Lipopolysaccharide promotes bladder cancer immunosuppression by disrupting the Tfh/Tfr balance through TLR4 signaling.

OBJECTIVE: To investigate the role of lipopolysaccharide (LPS)-mediated toll-like receptor 4 (TLR4) signaling in modulating the tumor immune microenvironment, particularly the follicular helper T cell (Tfh)/follicular regulatory T cell (Tfr) equilibrium, in bladder cancer. METHODS: MBT-2 and MB49 cells were treated with LPS. TLR4 was knocked down using lentiviral short hairpin RNA. Cell proliferation, migration, and invasion were assessed by methylthiazolyldiphenyl-tetrazolium bromide, scratch, and Transwell assays. A subcutaneous xenograft model in C57BL/6 and C3H/He mice was established. Tfh/Tfr cells in spleens were analyzed by flow cytometry. TLR4 and related cytokine expression were measured by quantitative polymerase chain reaction and western blot. RESULTS: LPS treatment upregulated the expression of TLR4/myeloid differentiation primary response 88, which enhanced tumor cell proliferation and migration in vitro and promoted tumor growth in vivo. These pro-tumor effects were reversed by TLR4 knockdown. Furthermore, LPS skewed the Tfh/Tfr ratio in favor of Tfh cells. At the cytokine level, LPS increased the production of interleukin-21 but decreased the levels of forkhead box P3, interleukin-10, and transforming growth factor-beta. All these immunologic alterations were also abolished upon TLR4 knockdown. CONCLUSION: LPS exacerbated bladder cancer progression by activating TLR4 signaling. This disrupts the Tfh/Tfr balance and creates an immunosuppressive niche. Targeting this axis may represent a novel therapeutic strategy.