Histone H4K8 lactylation modulated immunosuppressive properties by promoting FAP transcription and ECM remodeling.

BACKGROUND & AIMS: The role of histone lysine lactylation (Kla) in gastric cancer mesenchymal stromal cells (GCMSCs) remains elusive. This study aimed to investigate the potential lactyltransferase and the influence of histone Kla in GCMSCs.

METHODS

Histone Kla levels in GCMSCs were characterized by cell immunofluorescence and Western blotting. The transcriptional regulation was validated via CUT&Tag sequencing coupled with qPCR analysis. Immunosuppressive effectors through Western blotting and multiplex immunohistochemistry (mIHC). β-alanine and AZD3965 were applied to inhibit histone Kla in vitro. Ultimately, β-alanine was selected for its ability to enhance the efficacy of anti-PD-1 therapy in NCGPBMC tumor-bearing model.

RESULTS

The primary GCMSCs exhibited higher histone Kla levels. Lactate treatment triggered the nuclear translocation of aminoacyl-tRNA synthetase 1 (AARS1), whose knockdown attenuated lactate-driven nuclear accumulation and suppressed histone Kla. CUT&Tag-qPCR analysis revealed lactate-induced Pan-Kla enrichment at the FAP promoter, driving extracellular matrix (ECM) receptor interaction pathways. Deeply, H4K8 lactylation (H4K8la) has been defined as the key regulatory role to promote FAP transcription, corroborated by mIHC mapping of their immune-excluded spatial organization. In NCGPBMC tumor-bearing models, β-alanine synergized with anti-PD-1 therapy, enhancing tumor regression and augmenting CD8⁺ T cell effector functions.

CONCLUSIONS

We elucidate a Kla-dependent mechanism underlying GCMSCs-mediated ECM remodeling and immunosuppressive niche formation. The results provide novel insights into the epigenetic regulation of immunosuppressive TME.