HLA-E/NKG2A hampers tumor surveillance of natural killer cells induced by TLR4-mediated hepatic senescence

Abstract

<p><strong>Background</strong> Hepatocellular carcinoma (HCC) recurrence occurs at a rate of 10–20% within 5 years after Liver transplantation (LT). Graft injury during LT significantly affects tumor recurrence by immunological regulation. However, the role of natural killer (NK) cells in HCC recurrence was not understood.</p><p><strong>Methods</strong> 346 HCC patients who underwent LT were recruited. The correlation between NKG2A+NK cells and tumor recurrence was analyzed. The cytotoxic function of NKG2A+NK cells was evaluated by co-culture with HCC cells by LDH assay. Hepatic ischemia-reperfusion injury plus major hepatectomy (IRI+Hx) in C57bl/6 mice was established. Tumor cells (Hepa 1–6) were injected into the liver via the portal vein.</p><p><strong>Results</strong> GWR (the ratio of graft volume to estimated liver volume) < 60% was an independent risk factor for early tumour recurrence after LT (IDDF2022-ABS-0267 Figure 1). The frequencies of circulating and intra-graft NK cells were lower in GWR < 60% patients post-LT (IDDF2022-ABS-0267 Figure 2). NK cells in GWR < 60% patients expressed lower Granzyme B and IFN-γ, whereas higher inhibitory marker NKG2A (IDDF2022-ABS-0267 Figure 3A, IDDF2022-ABS-0267 Figure 3B), along with increased expressions of its ligand HLA-E and inflammatory signatures. HLA-E was significantly correlated with TLR4 (IDDF2022-ABS-0267 Figure 3C). The cytotoxic function of NKG2A+NK cells was significantly decreased as they expressed lower activating markers and decreased cytokines (IDDF2022-ABS-0267 Figure 4A). When co-cultured with HCC cells, NKG2A+NK cells were with less cytotoxicity (IDDF2022-ABS-0267 Figure 4B). In IRI+Hx mouse model, liver-resident NK cells shifted to liver infiltrated NK cells after IRI+Hx, with increased expressions of NKG2A on NK cells and hepatic HLA-E mRNA (IDDF2022-ABS-0267 Figure 5A). After tumor cell injection, NKG2A+ liver-resident NK cells were increased in IRI+Hx group compared to the controls (IDDF2022-ABS-0267 Figure 5B). Senescent hepatocytes were significantly induced after hepatic IRI+Hx (IDDF2022-ABS-0267 Figure 6A). Furtherly, upregulation of NKG2A on NK cells was induced by co-cultured with senescent hepatocytes (IDDF2022-ABS-0267 Figure 6B).</p>