AF9/KLF2 gene regulatory circuit links histone lactylation to breast cancer metastasis

Histone lysine L-lactylation (hereafter referred to as histone Kla) is a novel epigenetic mark induced by glycolytic metabolism, serving as a link between metabolic reprogramming and epigenetic regulation. In this study, we uncover an epigenetic-genetic transcriptional regulatory circuit involving AF9 and KLF2 that drives luminal breast cancer progression. AF9, identified as a reader of histone H3 lysine 9 lactylation (H3K9la), promotes KLF2 expression, while KLF2, functioning as a transcription factor for AF9, forms a positive feedback loop that amplifies lactylation-dependent effects. This circuit activates tumor-associated pathways, including TGFβ1, glucose and lactate transporters, and metabolic enzymes essential for glycolysis and serine biosynthesis, driving tumorigenesis and metastasis. Spatial and single-cell transcriptomics show AF9-positive tumor cells enriched in regions of active lactylation, correlated with immune evasion through interactions with M2 macrophages. Together, AF9, H3K9la, and KLF2 integrate metabolism, epigenetics, and signaling to promote tumor growth and metastasis, highlighting AF9’s central role as a histone lactylation reader and a potential therapeutic target in breast cancer.