Paeonol Suppresses Bladder Cancer Progression via Apoptotic Pathways: Insights from In Vitro and In Vivo Studies

Background/Objectives: Bladder cancer (BC), a highly heterogeneous and mutation-prone malignancy, remains a significant therapeutic challenge due to its propensity for recurrence, metastasis, and drug resistance. Natural products, particularly paeonol, a bioactive compound derived from Moutan Cortex in traditional Chinese medicine, have shown promising potential in cancer therapy. This study aims to evaluate the anti-BC effects of paeonol and elucidate its underlying molecular mechanisms. Methods: In vitro experiments were conducted using T24 and J82 BC cell lines to assess paeonol's effects on cell viability, migration, apoptosis, and cell cycle progression via CCK-8, scratch, flow cytometry, RT-qPCR, and Western blot analyses. In vivo efficacy was evaluated using a xenograft mouse model, with tumor growth monitored and histopathological analysis performed. Results: Paeonol significantly inhibited BC cell proliferation and migration in a dose- and time-dependent manner, with IC₅₀ values of 225 μg/mL (T24) and 124 μg/mL (J82) at 48 h. It induced apoptosis and arrested the cell cycle at the G1 phase, accompanied by upregulation of pro-apoptotic proteins (BID, BAX, BIM, and p53). In vivo, paeonol reduced tumor volume and weight without histopathological abnormalities in vital organs. Conclusions: Paeonol exhibits potent anti-BC activity by apoptotic pathways and by arresting the cell cycle at the G1 phase and inhibiting tumor growth. Its favorable safety profile and multi-target mechanisms highlight its potential as a promising therapeutic candidate for BC. These findings provide a foundation for further clinical development of paeonol-based therapies.