Long-chain acylcarnitines induce senescence of invariant natural killer T cells in hepatocellular carcinoma


 CD1d-restricted invariant natural killer T (iNKT) cells actively patrol the liver and possess valuable antitumor potential. However, clinical trials evaluating administration of iNKT cell-specific agonist α-galactosylceramide (α-GalCer) have failed to achieve obvious tumor regression. Improving the efficacy of iNKT cell-based immunotherapy requires a better understanding of the factors restraining the clinical benefits. In the context of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC), we found circulating and hepatic iNKT cells were hyperactivated but demonstrated imbalances in ratio and defective α-GalCer responsiveness. Exogenous interleukin-2 (IL-2) helped to expand residual α-GalCer responsive clones with reduced T cell receptor diversity. However, transcriptome-wide analysis revealed activation of the senescence-associated secretory phenotype and dampened cytotoxicity in iNKT cells, weakening their immune surveillance capacity. The senescent status of iNKT cells from the patients was further illustrated by cell cycle arrest, impaired telomere maintenance, perturbed calcium transport-related biological processes, and altered metabolism. Lipidomics profiling revealed the accumulation of long-chain acylcarnitines (LCACs) and aberrant lipid metabolism in HCC tissue. Exogenous LCACs, especially palmitoyl-carnitine (PC) and stearoyl-carnitine (SC), inhibited iNKT cell expansion and promoted senescence. Collectively, our results provide deeper insights into iNKT cell dysregulation and identify a cell senescence-associated challenge for iNKT cell-based immunotherapy in HBV-related HCC. The mechanistic links between iNKT cell senescence and accumulated LCACs suggest new targets for anti-HCC immunotherapies.