Alternatively activated plasmacytoid dendritic cells promote post-transplant hepatocellular carcinoma recurrence via adenosine A1 receptor

Abstract

Background: Alternatively-activated plasmacytoid dendritic cells (pDCs) can induce regulatory T cells (Treg) and facilitate tumor growth and metastasis. pDCs are generally abundant in liver and will be activated by hepatic ischemia-reperfusion injury. Extracellular accumulated adenosine in response to hypoxia or ischemia is a critical immunological regulator in innate and adaptive immunity. In this study, we aimed to investigate the role of pDCs on post-transplant HCC recurrence as well as its underlying mechanisms. Methods: The phenotypes of pDCs in clinical samples and rat orthotopic liver transplantation model were analyzed by flow cytometry and immunohistochemistry. The recruitment of pDCs was assessed by 3D hanging drop co-culture in vitro, and the direct role of pDCs on HCC was investigated by mouse HCC models in vivo. The transcriptional regulation of ecto-nucleotidases CD39 and CD73 was investigated by ChIP assay. Results: Clinically, the frequency of intra-graft pDCs was increased significantly after LT (Fig. 1A), and recipients with HCC recurrence had more intra-graft pDCs compared with those without recurrence (Fig. 1B). The depletion of pDCs attenuated tumor growth by decreasing CD4+ Foxp3+ Treg cells and increasing CD8+ T cells in mice after hepatic I/R injury with major hepatectomy (Fig. 2). Hypoxia promoted the migration of pDCs through adenosine A1 receptor (A1R) (Fig. 3A). Adenosine promoted the expression of IDO and ICOSL on pDCs, and adenosine-activated pDCs substantially enhanced the differentiation of naive T cells into Treg cells in vitro (Fig. 3B). The up-regulated intra-graft expression of ecto-nucleotidases CD39 and CD73 were found in recipients with HCC recurrence (Fig. 4A). CD39 and CD73 were potential targets of HIF1a and HIF2a (Fig. 4B). Conclusion: Adenosine/A1R signaling recruited and alternatively activated pDCs, which subsequently promoted HCC recurrence after LT. Targeting pDCs could be potential immunotherapy for HCC.