Exploring the Anticancer Potential of the Multistrain Probiotic Formulation OxxySlab in Bladder Cancer Cell Lines

Bladder cancer (BC), particularly its muscle-invasive subtype (MIBC), remains a clinical challenge due to high recurrence and limited therapeutic options. Emerging evidence suggests that probiotics may offer selective anticancer effects while preserving healthy tissue. In this study, we evaluated the antitumor potential of <i>OxxySlab</i>, a multistrain probiotic formulation, in two BC cell lines (T24 and 5637) and a non-tumorigenic urothelial cell line (SV-HUC1). <i>OxxySlab</i> lysate dose-dependently inhibited BC cell proliferation, clonogenicity, and migration, while sparing normal cells. Mechanistically, the treatment suppressed epithelial-mesenchymal transition (EMT), induced senescence, and disrupted redox homeostasis in malignant cells. These effects were associated with the induction of oxidative stress and impaired antioxidant defenses. Co-treatment with vitamin C attenuated ROS accumulation and senescence, implicating oxidative stress as a key mediator. Notably, SV-HUC1 cells retained viability and phenotype, confirming the formulation's selectivity. Overall, these findings support <i>OxxySlab</i> as a promising adjunctive strategy in BC therapy, capable of reducing tumor aggressiveness through redox-mediated senescence and EMT inhibition without harming normal urothelial cells.