EZH2 inhibition triggers a context-specific ACSS2-H3K9ac-HK2 metabolic circuit in EZH2 non-mutant solid tumors.

BACKGROUND & OBJECTIVES: EZH2 inhibitors show limited efficacy in solid versus hematologic cancers, but the underlying mechanisms are unknown. We investigated whether tumor-type-specific adaptive responses underlie this differential sensitivity.

METHODS: Glycolytic and acetylation gene signatures were analyzed across multiple transcriptomic datasets. Findings were validated in a panel of solid tumor cell lines using transcriptomic, biochemical (WB, qPCR), cellular (flow cytometry, immunofluorescence), and mechanistic (Cut&Tag, ChIP-qPCR) approaches.

RESULTS: Cross-tumor analysis revealed that EZH2/PRC2 inhibition selectively upregulates glycolytic genes and HK2 in EZH2-wildtype solid tumors, distinguishing them from both EZH2-mutant and EZH2-wildtype hematologic malignancies. Time-course analysis confirmed that EZH2 inhibition (GSK126/Tazemetostat) induced progressive HK2 upregulation in the EZH2-wildtype solid tumor cell lines tested, but not in EZH2-mutant hematologic (SU-DHL-4) cells. GSK126 time-dependently increased lactate production in hypoxic B16-F10 cells, and lactate exacerbated Treg polarization under low-glucose conditions. In vivo, this aligned with increased intratumoral Treg infiltration and KI67/HK2 upregulation in GSK126-treated tumors. Dual EZH2/HK2 inhibition synergistically suppressed tumor growth, while reducing Treg accumulation. Mechanistic studies showed that EZH2 inhibition time-dependently upregulated H3K9ac in EZH2-non-mutant solid tumor cells, but not in SU-DHL-4 cells, with Cut&Tag and ChIP-qPCR confirming H3K9ac enrichment at the HK2 promoter in B16-F10 cells. Stratified analysis identified a metabolism-associated acetylation gene set (including ACSS2 and ACLY) as most significantly upregulated in EZH2-non-mutant solid tumors. Functional validation confirmed that EZH2 inhibition-induced HK2 upregulation correlated with ACSS2, but not ACLY, expression in EZH2-non-mutant solid tumor cells. The ACSS2-H3K9ac axis in HK2 regulation was further supported by the finding that ACSS2 knockdown or overexpression correspondingly altered HK2 and H3K9ac levels in a human EZH2-non-mutant solid tumor cell line. We further demonstrated that EZH2 inhibition reduces H3K27me3 enrichment at the ACSS2 promoter, leading to its transcriptional upregulation. Consequently, pharmacological inhibition of ACSS2 reversed GSK126-induced H3K9ac enrichment at the HK2 promoter, downregulated HK2 expression, and synergistically suppressed B16-F10 model growth.

CONCLUSION: We identified a novel ACSS2-H3K9ac-HK2 signaling axis that is characteristically activated in EZH2-non-mutant solid tumors and drives metabolic reprogramming and resistance to EZH2 inhibition.