Jeong-Hwan Yoon

Phosphorylation status determines the opposing functions of Smad2/Smad3 as STAT3 cofactors in TH17 differentiation

Transforming growth factor-β (TGF-β) and interleukin-6 (IL-6) are the pivotal cytokines to induce IL-17-producing CD4+ T helper cells (TH17); yet their signalling network remains largely unknown. Here we show that the highly homologous TGF-β receptor-regulated Smads (R-Smads): Smad2 and Smad3 oppositely modify STAT3-induced transcription of IL-17A and retinoic acid receptor-related orphan nuclear receptor, RORγt encoded by Rorc, by acting as a co-activator and co-repressor of STAT3, respectively. Smad2 linker phosphorylated by extracellular signal-regulated kinase (ERK) at the serine 255 residue interacts with STAT3 and p300 to transactivate, whereas carboxy-terminal unphosphorylated Smad3 interacts with STAT3 and protein inhibitor of activated STAT3 (PIAS3) to repress the Rorc and Il17a genes. Our work uncovers carboxy-terminal phosphorylation-independent noncanonical R-Smad–STAT3 signalling network in TH17 differentiation.

Proangiogenic TIE2+/CD31+ macrophages are the predominant population of tumor-associated macrophages infiltrating metastatic lymph nodes

Tumor-associated macrophages (TAMs) accumulate in various cancers and promote tumor angiogenesis and metastasis, and thus may be ideal targets for the clinical diagnosis of tumor metastasis with high specificity. However, there are few specific markers to distinguish between TAMs and normal or inflammatory macrophages. Here, we show that TAMs localize in green fluorescent protein-labeled tumors of metastatic lymph nodes (MLNs) from B16F1 melanoma cells but not in necrotic tumor regions, suggesting that TAMs may promote the growth of tumor cells and the progression of tumor metastasis. Furthermore, we isolated pure populations of TAMs from MLNs and characterized their gene expression signatures compared to peritoneal macrophages (PMs), and found that TAMs significantly overexpress immunosuppressive cytokines such as IL-4, IL-10, and TGF-β as well as proangiogenic factors such as VEGF, TIE2, and CD31. Notably, immunological analysis revealed that TIE2+/CD31+ macrophages constitute the predominant population of TAMs that infiltrate MLNs, distinct from tissue or inflammatory macrophages. Importantly, these TIE2+/CD31+ macrophages also heavily infiltrated MLNs from human breast cancer biopsies but not reactive hyperplastic LNs. Thus, TIE2+/ CD31+ macrophages may be a unique histopathological biomarker for detecting metastasis in clinical diagnosis, and a novel and promising target for TAM-specific cancer therapy.

Activin receptor‐like kinase5 inhibition suppresses mouse melanoma by ubiquitin degradation of Smad4, thereby derepressing eomesodermin in cytotoxic T lymphocytes

Varieties of transforming growth factor-b (TGF-b) antagonists have been developed to intervene with excessive TGF-b signalling activity in cancer. Activin receptor-like kinase5 (ALK5) inhibitors antagonize TGF-b signalling by blocking TGF-b receptor-activated Smad (R-Smad) phosphorylation. Here we report the novel mechanisms how ALK5 inhibitors exert a therapeutic effect on a mouse B16 melanoma model. Oral treatment with a novel ALK5 inhibitor, EW-7197 (2.5 mg/kg daily) or a representative ALK5 inhibitor, LY-2157299 (75 mg/kg bid) suppressed the progression of melanoma with enhanced cytotoxic T-lymphocyte (CTL) responses. Notably, ALK5 inhibitors not only blocked R-Smad phosphoryla-tion, but also induced ubiquitin-mediated degradation of the common Smad, Smad4 mainly in CD8 þ T cells in melanoma-bearing mice. Accordingly, T-cell-specific deletion of Smad4 was sufficient to suppress the progression of melanoma. We further identified eomesodermin (Eomes), the T-box transcription factor regulating CTL functions, as a specific target repressed by TGF-b via Smad4 and Smad3 in CD8 þ T cells. Thus, ALK5 inhibition enhances anti-melanoma CTL responses through ubiquitin-mediated degradation of Smad4 in addition to the direct inhibitory effect on R-Smad phosphorylation. OPEN ACCESS TRANSPARENT PROCESS SOURCE DATA ALK5 inhibitors degrade Smad4 to derepress CTLs 1720 ß 2013 The Authors. Published by John Wiley and Sons, Ltd on behalf of EMBO. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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