Targeted activation of junctional adhesion molecule-like protein+ CD8+ T cells enhances immunotherapy in hepatocellular carcinoma.

OBJECTIVE: Cytotoxic T lymphocytes (CTLs) play a crucial role in the therapeutic approach to hepatocellular carcinoma (HCC). Recent research has indicated that junctional adhesion molecule-like protein (JAML) enhances the antitumor activity of CD8+ T cells. Our study investigates the role of JAML+ CD8+ T cells in HCC. METHODS: We utilized time-of-flight mass cytometry and an orthotopic mouse model of HCC to examine histone modifications in tumor-infiltrating immune cells undergoing immunotherapy. Flow cytometry was used to assess CD4+ T cells differentiation and JAML expression in CD8+ T cells infiltrating HCC. Correlation analysis revealed a strong positive correlation between lactate dehydrogenase A+ (LDHA+) CD4+ T cells and JAML+ CD8+ T cells. Subsequently, we evaluated the therapeutic effects of an agonistic anti-JAML antibody, both alone and combined with immunotherapy. Finally, RNA sequencing was conducted to identify potential regulatory mechanisms. RESULTS: Immunotherapy significantly increased the percentage of CD8+ T cells infiltrating HCC and induced histone modifications, such as H3K18 lactylation (H3K18la) in CD4+ T cells. Flow cytometry analysis revealed that lactate promotes the differentiation of CD4+ T cells into Th1 cells. LDHA, an enzyme that converts pyruvate to lactate, plays a key role in this process. Correlation analysis revealed a strong positive relationship between LDHA+ CD4+ T cells and JAML+ CD8+ T cells in patients who responded to immunotherapy. Moreover, high JAML expression in CD8+ T cells was associated with a more favorable prognosis. In vivo experiments demonstrated that agonistic anti-JAML antibody therapy reduced tumor volume and significantly prolonged the survival of tumor-bearing mice, independent of the effects of anti-programmed cell death protein ligand-1 antibody (αPD-L1)-mediated immunotherapy. Pathway enrichment analysis further revealed that JAML enhances CTL responses through the oxidative phosphorylation pathway. CONCLUSIONS: Activation of JAML enhances CTL responses in HCC treatment, independent of αPD-L1-mediated immunotherapy, providing a promising strategy for advanced HCC.