Integrated Network Toxicology and Multi-Level Validations Unravel the Potential Mechanism Linking Phthalate Ester Exposure and Endocrine Diseases

Phthalate esters (PAEs) are endocrine-disrupting chemicals that can imitate endogenous hormones to disrupt the endocrine system. However, the upstream molecular initiating events (MIEs) by which PAEs trigger endocrine diseases, especially their interactions with receptor tyrosine kinases (RTKs), remain poorly understood. Here, we discovered that the targets of low molecular weight (LMW) and high molecular weight (HMW) PAEs highly overlapped with breast cancer-related targets, with an even greater overlap for HMW PAEs. Mechanistically, PAEs promoted breast cancer progression by activating the epidermal growth factor receptor (EGFR)-mediated signaling pathway, with EGFR identified as a key kinase. Molecular interaction analysis confirmed that PAEs directly bind to EGFR, inducing its dimerization, with the benzene ring, ketone, methyl, and ether groups of PAEs being crucial. Notably, HMW PAEs exhibited stronger dimerization effects. This PAE-induced EGFR dimerization was determined to be the MIE in PAE-induced breast cancer. Furthermore, PAEs increased EGFR expression (2.44-fold), subsequently activating the PI3K-Akt signaling pathway, which promoted breast cancer cell proliferation to 165.34% and tumor growth to 229.05% of the control, with HMW PAEs again having stronger effects. This study identifies a previously unrecognized MIE–PAE-induced EGFR dimerization, linking PAE exposure to RTK–driven breast cancer and offering potential targets for prevention and intervention in breast cancer.