*Purpose: Tumor recurrence is the main limitation of liver transplantation (LT) in patients with hepatocellular carcinoma (HCC). We previously reported an adoptive immunotherapy approach that uses liver-resident natural killer (lr-NK) cells derived from donor liver graft perfusate to prevent tumor recurrence after LT. In mice models, we also reported that TNF-related apoptosis-inducing ligand (TRAIL) expression in lr-NK cells decreases markedly after hepatectomy; however, the mechanism remains unknown. In this study, we focused on the aryl hydrocarbon receptor (AhR) as a factor to maintain TRAIL activity. AhR is known to be a transcription factor modulated by exogenous and endogenous ligands play important roles in the homeostasis of NK cells. AhR-/-mice have small number of TRAIL⁺lr-NK cells in the liver. Therefore, we assessed the role of the AhR signaling in lr-NK cells after partial hepatectomy.

*Methods: To investigate the effect of AhR signaling using AhR agonist; 6-formylindolo[3,2-b] carbazole (FICZ) on lr-NK cells after hepatectomy, FICZ was administered to the 70% hepatectomized C57BL/6J (B6) (H-2b) mice. Lr-NK cells were co-cultured with FICZ in the presence of IL-2 to analyze the phenotype and cytotoxic activities of lr-NK cells.

*Results: The administration of FICZ to wild B6 mice significantly increased the TRAIL expression on lr-NK cells compared to vehicle control group (33.7% vs 23.7%, respectively; p=0.011). Regarding the antitumor activities, the intravenous administration of FICZ increased the cytotoxicity of liver mononuclear cells (LMNCs) (E:T=40:1; 22.7%), compared with 10.0% of control group (p=0.001) on day 3 by⁵¹Cr release assay. Three days after 70% hepatectomy, the TRAIL expression of lr-NK cells significantly decreased to 1.6% from 23.7% (p=0.001). However, FICZ administration before hepatectomy markedly prevented the decreased TRAIL expression of lr-NK cells compared to vehicle control administration group (10.0% vs 1.6%; p=0.020). Furthermore, the addition of FICZ to the culture of LMNCs during 3 days in the presence of IL-2 significantly increased the ratio of lr-NK cells (11.6% vs 9.4%; p=0.002) and the TRAIL expression (27.6% vs 19.6%; p=0.027) compared with control vehicle group.

*Conclusions: AhR signaling using FICZ administration could maintain the TRAIL expression of lr-NK cells even after partial hepatectomy. Our observations that lr-NK cells require AhR for increase TRAIL expression introduce anti-tumor effect in the liver. These findings extend our knowledge of the factors contributing to HCC recurrence after LT.

« Back to 2020 American Transplant Congress