Xiaohong Liang

Background: Natural killer (NK) cells act as the host’s first line of immunosurveillance, and their maturation and effector functions are finely regulated by multiple factors. Although histone deacetylase (HDAC) inhibition has been reported to impair NK cell viability and/or antitumor effects, the specific HDAC member involved and the underlying mechanisms remain unclear. Methods: We analyzed the expression of HDAC family members during NK cell activation and in tumor-infiltrating NK cells. Genetic approaches, including Hdac6 knockout, knockdown, and overexpression, were used to evaluate its role in NK cell proliferation, maturation, and effector function. Mechanistic studies examined protein acetylation status, chaperone activity, and IL-15–STAT5 signaling. Functional relevance was assessed using NK cell adoptive transfer models and interleukin (IL)-15 combination treatment in tumor settings. Results: HDAC6 was the most significantly upregulated HDAC member on NK cell activation, whereas its expression was reduced in tumor-infiltrating NK cells and correlated with poor patient survival. Hdac6 deficiency markedly impaired NK cell proliferation, maturation, and effector functions, while Hdac6 overexpression showed a promoting effect. Mechanistically, loss of Hdac6 led to the hyperacetylation of HSP90, which in turn destroyed its chaperone activity for phosphorylated STAT5 and blocked the transduction of the IL-15 signaling pathway indispensable for NK cell maturation and effector function. Translationally, HDAC6 overexpression not only obviously improved tumor suppression of transferred NK cells, but also synergized with IL-15 treatment to further boost NK cell antitumor efficacy. Conclusion: HDAC6 was identified as a critical regulator of NK cell biology through strengthening the IL-15/STAT5 pathway and may serve as a potential target for improving NK cell function.

Psychological stress is increasingly linked to liver disease, but the underlying mechanisms remain unclear. Here we show that chronic stress disrupts a brain–liver circuit that impairs hepatic CD8⁺ T cell immunity and accelerates liver cancer progression. Using both oncogene-driven and carcinogen-driven liver cancer models in male mice, we find that psychological stress disrupts catecholamine/β2-adrenergic receptor (ADRB2) signalling, which suppresses the expression of quinolinate phosphoribosyl transferase (QPRT), an enzyme of the kynurenine pathway, in hepatocytes. QPRT loss diverts kynurenine metabolism away from nicotinamide adenine dinucleotide (NAD⁺) synthesis towards kynurenic acid (KA) accumulation. This shift results in mitochondrial impairment and reduced effector function of liver CD8⁺ T cells. We confirm that ADRB2/QPRT expression correlates with hepatic NAD⁺ and KA levels and with CD8⁺ T cell frequency and function in human liver tissues. Importantly, ADRB2/QPRT overexpression in hepatocytes, or nicotinamide administration, recovers CD8⁺ T cell function in stressed mice and reduces liver cancer progression. These findings identify a stress-responsive metabolic checkpoint in the liver that links the nervous system to immune surveillance and may be therapeutically targeted in liver cancers.

Emerging evidence demonstrates that chronic stress alters immunological, neurochemical, and endocrinological functions, thereby promoting tumor progression. However, the underlying metabolic mechanism of chronic stress in tumor progression is still elusive. Using multiomics analysis, we found that aminopeptidase N (ANPEP) was upregulated in tumors with chronic restraint, associating with the reprogramming of amino acid metabolism. Functional assays revealed that ANPEP promoted liver cancer growth and metastasis. Knockdown of ANPEP blocked chronic stress–induced liver cancer progression. Chronic stress–induced glucocorticoids promoted nuclear receptor subfamily 3 group C member 1 nuclear translocation to activate ANPEP transcription by directly binding to its promoter. Furthermore, ANPEP promotes glutathione synthesis, subsequently inhibiting ROS-induced ferroptosis. Mechanistically, ANPEP interacted with solute carrier family 3 member 2 (SLC3A2) to block membrane associated ring-CH-type finger 8–mediated lysosome-dependent degradation of SLC3A2, promoting intracellular l-cystine transport, thereby increasing glutathione synthesis. The combination of ANPEP silencing and sorafenib treatment showed a synergistic effect in inhibiting liver cancer progression. Finally, clinical data and mouse models demonstrated that chronic stress drove liver tumor progression via ANPEP-regulated SLC3A2. These findings reveal unanticipated communication between chronic stress and metabolic reprogramming during liver cancer progression, providing potential therapeutic implications for liver cancer.

T cell immunoglobulin and mucin domain–containing protein 3 (TIM-3) is an immune checkpoint that has critical roles in immune exhaustion. However, little is known about the mechanisms that regulate TIM-3 surface expression and turnover. Here, we report that human TIM-3 is palmitoylated by the palmitoyltransferase DHHC9 at residue cysteine 296 (Cys ²⁹⁶ ). Palmitoylation stabilized TIM-3 by preventing binding to E3 ubiquitin ligase HRD1, thereby suppressing its polyubiquitination and degradation. DHHC9 knockdown attenuated chimeric antigen receptor T (CAR-T) cell exhaustion, and a peptidic inhibitor of TIM-3 palmitoylation accelerated TIM-3 degradation and enhanced antitumor immunity mediated by CAR-T cells and natural killer (NK) cells. In hepatocellular carcinoma, DHHC9 expression correlated with TIM-3 expression in CD8 ⁺ T cells and NK cells, and high DHHC9 expression was associated with shorter survival in patients with high TIM-3. These findings demonstrate that palmitoylation of TIM-3 catalyzed by DHHC9 promotes its stability, resulting in immune exhaustion and impaired antitumor immunity.

Metabolic dysfunction-associated steatotic liver disease (MASLD) asscociated hepatocellular carcinoma (HCC) is becoming a growing concern in global healthcare. The early-life gut microbiota plays a crucial role in maintaining healthy. However, the impact of early-life gut microbiota dysbiosis on the advancement of MASLD-HCC remains inadequately understood. In the present study, we investigated the role of early-life gut microbiota in the development of MASLD-HCC in streptozotocin and high-fat diet (STZ-HFD) induced mouse model. We recorded the body weight and lifespan, and dynamically monitored the level of alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), total cholesterol (T-CHO) and blood glucose in the serum monthly. In addition, we examined various immune cells present in the liver, such as T cells, B cells, NK cells, NKT cells, αβT cells, γδT cells, macrophage and MDSC cells by flow cytometry and conducted liquid chromatography mass spectrometry (LC–MS) based analysis on liver tissue from control and early-life antibiotic exposure mice (early-Abx) MASLD-HCC mice. We found that early-Abx mice suffered from more severe tumor burden and further confirmed that hepatocytes and immune cells were all disturbed. Importantly, early-life antibiotic exposure alters the liver metabolic profiling especially glycerophospholipids and lipid accumulation. Furthermore, mice exposed to antibiotics in early-life showed disturbances in glucose metabolism and developed insulin resistance. Collectively, our findings revealed that early-life antibiotic exposure accelerated the progression of MASLD-HCC by impairing the hepatocytes, immune homeostasis and metabolites persistently, highlighting the importance of the early-life microbiota in the development of MASLD-HCC.