Urine-derived lymphocytes as a non-invasive measure of the bladder tumor immune microenvironment

Despite the advances in cancer immunotherapy, only a fraction of patients with bladder cancer exhibit responses to checkpoint blockade, highlighting a need to better understand drug resistance and identify rational immunotherapy combinations. However, accessibility to the tumor prior and during therapy is a major limitation in understanding the immune tumor microenvironment (TME). Herein, we identified urine-derived lymphocytes (UDLs) as a readily accessible source of T cells in 32 patients with muscle invasive bladder cancer (MIBC). We observed that effector CD8(+) and CD4(+) cells and regulatory T cells within the urine accurately map the immune checkpoint landscape and T cell receptor repertoire of the TME. Finally, an increased UDL count, specifically high expression of PD-1 (PD-1(hi)) on CD8+ at the time of cystectomy, was associated with a shorter recurrence-free survival. UDL analysis represents a dynamic liquid biopsy that is representative of the bladder immune TME that may be used to identify actionable immuno-oncology (IO) targets with potential prognostic value in MIBC.