Dibutyl phthalate at environmentally relevant concentrations promotes hepatocellular carcinoma progression via stabilization of hepatocyte-derived Lipocalin-2

DBP-orchestrated liver transcriptional targets are largely associated with HCC. • DBP stabilizes hepatocyte-derived LCN2 to activate cancer cell proliferation. • 24p3R-MMP-9 axis is involved in such a LCN2-triggered cancer cell activation. • Stable DBP-LCN2 complex formation prevents ubiquitin-mediated degradation of LCN2. Dibutyl phthalate (DBP) is a ubiquitous environmental contaminant whose exposure is positively associated with the progression of metabolic dysfunction-associated steatotic liver disease (MASLD). However, the underlying mechanisms by which DBP promotes MASLD progression remain unclear. In this study, high-throughput RNA sequencing revealed that the DBP-orchestrated liver transcriptome is enriched in target clusters associated with hepatocellular carcinoma (HCC), an advanced complication of MASLD. DBP promotes HCC progression in murine models but does not directly affect HCC cell proliferation, indicating that hepatocytes may be the primary target cells for DBP signaling. To identify a molecular target in hepatocytes that transduces DBP signals to HCC cells, we performed label-free proteomic analyses, molecular docking, and the Cancer Genome Atlas (TCGA) database analyses, which identified hepatocyte-derived lipocalin-2 (LCN2) as a candidate target of DBP. Elevated LCN2 expression is negatively associated with overall survival in HCC patients. Inhibition of LCN2 partially attenuates the tumor-promoting effect of DBP-treated hepatocytes on HCC cells. Mechanistically, molecular docking and molecular dynamics simulations demonstrate that DBP directly binds to LCN2 to form a stable complex, which disrupts ubiquitin-proteasome-mediated degradation of LCN2 and thereby enhances its protein stability. Functionally, hepatocyte-derived LCN2 promotes HCC cell proliferation through activation of the 24p3R–matrix metalloproteinase-9 (MMP-9) signaling axis. Our findings demonstrate that DBP acts as a progression promoter in pre-existing HCC via hepatocyte LCN2 stabilization, rather than an initiator of hepatocarcinogenesis. This mechanistic insight addresses a critical gap in understanding how environmental toxicants modulate established HCC progression, complementing epidemiological associations between phthalates and liver disease. Download: Download high-res image (228KB) Download: Download full-size image