PD-1 blockade improves the anti-tumor potency of exhausted CD3+CD56+ NKT-like cells in patients with primary hepatocellular carcinoma

CD3(+)CD56(+) NKT-like cells play pivotal roles in the anti-tumor immune defense response. However, little is known regarding circulating NKT-like cells in patients with primary hepatocellular carcinoma (HCC). In the present study, we demonstrate that circulating NKT-like cells in HCC patients are functionally impaired and anti-PD-1 blockade improves their anti-tumor potency. Circulating NKT cells were mainly comprised of CD8+ T cells. The frequencies and absolute counts of circulating NKT-like cells were comparable between HCC patents compared to healthy donors. NKT-like cells in HCC patients were impaired in their production of TNF-alpha and IFN-gamma as well as cytotoxicity. The level of activating receptor NKG2D was significantly decreased on NKT-like cells in HCC patients. In contrast, the expression of inhibitory receptors PD-1, Tim-3, and CTLA-4 were markedly increased on NKT-like cells in HCC patients. Meanwhile, the expression of PD-L1 was also upregulated on NKT-like cells in HCC patients. In detail, PD-1(+) NKT-like cells expressed lower levels of NKG2D, higher levels of Tim-3, and CTLA-4, and less IFN-gamma when compared with PD-1(-) NKT-like cells. Importantly, PD-1 blocked with anti-PD-1 antibody effectively improved the effector function of NKT-like cells from HCC patients or healthy donors. Our findings unveil the functional characterization of NKT-like cells in HCC patients and provide the potential targets to improve their function, which might benefit the optimization of HCC immunotherapy.