Malignant Transformation of Human Uroepithelial Cells Induced by Long-Term Exposure to a Disinfection Byproduct─2,6-Dichlorobenzoquinone

Halobenzoquinones (HBQs), a class of water disinfection byproducts (DBPs), have emerged as potential bladder carcinogens. However, evidence regarding the long-term health effects of HBQ exposure and their potential to induce malignant transformation remains limited. Here, we examined the chronic effects of 2,6-dichlorobenzoquinone (2,6-DCBQ) exposure on human immortalized uroepithelial cells (SV-HUC-1), with a focus on malignant transformation. Cells were continuously exposed to a noncytotoxic concentration of 2,6-DCBQ for over three months. The long-term transformed cells exhibited cellular and nuclear pleomorphism and anchorage-independent cell growth─a hallmark of cancer cell transformation. Proteomic analysis identified 60 differentially expressed proteins (DEPs), 20 of which are strongly associated with specific pathways of urinary bladder and urothelial cells. Enrichment analysis highlighted the actin cytoskeleton and extracellular matrix (ECM)–receptor interaction pathways. These molecular changes were supported by immunofluorescence assay, revealing filamentous actin disorganization and vinculin mislocalization in 2,6-DCBQ-treated cells. Together, these results suggest that cytoskeletal destabilization and adhesion collapse are key features associated with 2,6-DCBQ-induced malignant transformation, indicating that chronic exposure to low-level waterborne HBQs is associated with human bladder carcinogenesis.