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.