Altered immunophenotypic expression in the peripheral bladder cancer immune landscape

Treatments targeting the immune system only benefit a subset of patients with bladder cancer (BC). Biomarkers predictive of BC progression and response to specific therapeutic interventions are required. We evaluated whether peripheral blood immune subsets and expression of clinically relevant immune checkpoint markers are associated with clinicopathologic features of BC. Peripheral blood mononuclear cells isolated from blood collected from 23 patients with BC and 9 age-matched unaffected-by-cancer control donors were assessed using a 21-parameter flow cytometry panel composed of markers of T, B, natural killer and myeloid populations and immune checkpoint markers. Patients with BC had significantly lower numbers of circulating CD19⁺ B cells and elevated circulating CD4⁺CD8⁺ T cells compared with the control cohort. Immune checkpoint markers programmed cell death protein 1 (PD-1) and T-cell immunoglobulin and mucin-domain containing-3 (TIM-3) were elevated in the total peripheral immune cell population in patients with BC. Within the BC cohort, PD-1 expression in T and myeloid cells was elevated in muscle-invasive compared with non-muscle-invasive disease. In addition, elevated T, B and myeloid PD-1 cell surface expression was significantly associated with tumor stage, suggesting that measures of peripheral immune cell exhaustion may be a predictor of tumor progression in BC. Finally, positive correlations between expression levels of the various immune checkpoints both overall and within key peripheral blood immune subsets collected from patients with BC were observed, highlighting likely coregulation of peripheral immune checkpoint expression. The peripheral blood immunophenotype in patients with BC is altered compared with cancer-free individuals. Understanding this dysregulated immune profile will contribute to the identification of diagnostic and prognostic indicators to guide effective immune-targeted, personalized treatments.