Cholesterol-metabolic TAMs regulates tumor budding like cell subpopulation to promote chordoma stemness via BACH1/ANGPTL4/SDC4 axis

Abstract Background Tumor budding (TB) is a well established prognostic indicator in various epithelial malignancies. Chordoma, although a rare mesenchymal tumor, paradoxically exhibits prominent epithelial-like characteristics, as demonstrated in previous studies. In particular, it remains unclear whether TB like (TBL) structures are present in chordoma, as well as the molecular mechanisms driving their formation and their functional impact on tumor progression, representing a critical gap in current knowledge. Methods TBL grades were defined and evaluated in tumor specimens from 481 chordoma patients across four large cohorts using hematoxylin-eosin and immunohistochemical staining. Multi-omics profiling, encompassing GeoMx digital spatial profiling, spatial transcriptomics, bulk RNA sequencing, single-cell RNA sequencing, single-cell ATAC sequencing, and multiplex quantitative immunofluorescence, was integrated to delineate TBL cell subpopulation (TBLCs) and their interactions with cholesterol-metabolic tumor-associated macrophages (CM-TAMs). Organoid models and in vitro/in vivo functional assays were employed for mechanistic investigation and validation. Results TBL structures were prevalent in chordoma, and higher TBL grades were associated with unfavorable clinical outcomes and aggressive phenotypes. Mechanistically, BACH1 in CM-TAMs drove ANGPTL4 secretion, which targeted the SDC4 receptor on TBLCs, thereby enhancing stem-like properties, promoting cholesterol accumulation, and accelerating malignant progression. Pharmacological inhibition of cholesterol metabolism or disruption of the BACH1-ANGPTL4-SDC4 signaling axis markedly reduced tumor invasiveness in both preclinical models and chordoma organoids. Conclusions BACH1-driven CM-TAMs activate TBLCs via the ANGPTL4-SDC4 signaling axis, promoting stemness and cholesterol accumulation, ultimately driving malignant progression in chordoma. These findings uncover a previously unrecognized tumor–immune–metabolic interaction and suggest potential therapeutic targets for this disease.