Immunoproteomics of Lymph Node T-cells in Bladder Cancer

The immune-suppressive features often possessed by invasive tumors hamper effective anti-tumor immunity. In this context, tumor-infiltrating regulatory T cells (Tregs) have been widely implied, principally as unwanted suppressors of anti-tumor immune responses. However, while many studies have focused on tumor-infiltrating Tregs, the function and signaling of Tregs in tumor-associated lymph nodes is largely unknown. In this study, we set out to clarify how immune signaling in lymph nodes is impacted by its contact to the tumour. Because muscle-invasive urothelial bladder cancer (MIBC) represent an immunogenic cancer were Tregs are accumulated and sentinel nodes (SNs) can be efficiently detected, we explored the protein expression of T-cells in SNs and non-SNs of MIBC patients. Proteomic analysis of Tregs and effector T-cells in SN and non-draining lymph nodes found SN-Tregs in MIBC patients to up-regulate growth and immune signaling pathways, the cytokine IL-16 being central in the signaling network. Experimental validation showed that in Tregs, tumoral factors increase IL-16 processing into bioactive forms and increase FOXP3 expression. In conclusion, altered IL-16 processing caused by tumour-released factors stimulate expansion of SN-Tregs in MIBC, creating an immunosuppressive environment and contributing to immune escape.