Metformin Shows Promise in Treating Bladder Cancer, Reduces PD-L1 Expression

Research has shed new light on the potential of metformin, a medication commonly used to treat diabetes, in combating bladder cancer. A study published in BMC Cancer found that metformin can suppress bladder cancer cell proliferation and prolong survival in an orthotopic mouse model. The study's findings suggest that metformin's therapeutic effects are linked to its ability to downregulate PD-L1 expression, a crucial immune checkpoint protein that limits the effectiveness of antitumor immunity.

Key Takeaways:

• Metformin, a commonly used antidiabetic agent, has been shown to have anti-cancer properties in bladder cancer cells.
• The study employed a syngeneic orthotopic bladder cancer model with immunocompetent C57BL/6 mice to evaluate metformin's therapeutic effects.
• Metformin reduced cancer cachexia, tumor size, and improved survival at a safe dosage of 150 mg/kg/day.
• Metformin attenuated tumor-induced PD-L1 upregulation in a dose-dependent manner.
• The study's findings suggest that metformin's therapeutic effects are linked to its ability to downregulate PD-L1 expression.
• Although metformin has shown promise in treating bladder cancer, the exact mechanisms by which it exerts its effects remain unclear.
• The study's lead author, Pei-Chu Tsai, commented on the study's findings, stating that "metformin effectively downregulates PD-L1 expression, suppresses bladder cancer cell proliferation, and prolongs survival in an orthotopic bladder cancer mouse model."

Statistics:

• The study used a maximum tolerated dose (MTD) test to establish a safe dosage of metformin, identifying 150 mg/kg/day as suitable.
• At this dosage, metformin reduced cancer cachexia, tumor size, and improved survival in the mouse model.
• The study reported a significant reduction in PD-L1 expression in mouse bladder cancer tissues treated with metformin.
• The study's findings suggest that metformin's therapeutic effects are linked to its ability to downregulate PD-L1 expression, which is a critical immune checkpoint protein.

Sources:

• Tsai, P-C., et al. "Metformin as an anti-cancer agent against bladder cancer acts via PD-L1 downregulation in an orthotopic mouse model." BMC Cancer, vol. 25, no. 1, 2025, p. 1534.
• "Findings from National Institute of Infectious Diseases and Vaccinology Broadens Understanding of Bladder Cancer (Metformin as an anti-cancer agent against bladder cancer acts via PD-L1 downregulation in an orthotopic mouse model)." Cancer Weekly, October 21, 2025, p. 143.