Abstract 451: Smad2 is the TGF-β receptor-regulated Smad to suppress the immunogenicity of mouse and human dendritic cells.

TGF-β plays pivotal roles in the regulation of DCs. However, the molecular mechanisms by which TGF-β regulates DCs are undetermined. Here, we show that one of the TGF-β receptor-regulated Smads (R-Smads), Smad2 is the predominant intermediary for TGF-β to suppress the immunogenicity of DCs. Notably, Smad2 remained expressed, whereas Smad3 was down-regulated in mouse BM-derived DCs (BMDCs) and human monocyte-derived DCs (MoDCs) upon differentiation by GM-CSF and IL-4. Smad2 mediated the inhibitory effect of TGF-β on the expression of co-stimulatory molecules (CD80, CD86, CD40) on BMDCs. One of the TGF-β superfamily cytokines, Activin-A did not affect their expression, although it shares Smad2 and Smad3 as R-Smads. Deletion of Smad2 up-regulated the dendrite formation, co-stimulatory molecule expression, and effector cytokine production by DCs, thereby efficiently activating allogeneic T cells. Furthermore, DC-specific deletion of Smad2 by Cd11cCre-loxP system suppressed the progression of a mouse EL4 lymphoma model by enhancing anti-lymphoma cytotoxic activity. Thus, our results suggest that TGF-β signaling through Smad2 in DCs could be a therapeutic target to enhance anti-tumor immunity. Citation Format: Jeong-Hwan Yoon, Jin-Soo Han, Seok Hee Park, Michael Weinstein, Susumu Nakae, Tadashi Yamashita, In-Kyu Lee, Takayuki Sumida, Katsuko Sudo, Masahiko Kuroda, Mizuko Mamura. Smad2 is the TGF-β receptor-regulated Smad to suppress the immunogenicity of mouse and human dendritic cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 451. doi:10.1158/1538-7445.AM2013-451