Di-2-ethylhexyl Phthalate Reprograms Epithelial-Mesenchymal Transition and Lenvatinib Responsiveness in Hepatoma Cells via SPAG4-Dependent MAPK/ERK Signaling.

Environmental chemical exposure has emerged as an important modulator of cancer progression and therapeutic outcomes. Di-2-ethylhexyl phthalate (DEHP), a ubiquitous environmental plasticizer, has been widely recognized for its endocrine-disrupting effects; however, its impact on intracellular signaling reprogramming and cancer drug responsiveness remains incompletely understood. In this investigation, we aimed to elucidate the toxicological mechanisms by which DEHP alters cellular phenotypes and therapeutic sensitivity in hepatocellular carcinoma (HCC) cells. We demonstrate that DEHP exposure does not primarily promote cancer cell proliferation but instead induces epithelial-mesenchymal transition (EMT), leading to enhanced migratory and invasive capacities and reduced responsiveness to the tyrosine kinase inhibitor lenvatinib. Notably, integrative bioinformatic analyses combined with functional validation identified sperm-associated antigen 4 (SPAG4) as a key DEHP-responsive regulator mediating toxicant-induced cellular reprogramming. Mechanistic studies revealed that DEHP-induced upregulation of SPAG4 activates the MAPK/ERK signaling pathway, thereby driving EMT and attenuating lenvatinib responsiveness. Genetic silencing of SPAG4 or pharmacological inhibition of MAPK/ERK signaling effectively reversed DEHP-induced EMT and drug resistance. In conclusion, we highlight DEHP as a signaling-disrupting environmental toxicant that reprograms cancer cell states and modulates therapeutic responses through a SPAG4-dependent MAPK/ERK pathway. These findings provide mechanistic insight into how environmental chemical exposure can reshape intracellular signaling networks and influence cancer treatment outcomes, underscoring a previously underappreciated aspect of chemical toxicology.