Tumour-associated B cells in urothelial urinary bladder cancer

Tumour infiltrating B cells and CD38⁺ plasma cells have been correlated with survival in different malignancies but their role in urinary bladder cancer is unclear. IL-10 is a multifunctional cytokine with both anti-inflammatory and immunostimulatory properties, that can be released by regulatory B cells (Bregs). We have stained paraffin-embedded tumour sections from 31 patients with invasive urothelial urinary bladder cancer with respect to CD20⁺ B cells, CD38⁺ cells, IL-10-expressing cells, IgG, C1q and C3a and analysed the impact of these markers on survival. Interestingly, we observe tumour-associated CD20⁺ B cells forming follicle-like structures in tumours of some patients. We demonstrate that follicle-like structures, tumour-associated CD38⁺ cells, IL-10 produced by non-B cells, tumour infiltrating IgG and activation of the complement system, may associate to longer survival of urinary bladder cancer patients. IL-10 expression by tumour-associated Bregs may instead negatively affect prognosis. More research is needed to fully understand the role of B cells and IL-10 in urinary bladder cancer.