Transcriptomic profiling of T-cell populations in non-muscle invasive and muscle invasive bladder cancer.

Background: Bladder cancer is categorized as non-muscle invasive (NMIBC) or muscle invasive (MIBC). NIMBC makes up around 70% of the cases and although it is less aggressive, the recurrence rate is 50-70%, thus requiring extensive monitoring. Additionally, there is a risk of progression into MIBC with a 5-year survival of only 50% even when treated with radical cystectomy. Immune checkpoint inhibitors have shown promising results for treatment of bladder cancer; however, only around 30% of patients have a therapeutic effect and novel therapies are thus required. With the aim of pinpointing novel targets for T-cell based therapy, we have performed transcriptomic profiling of specific T cell populations in MIBC and NMIBC, as well as in control bladder tissue.
Methods: Muscle-invasive (n=7) as well as non-muscle invasive (n=13) bladder tumor biopsies were obtained from untreated patients and control bladder tissue (n=7). Upon digestion, cells were stained with an antibody panel to enable sorting of CD8+ cytotoxic T-cells (CD8T), CD4+ T-helper cells (Th) and regulatory T-cells (Treg) using fluorescence activated cell sorting. RNA was extracted and subject to sequencing. Differential gene expression analysis was performed, using DESeq2 (genes with padjResults: Principal component analysis demonstrated that CD8T, unlike Th and Tregs, cluster according to the invasiveness of the disease. Accordingly, many genes were significantly differentially expressed between CD8T in MIBC and NMIBC compared to control, and also between CD8T in MIBC compared to NMIBC. Several genes associated with CD8 T-cell exhaustion were significantly upregulated in MIBC compared to both NMIBC and control. Further, GSEA results indicated biological differences of the CD8T compartment between different tumor stages.
Conclusion: The gene expression profiles of CD8 T-cells were significantly different in NMIBC, MIBC and control. The transcriptional profiles give clues on biological differences and disease progression and can be relevant for development of novel treatment strategies.