Investigation of carcinogenic effects of polystyrene microplastic on human bladder cancer cells

Plastic pollution has become a global environmental problem. Humans are increasingly exposed to microplastics (MPs) and nano-plastics (NPs) through ingestion, inhalation, and skin contact. These particles may affect organs such as the brain, liver, kidneys, and bladder by triggering inflammation, altering immune responses, and disrupting the urothelial barrier-an established risk factor for bladder cancer and interstitial cystitis. We investigated the uptake of micro (0.5 µm) and nano-plastic (0.03 µm) polystyrene microplastics by human bladder cancer cell lines (SW-78 and UMUC-3). Both cell lines showed altered proliferation compared with controls. SW-78 cells responded significantly to 8,000, 16,000, and 32,000 p/mL, while 64,000 p/mL was toxic to cell proliferation. In UMUC-3 cells, proliferation increased at all concentrations in a time-dependent manner. Moreover, cell migration in UMUC-3 cells was not significantly influenced by 0.03 µm PS particles compared with controls, whereas 0.5 µm PS particles affected migration. In SW-78 cells, migration was significantly induced by lower concentrations of 0.03 µm particle but was significantly reduced at 64,000 p/mL. We also confirmed that higher doses of plastic particles caused significant DNA damage and ROS production in a concentration-dependent manner. PS particles showed strong attachment of MPs to the cell surface in live-cell imaging, while confocal imaging confirmed uptake, cytoplasmic accumulation, and nuclear translocation of the PS particles. Our findings suggest that PS microplastics influence bladder cancer cell proliferation and migration in a dose- and size-dependent manner, consistent with mechanisms involved in cancer progression. The presence of microplastics in the cytoplasm is likely to disrupt cellular metabolic processes, warranting further investigation. Given the rise in plastic pollution, microplastics may represent emerging risk factors for bladder cancer, underscoring the need for thorough toxicological and epidemiological studies.