Histone H3 lactylation drives chemotherapy-induced SASP in breast cancer cells: a multi-omics analysis

The senescence-associated secretory phenotype (SASP) is a major driver of chemotherapy-induced adverse effects in cancer therapy; however, its regulation through metabolic reprogramming in senescent cells remains poorly understood. In particular, the epigenetic mechanisms linking metabolic alterations to the chemotherapy-induced SASP have not been fully elucidated. In this study, metabolomic analysis demonstrated that chemotherapy-induced senescent breast cancer cells exhibit both enhanced respiratory potential and markedly increased lactate production. Genetic ablation or pharmacological inhibition of lactate dehydrogenase A (LDHA) significantly attenuated SASP expression. Moreover, LDHA depletion impaired the capacity of senescent cells to stimulate mammary tumor growth and inhibit dendritic cell (DC) infiltration within a co-inoculation xenograft model. Mechanistically, a screen of nine metabolism-related lysine post-translational modifications revealed a global increase in lysine lactylation (Kla) within senescent cells, with H3K9la, H3K14la, and H3K18la being significantly upregulated. Integrated CUT&Tag-seq and ATAC-seq analyses identified increased enrichment of H3K9la and H3K18la at SASP gene loci, coinciding with enhanced chromatin accessibility at their respective promoters. Finally, we identified general control nonderepressible 5 (GCN5) and P300/CBP-associated factor (PCAF) as lactyltransferases in senescent cells; either knockdown or pharmacological inhibition of GCN5 or PCAF reduced H3K9la and H3K18la levels, subsequently suppressing SASP transcription and secretion. Collectively, our findings delineate the metabolic landscape of senescent breast cancer cells and establish a mechanistic framework linking lactate production, histone H3 lactylation, and SASP regulation.