Targeting FOXM1 condensates reduces breast tumour growth and metastasis.

Identifying phase-separated structures remains challenging, and effective intervention methods are currently lacking. Here we screened for phase-separated proteins in breast tumour cells and identified forkhead (FKH) box protein M1 (FOXM1) as the most prominent candidate. Oncogenic FOXM1 underwent liquid-liquid phase separation (LLPS) with FKH consensus DNA element, and compartmentalized the transcription apparatus in the nucleus, thereby sustaining chromatin accessibility and super-enhancer landscapes crucial for tumour metastatic outgrowth. Screening an epigenetics compound library identified AMPK agonists as suppressors of FOXM1 condensation. AMPK phosphorylated FOXM1 in the intrinsically disordered region (IDR), perturbing condensates, reducing oncogenic transcription, accumulating double-stranded DNA to stimulate innate immune responses, and endowing discrete FOXM1 with the ability to activate immunogenicity-related gene expressions. By developing a genetic code-expansion orthogonal system, we demonstrated that a phosphoryl moiety at a specific IDR1 site causes electrostatic repulsion, thereby abolishing FOXM1 LLPS and aggregation. A peptide targeting IDR1 and carrying the AMPK-phosphorylated residue was designed to disrupt FOXM1 LLPS and was shown to inhibit tumour malignancy, rescue tumour immunogenicity and improve tumour immunotherapy. Together, these findings provide novel and in-depth insights on function and mechanism of FOXM1 and develop methodologies that hold promising implications in clinics.