into a group of normal control, Lewis lung cancer cells (3LL) inoculated control, and celecoxib 10 or 100mg/kg/day treated 3LL inoculated mice groups. The tumor mass and spleen of each mouse were removed for isolation of splenocytes and tumor infiltrating lymphocytes (TIL) for FACS analysis, real time PCR and Western blotting. Results: When CD4+CD62L+ naive T cells were stimulated under Treg-promoting condition (TFG-s only), the expression of Foxp3 increased. When naive T cells were stimulated under Th17-promoting conditions, TGF-s and IL-6 induced significant ROR- expression and IL-17 secretion. When naive T cells were treated with PGE2 and TGF-s, the expression of Foxp3 increased. These increased expressions were decreased in the presence of celecoxib. We assessed the effects of COX-2 on IL-17 production in TGF-s- and IL-6-stimulated naive T cells. We found that IL-17 production was increased with PGE 2 and decreased with celecoxib treatment, in a dose-dependent manner. The expressions of Foxp3 and ROR-γ in the tumor mass were decreased in the celecoxib treated mice groups. FACS analysis demonstrated a decline in the percentage of CD4 + IL17 + and CD4 + CD25 + in the celecoxib treated groups. Conclusion : The results of this study show that PGE2 increases the differentiation of Tregs and Th17 cells, while a COX-2 inhibitor inhibits the differentiation of both Tregs and Th17 cells. Although Tregs and Th17 cells have reciprocal roles, the COX-2 inhibitor decreases the differentiation of both Treg and Th17 cells. This mode of immunoregulatory action by a COX-2 inhibitor requires further investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-114.